[PATCH v7 00/11] Multi-phase reset mechanism

[PATCH v7 00/11] Multi-phase reset mechanism

[Damien Hedde]

Hi all,

The purpose of this series is to split the current reset procedure
into multiple phases. This will help to solve some ordering
difficulties we have during reset.

This is a ready to merge version. I've rebased on master and followed
Richard's remarks on v6. All patches have been reviewed by.

This series adds resettable interface and transitions base Device and
Bus classes (sysbus subclasses are ok too). It provides new reset
functions but does not switch anymore the old functions
(device_reset() and qdev/qbus_reset_all()) to resettable interface.
These functions keep the exact same behavior as before.

The series also transition the main reset handlers registration which
has no impact until devices and buses are transitioned.

The series is organized as follows:
Patch 1 is unmodified. Patch 2 adds some utility trace events.
Patches 3 to 8 adds resettable api in devices and buses. Patch 9 adds
some documentation. Patches 10 and 11 transition the call sites of
qemu_register_reset(qdev/qbus_reset_all_fn, ...).

After this series, the plan is then to transition devices, buses and
legacy reset call sites. Devices and buses have to be transitioned
from mother class to daughter classes order but until the final
(daughter) class is transitioned, old monolitic reset behavior will
be kept for this class.

Thanks,
Damien

v7:
  + patch 1
    - new device_reset occurrence (rebase)
  + patch 3
    - ResettablePhases un-nest (Richard)
    - warnings (Richard)
  + patch 7
    - inline resettable_state_clear (Richard)

v6:
https://lists.gnu.org/archive/html/qemu-devel/2019-12/msg04664.html
  + patch 1
    - update (microvm machine) (rebase)
  + patch 2
    - added more info in trace_qdev_update_parent_bus (Philippe)
  + patch 3
    - typos (Peter)
    - missing gpl header in header (Peter)
    - clarify global entry_in_progress flag (Peter)
  + patch 4
    -  parent/child terminology (Peter)
  + patch 5
    - typos (Peter)
    - comment about global exit_in_progress flag (Peter)
  + patch 6
    -  update list of qdev_set_parent_bus() call sites (rebase)
  + patch 7
    - clear reset state in realize before doing the hotplug reset
  + patch 9
    - added entry in index.rst
    - fix commit message and various improvements (Peter)
    - do parent phase method before child actions (Peter)
    - clarify "Polling the reset state" paragraph 
  + patch 12&13
    - removed (follow-up series to cleanup the raspi sd)

v5:
https://lists.gnu.org/archive/html/qemu-devel/2019-10/msg04730.html
  + various improvement in the resettable interface (regarding
    transition, robustness and several reset types)
  + better handling of transition from legacy reset to resettable
  + device hotplug and parent bus 'hot' change support
  + improved doc with examples and converted to rst format

v4:
https://lists.gnu.org/archive/html/qemu-devel/2019-08/msg04359.html

Damien Hedde (11):
  add device_legacy_reset function to prepare for reset api change
  hw/core/qdev: add trace events to help with resettable transition
  hw/core: create Resettable QOM interface
  hw/core: add Resettable support to BusClass and DeviceClass
  hw/core/resettable: add support for changing parent
  hw/core/qdev: handle parent bus change regarding resettable
  hw/core/qdev: update hotplug reset regarding resettable
  hw/core: deprecate old reset functions and introduce new ones
  docs/devel/reset.rst: add doc about Resettable interface
  vl: replace deprecated qbus_reset_all registration
  hw/s390x/ipl: replace deprecated qdev_reset_all registration

 docs/devel/index.rst     |   1 +
 docs/devel/reset.rst     | 289 +++++++++++++++++++++++++++++++++++++
 Makefile.objs            |   1 +
 include/hw/qdev-core.h   |  58 +++++++-
 include/hw/resettable.h  | 247 ++++++++++++++++++++++++++++++++
 hw/audio/intel-hda.c     |   2 +-
 hw/core/bus.c            | 102 +++++++++++++
 hw/core/qdev.c           | 160 +++++++++++++++++++--
 hw/core/resettable.c     | 301 +++++++++++++++++++++++++++++++++++++++
 hw/hyperv/hyperv.c       |   2 +-
 hw/i386/microvm.c        |   2 +-
 hw/i386/pc.c             |   2 +-
 hw/ide/microdrive.c      |   8 +-
 hw/intc/spapr_xive.c     |   2 +-
 hw/ppc/pnv_psi.c         |   4 +-
 hw/ppc/spapr_pci.c       |   2 +-
 hw/ppc/spapr_vio.c       |   2 +-
 hw/s390x/ipl.c           |  10 +-
 hw/s390x/s390-pci-inst.c |   2 +-
 hw/scsi/vmw_pvscsi.c     |   2 +-
 hw/sd/omap_mmc.c         |   2 +-
 hw/sd/pl181.c            |   2 +-
 vl.c                     |  10 +-
 hw/core/Makefile.objs    |   1 +
 hw/core/trace-events     |  27 ++++
 tests/Makefile.include   |   1 +
 26 files changed, 1211 insertions(+), 31 deletions(-)
 create mode 100644 docs/devel/reset.rst
 create mode 100644 include/hw/resettable.h
 create mode 100644 hw/core/resettable.c

-- 
2.24.1

[PATCH v7 01/11] add device_legacy_reset function to prepare for reset api change

[Damien Hedde]

Provide a temporary device_legacy_reset function doing what
device_reset does to prepare for the transition with Resettable
API.

All occurrence of device_reset in the code tree are also replaced
by device_legacy_reset.

The new resettable API has different prototype and semantics
(resetting child buses as well as the specified device). Subsequent
commits will make the changeover for each call site individually; once
that is complete device_legacy_reset() will be removed.

Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Acked-by: David Gibson <david@gibson.dropbear.id.au>
Acked-by: Cornelia Huck <cohuck@redhat.com>
---
v7 update: added new occurence due to rebase

Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Daniel P. Berrangé" <berrange@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
Cc: John Snow <jsnow@redhat.com>
Cc: "Cédric Le Goater" <clg@kaod.org>
Cc: Collin Walling <walling@linux.ibm.com>
Cc: Cornelia Huck <cohuck@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Halil Pasic <pasic@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Dmitry Fleytman <dmitry.fleytman@gmail.com>
Cc: Fam Zheng <fam@euphon.net>
---
 include/hw/qdev-core.h   | 4 ++--
 hw/audio/intel-hda.c     | 2 +-
 hw/core/qdev.c           | 6 +++---
 hw/hyperv/hyperv.c       | 2 +-
 hw/i386/microvm.c        | 2 +-
 hw/i386/pc.c             | 2 +-
 hw/ide/microdrive.c      | 8 ++++----
 hw/intc/spapr_xive.c     | 2 +-
 hw/ppc/pnv_psi.c         | 4 ++--
 hw/ppc/spapr_pci.c       | 2 +-
 hw/ppc/spapr_vio.c       | 2 +-
 hw/s390x/s390-pci-inst.c | 2 +-
 hw/scsi/vmw_pvscsi.c     | 2 +-
 hw/sd/omap_mmc.c         | 2 +-
 hw/sd/pl181.c            | 2 +-
 15 files changed, 22 insertions(+), 22 deletions(-)

diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
index 1518495b1e..b8341b0fb0 100644
--- a/include/hw/qdev-core.h
+++ b/include/hw/qdev-core.h
@@ -427,11 +427,11 @@ char *qdev_get_own_fw_dev_path_from_handler(BusState *bus, DeviceState *dev);
 void qdev_machine_init(void);
 
 /**
- * @device_reset
+ * device_legacy_reset:
  *
  * Reset a single device (by calling the reset method).
  */
-void device_reset(DeviceState *dev);
+void device_legacy_reset(DeviceState *dev);
 
 void device_class_set_parent_reset(DeviceClass *dc,
                                    DeviceReset dev_reset,
diff --git a/hw/audio/intel-hda.c b/hw/audio/intel-hda.c
index 6ecd383540..27b71c57cf 100644
--- a/hw/audio/intel-hda.c
+++ b/hw/audio/intel-hda.c
@@ -1087,7 +1087,7 @@ static void intel_hda_reset(DeviceState *dev)
     QTAILQ_FOREACH(kid, &d->codecs.qbus.children, sibling) {
         DeviceState *qdev = kid->child;
         cdev = HDA_CODEC_DEVICE(qdev);
-        device_reset(DEVICE(cdev));
+        device_legacy_reset(DEVICE(cdev));
         d->state_sts |= (1 << cdev->cad);
     }
     intel_hda_update_irq(d);
diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index 9f1753f5cf..8c0c8284c8 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -298,7 +298,7 @@ HotplugHandler *qdev_get_hotplug_handler(DeviceState *dev)
 
 static int qdev_reset_one(DeviceState *dev, void *opaque)
 {
-    device_reset(dev);
+    device_legacy_reset(dev);
 
     return 0;
 }
@@ -895,7 +895,7 @@ static void device_set_realized(Object *obj, bool value, Error **errp)
             }
         }
         if (dev->hotplugged) {
-            device_reset(dev);
+            device_legacy_reset(dev);
         }
         dev->pending_deleted_event = false;
 
@@ -1127,7 +1127,7 @@ void device_class_set_parent_unrealize(DeviceClass *dc,
     dc->unrealize = dev_unrealize;
 }
 
-void device_reset(DeviceState *dev)
+void device_legacy_reset(DeviceState *dev)
 {
     DeviceClass *klass = DEVICE_GET_CLASS(dev);
 
diff --git a/hw/hyperv/hyperv.c b/hw/hyperv/hyperv.c
index da8ce82725..8ca3706f5b 100644
--- a/hw/hyperv/hyperv.c
+++ b/hw/hyperv/hyperv.c
@@ -140,7 +140,7 @@ void hyperv_synic_reset(CPUState *cs)
     SynICState *synic = get_synic(cs);
 
     if (synic) {
-        device_reset(DEVICE(synic));
+        device_legacy_reset(DEVICE(synic));
     }
 }
 
diff --git a/hw/i386/microvm.c b/hw/i386/microvm.c
index 827ce29e58..d23485108d 100644
--- a/hw/i386/microvm.c
+++ b/hw/i386/microvm.c
@@ -370,7 +370,7 @@ static void microvm_machine_reset(MachineState *machine)
         cpu = X86_CPU(cs);
 
         if (cpu->apic_state) {
-            device_reset(cpu->apic_state);
+            device_legacy_reset(cpu->apic_state);
         }
     }
 }
diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 8054bc4147..91c7fdaab1 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -1877,7 +1877,7 @@ static void pc_machine_reset(MachineState *machine)
         cpu = X86_CPU(cs);
 
         if (cpu->apic_state) {
-            device_reset(cpu->apic_state);
+            device_legacy_reset(cpu->apic_state);
         }
     }
 }
diff --git a/hw/ide/microdrive.c b/hw/ide/microdrive.c
index b0272ea14b..6b30e36ed8 100644
--- a/hw/ide/microdrive.c
+++ b/hw/ide/microdrive.c
@@ -173,7 +173,7 @@ static void md_attr_write(PCMCIACardState *card, uint32_t at, uint8_t value)
     case 0x00:	/* Configuration Option Register */
         s->opt = value & 0xcf;
         if (value & OPT_SRESET) {
-            device_reset(DEVICE(s));
+            device_legacy_reset(DEVICE(s));
         }
         md_interrupt_update(s);
         break;
@@ -316,7 +316,7 @@ static void md_common_write(PCMCIACardState *card, uint32_t at, uint16_t value)
     case 0xe:	/* Device Control */
         s->ctrl = value;
         if (value & CTRL_SRST) {
-            device_reset(DEVICE(s));
+            device_legacy_reset(DEVICE(s));
         }
         md_interrupt_update(s);
         break;
@@ -541,7 +541,7 @@ static int dscm1xxxx_attach(PCMCIACardState *card)
     md->attr_base = pcc->cis[0x74] | (pcc->cis[0x76] << 8);
     md->io_base = 0x0;
 
-    device_reset(DEVICE(md));
+    device_legacy_reset(DEVICE(md));
     md_interrupt_update(md);
 
     return 0;
@@ -551,7 +551,7 @@ static int dscm1xxxx_detach(PCMCIACardState *card)
 {
     MicroDriveState *md = MICRODRIVE(card);
 
-    device_reset(DEVICE(md));
+    device_legacy_reset(DEVICE(md));
     return 0;
 }
 
diff --git a/hw/intc/spapr_xive.c b/hw/intc/spapr_xive.c
index 7663123878..52bab29784 100644
--- a/hw/intc/spapr_xive.c
+++ b/hw/intc/spapr_xive.c
@@ -1766,7 +1766,7 @@ static target_ulong h_int_reset(PowerPCCPU *cpu,
         return H_PARAMETER;
     }
 
-    device_reset(DEVICE(xive));
+    device_legacy_reset(DEVICE(xive));
 
     if (kvm_irqchip_in_kernel()) {
         Error *local_err = NULL;
diff --git a/hw/ppc/pnv_psi.c b/hw/ppc/pnv_psi.c
index 1d8da31738..916e2a9ba7 100644
--- a/hw/ppc/pnv_psi.c
+++ b/hw/ppc/pnv_psi.c
@@ -466,7 +466,7 @@ static void pnv_psi_reset(DeviceState *dev)
 
 static void pnv_psi_reset_handler(void *dev)
 {
-    device_reset(DEVICE(dev));
+    device_legacy_reset(DEVICE(dev));
 }
 
 static void pnv_psi_realize(DeviceState *dev, Error **errp)
@@ -715,7 +715,7 @@ static void pnv_psi_p9_mmio_write(void *opaque, hwaddr addr,
         break;
     case PSIHB9_INTERRUPT_CONTROL:
         if (val & PSIHB9_IRQ_RESET) {
-            device_reset(DEVICE(&psi9->source));
+            device_legacy_reset(DEVICE(&psi9->source));
         }
         psi->regs[reg] = val;
         break;
diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
index 723373de73..81b5d1b6f2 100644
--- a/hw/ppc/spapr_pci.c
+++ b/hw/ppc/spapr_pci.c
@@ -2014,7 +2014,7 @@ static int spapr_phb_children_reset(Object *child, void *opaque)
     DeviceState *dev = (DeviceState *) object_dynamic_cast(child, TYPE_DEVICE);
 
     if (dev) {
-        device_reset(dev);
+        device_legacy_reset(dev);
     }
 
     return 0;
diff --git a/hw/ppc/spapr_vio.c b/hw/ppc/spapr_vio.c
index 554de9930d..f14944e900 100644
--- a/hw/ppc/spapr_vio.c
+++ b/hw/ppc/spapr_vio.c
@@ -304,7 +304,7 @@ int spapr_vio_send_crq(SpaprVioDevice *dev, uint8_t *crq)
 static void spapr_vio_quiesce_one(SpaprVioDevice *dev)
 {
     if (dev->tcet) {
-        device_reset(DEVICE(dev->tcet));
+        device_legacy_reset(DEVICE(dev->tcet));
     }
     free_crq(dev);
 }
diff --git a/hw/s390x/s390-pci-inst.c b/hw/s390x/s390-pci-inst.c
index 92c7e45df5..2f7a7d7bd1 100644
--- a/hw/s390x/s390-pci-inst.c
+++ b/hw/s390x/s390-pci-inst.c
@@ -243,7 +243,7 @@ int clp_service_call(S390CPU *cpu, uint8_t r2, uintptr_t ra)
                 stw_p(&ressetpci->hdr.rsp, CLP_RC_SETPCIFN_FHOP);
                 goto out;
             }
-            device_reset(DEVICE(pbdev));
+            device_legacy_reset(DEVICE(pbdev));
             pbdev->fh &= ~FH_MASK_ENABLE;
             pbdev->state = ZPCI_FS_DISABLED;
             stl_p(&ressetpci->fh, pbdev->fh);
diff --git a/hw/scsi/vmw_pvscsi.c b/hw/scsi/vmw_pvscsi.c
index 452a3b63b2..7baab1532f 100644
--- a/hw/scsi/vmw_pvscsi.c
+++ b/hw/scsi/vmw_pvscsi.c
@@ -838,7 +838,7 @@ pvscsi_on_cmd_reset_device(PVSCSIState *s)
 
     if (sdev != NULL) {
         s->resetting++;
-        device_reset(&sdev->qdev);
+        device_legacy_reset(&sdev->qdev);
         s->resetting--;
         return PVSCSI_COMMAND_PROCESSING_SUCCEEDED;
     }
diff --git a/hw/sd/omap_mmc.c b/hw/sd/omap_mmc.c
index c6e516b611..4088a8a80b 100644
--- a/hw/sd/omap_mmc.c
+++ b/hw/sd/omap_mmc.c
@@ -318,7 +318,7 @@ void omap_mmc_reset(struct omap_mmc_s *host)
      * into any bus, and we must reset it manually. When omap_mmc is
      * QOMified this must move into the QOM reset function.
      */
-    device_reset(DEVICE(host->card));
+    device_legacy_reset(DEVICE(host->card));
 }
 
 static uint64_t omap_mmc_read(void *opaque, hwaddr offset,
diff --git a/hw/sd/pl181.c b/hw/sd/pl181.c
index 8033fe455d..2b3776a6a0 100644
--- a/hw/sd/pl181.c
+++ b/hw/sd/pl181.c
@@ -482,7 +482,7 @@ static void pl181_reset(DeviceState *d)
     /* Since we're still using the legacy SD API the card is not plugged
      * into any bus, and we must reset it manually.
      */
-    device_reset(DEVICE(s->card));
+    device_legacy_reset(DEVICE(s->card));
 }
 
 static void pl181_init(Object *obj)
-- 
2.24.1

[PATCH v7 02/11] hw/core/qdev: add trace events to help with resettable transition

[Damien Hedde]

Adds trace events to reset procedure and when updating the parent
bus of a device.

Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
---
 hw/core/qdev.c       | 29 ++++++++++++++++++++++++++---
 hw/core/trace-events |  9 +++++++++
 2 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index 8c0c8284c8..5cb03136b5 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -38,6 +38,7 @@
 #include "hw/boards.h"
 #include "hw/sysbus.h"
 #include "migration/vmstate.h"
+#include "trace.h"
 
 bool qdev_hotplug = false;
 static bool qdev_hot_added = false;
@@ -98,7 +99,11 @@ void qdev_set_parent_bus(DeviceState *dev, BusState *bus)
     bool replugging = dev->parent_bus != NULL;
 
     if (replugging) {
-        /* Keep a reference to the device while it's not plugged into
+        trace_qdev_update_parent_bus(dev, object_get_typename(OBJECT(dev)),
+            dev->parent_bus, object_get_typename(OBJECT(dev->parent_bus)),
+            OBJECT(bus), object_get_typename(OBJECT(bus)));
+        /*
+         * Keep a reference to the device while it's not plugged into
          * any bus, to avoid it potentially evaporating when it is
          * dereffed in bus_remove_child().
          */
@@ -296,6 +301,18 @@ HotplugHandler *qdev_get_hotplug_handler(DeviceState *dev)
     return hotplug_ctrl;
 }
 
+static int qdev_prereset(DeviceState *dev, void *opaque)
+{
+    trace_qdev_reset_tree(dev, object_get_typename(OBJECT(dev)));
+    return 0;
+}
+
+static int qbus_prereset(BusState *bus, void *opaque)
+{
+    trace_qbus_reset_tree(bus, object_get_typename(OBJECT(bus)));
+    return 0;
+}
+
 static int qdev_reset_one(DeviceState *dev, void *opaque)
 {
     device_legacy_reset(dev);
@@ -306,6 +323,7 @@ static int qdev_reset_one(DeviceState *dev, void *opaque)
 static int qbus_reset_one(BusState *bus, void *opaque)
 {
     BusClass *bc = BUS_GET_CLASS(bus);
+    trace_qbus_reset(bus, object_get_typename(OBJECT(bus)));
     if (bc->reset) {
         bc->reset(bus);
     }
@@ -314,7 +332,9 @@ static int qbus_reset_one(BusState *bus, void *opaque)
 
 void qdev_reset_all(DeviceState *dev)
 {
-    qdev_walk_children(dev, NULL, NULL, qdev_reset_one, qbus_reset_one, NULL);
+    trace_qdev_reset_all(dev, object_get_typename(OBJECT(dev)));
+    qdev_walk_children(dev, qdev_prereset, qbus_prereset,
+                       qdev_reset_one, qbus_reset_one, NULL);
 }
 
 void qdev_reset_all_fn(void *opaque)
@@ -324,7 +344,9 @@ void qdev_reset_all_fn(void *opaque)
 
 void qbus_reset_all(BusState *bus)
 {
-    qbus_walk_children(bus, NULL, NULL, qdev_reset_one, qbus_reset_one, NULL);
+    trace_qbus_reset_all(bus, object_get_typename(OBJECT(bus)));
+    qbus_walk_children(bus, qdev_prereset, qbus_prereset,
+                       qdev_reset_one, qbus_reset_one, NULL);
 }
 
 void qbus_reset_all_fn(void *opaque)
@@ -1131,6 +1153,7 @@ void device_legacy_reset(DeviceState *dev)
 {
     DeviceClass *klass = DEVICE_GET_CLASS(dev);
 
+    trace_qdev_reset(dev, object_get_typename(OBJECT(dev)));
     if (klass->reset) {
         klass->reset(dev);
     }
diff --git a/hw/core/trace-events b/hw/core/trace-events
index fe47a9c8cb..a375aa88a4 100644
--- a/hw/core/trace-events
+++ b/hw/core/trace-events
@@ -1,2 +1,11 @@
 # loader.c
 loader_write_rom(const char *name, uint64_t gpa, uint64_t size, bool isrom) "%s: @0x%"PRIx64" size=0x%"PRIx64" ROM=%d"
+
+# qdev.c
+qdev_reset(void *obj, const char *objtype) "obj=%p(%s)"
+qdev_reset_all(void *obj, const char *objtype) "obj=%p(%s)"
+qdev_reset_tree(void *obj, const char *objtype) "obj=%p(%s)"
+qbus_reset(void *obj, const char *objtype) "obj=%p(%s)"
+qbus_reset_all(void *obj, const char *objtype) "obj=%p(%s)"
+qbus_reset_tree(void *obj, const char *objtype) "obj=%p(%s)"
+qdev_update_parent_bus(void *obj, const char *objtype, void *oldp, const char *oldptype, void *newp, const char *newptype) "obj=%p(%s) old_parent=%p(%s) new_parent=%p(%s)"
-- 
2.24.1

[PATCH v7 03/11] hw/core: create Resettable QOM interface

[Damien Hedde]

This commit defines an interface allowing multi-phase reset. This aims
to solve a problem of the actual single-phase reset (built in
DeviceClass and BusClass): reset behavior is dependent on the order
in which reset handlers are called. In particular doing external
side-effect (like setting an qemu_irq) is problematic because receiving
object may not be reset yet.

The Resettable interface divides the reset in 3 well defined phases.
To reset an object tree, all 1st phases are executed then all 2nd then
all 3rd. See the comments in include/hw/resettable.h for a more complete
description. The interface defines 3 phases to let the future
possibility of holding an object into reset for some time.

The qdev/qbus reset in DeviceClass and BusClass will be modified in
following commits to use this interface. A mechanism is provided
to allow executing a transitional reset handler in place of the 2nd
phase which is executed in children-then-parent order inside a tree.
This will allow to transition devices and buses smoothly while
keeping the exact current qdev/qbus reset behavior for now.

Documentation will be added in a following commit.

Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
---

v7 update: un-nest struct ResettablePhases
---
 Makefile.objs           |   1 +
 include/hw/resettable.h | 211 +++++++++++++++++++++++++++++++++++
 hw/core/resettable.c    | 238 ++++++++++++++++++++++++++++++++++++++++
 hw/core/Makefile.objs   |   1 +
 hw/core/trace-events    |  17 +++
 5 files changed, 468 insertions(+)
 create mode 100644 include/hw/resettable.h
 create mode 100644 hw/core/resettable.c

diff --git a/Makefile.objs b/Makefile.objs
index 7c1e50f9d6..9752d549b4 100644
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -191,6 +191,7 @@ trace-events-subdirs += migration
 trace-events-subdirs += net
 trace-events-subdirs += ui
 endif
+trace-events-subdirs += hw/core
 trace-events-subdirs += hw/display
 trace-events-subdirs += qapi
 trace-events-subdirs += qom
diff --git a/include/hw/resettable.h b/include/hw/resettable.h
new file mode 100644
index 0000000000..58b3df4c22
--- /dev/null
+++ b/include/hw/resettable.h
@@ -0,0 +1,211 @@
+/*
+ * Resettable interface header.
+ *
+ * Copyright (c) 2019 GreenSocs SAS
+ *
+ * Authors:
+ *   Damien Hedde
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef HW_RESETTABLE_H
+#define HW_RESETTABLE_H
+
+#include "qom/object.h"
+
+#define TYPE_RESETTABLE_INTERFACE "resettable"
+
+#define RESETTABLE_CLASS(class) \
+    OBJECT_CLASS_CHECK(ResettableClass, (class), TYPE_RESETTABLE_INTERFACE)
+
+#define RESETTABLE_GET_CLASS(obj) \
+    OBJECT_GET_CLASS(ResettableClass, (obj), TYPE_RESETTABLE_INTERFACE)
+
+typedef struct ResettableState ResettableState;
+
+/**
+ * ResetType:
+ * Types of reset.
+ *
+ * + Cold: reset resulting from a power cycle of the object.
+ *
+ * TODO: Support has to be added to handle more types. In particular,
+ * ResettableState structure needs to be expanded.
+ */
+typedef enum ResetType {
+    RESET_TYPE_COLD,
+} ResetType;
+
+/*
+ * ResettableClass:
+ * Interface for resettable objects.
+ *
+ * See docs/devel/reset.rst for more detailed information about how QEMU models
+ * reset. This whole API must only be used when holding the iothread mutex.
+ *
+ * All objects which can be reset must implement this interface;
+ * it is usually provided by a base class such as DeviceClass or BusClass.
+ * Every Resettable object must maintain some state tracking the
+ * progress of a reset operation by providing a ResettableState structure.
+ * The functions defined in this module take care of updating the
+ * state of the reset.
+ * The base class implementation of the interface provides this
+ * state and implements the associated method: get_state.
+ *
+ * Concrete object implementations (typically specific devices
+ * such as a UART model) should provide the functions
+ * for the phases.enter, phases.hold and phases.exit methods, which
+ * they can set in their class init function, either directly or
+ * by calling resettable_class_set_parent_phases().
+ * The phase methods are guaranteed to only only ever be called once
+ * for any reset event, in the order 'enter', 'hold', 'exit'.
+ * An object will always move quickly from 'enter' to 'hold'
+ * but might remain in 'hold' for an arbitrary period of time
+ * before eventually reset is deasserted and the 'exit' phase is called.
+ * Object implementations should be prepared for functions handling
+ * inbound connections from other devices (such as qemu_irq handler
+ * functions) to be called at any point during reset after their
+ * 'enter' method has been called.
+ *
+ * Users of a resettable object should not call these methods
+ * directly, but instead use the function resettable_reset().
+ *
+ * @phases.enter: This phase is called when the object enters reset. It
+ * should reset local state of the object, but it must not do anything that
+ * has a side-effect on other objects, such as raising or lowering a qemu_irq
+ * line or reading or writing guest memory. It takes the reset's type as
+ * argument.
+ *
+ * @phases.hold: This phase is called for entry into reset, once every object
+ * in the system which is being reset has had its @phases.enter method called.
+ * At this point devices can do actions that affect other objects.
+ *
+ * @phases.exit: This phase is called when the object leaves the reset state.
+ * Actions affecting other objects are permitted.
+ *
+ * @get_state: Mandatory method which must return a pointer to a
+ * ResettableState.
+ *
+ * @get_transitional_function: transitional method to handle Resettable objects
+ * not yet fully moved to this interface. It will be removed as soon as it is
+ * not needed anymore. This method is optional and may return a pointer to a
+ * function to be used instead of the phases. If the method exists and returns
+ * a non-NULL function pointer then that function is executed as a replacement
+ * of the 'hold' phase method taking the object as argument. The two other phase
+ * methods are not executed.
+ *
+ * @child_foreach: Executes a given callback on every Resettable child. Child
+ * in this context means a child in the qbus tree, so the children of a qbus
+ * are the devices on it, and the children of a device are all the buses it
+ * owns. This is not the same as the QOM object hierarchy. The function takes
+ * additional opaque and ResetType arguments which must be passed unmodified to
+ * the callback.
+ */
+typedef void (*ResettableEnterPhase)(Object *obj, ResetType type);
+typedef void (*ResettableHoldPhase)(Object *obj);
+typedef void (*ResettableExitPhase)(Object *obj);
+typedef ResettableState * (*ResettableGetState)(Object *obj);
+typedef void (*ResettableTrFunction)(Object *obj);
+typedef ResettableTrFunction (*ResettableGetTrFunction)(Object *obj);
+typedef void (*ResettableChildCallback)(Object *, void *opaque,
+                                        ResetType type);
+typedef void (*ResettableChildForeach)(Object *obj,
+                                       ResettableChildCallback cb,
+                                       void *opaque, ResetType type);
+typedef struct ResettablePhases {
+    ResettableEnterPhase enter;
+    ResettableHoldPhase hold;
+    ResettableExitPhase exit;
+} ResettablePhases;
+typedef struct ResettableClass {
+    InterfaceClass parent_class;
+
+    /* Phase methods */
+    ResettablePhases phases;
+
+    /* State access method */
+    ResettableGetState get_state;
+
+    /* Transitional method for legacy reset compatibility */
+    ResettableGetTrFunction get_transitional_function;
+
+    /* Hierarchy handling method */
+    ResettableChildForeach child_foreach;
+} ResettableClass;
+
+/**
+ * ResettableState:
+ * Structure holding reset related state. The fields should not be accessed
+ * directly; the definition is here to allow further inclusion into other
+ * objects.
+ *
+ * @count: Number of reset level the object is into. It is incremented when
+ * the reset operation starts and decremented when it finishes.
+ * @hold_phase_pending: flag which indicates that we need to invoke the 'hold'
+ * phase handler for this object.
+ * @exit_phase_in_progress: true if we are currently in the exit phase
+ */
+struct ResettableState {
+    uint32_t count;
+    bool hold_phase_pending;
+    bool exit_phase_in_progress;
+};
+
+/**
+ * resettable_reset:
+ * Trigger a reset on an object @obj of type @type. @obj must implement
+ * Resettable interface.
+ *
+ * Calling this function is equivalent to calling @resettable_assert_reset()
+ * then @resettable_release_reset().
+ */
+void resettable_reset(Object *obj, ResetType type);
+
+/**
+ * resettable_assert_reset:
+ * Put an object @obj into reset. @obj must implement Resettable interface.
+ *
+ * @resettable_release_reset() must eventually be called after this call.
+ * There must be one call to @resettable_release_reset() per call of
+ * @resettable_assert_reset(), with the same type argument.
+ *
+ * NOTE: Until support for migration is added, the @resettable_release_reset()
+ * must not be delayed. It must occur just after @resettable_assert_reset() so
+ * that migration cannot be triggered in between. Prefer using
+ * @resettable_reset() for now.
+ */
+void resettable_assert_reset(Object *obj, ResetType type);
+
+/**
+ * resettable_release_reset:
+ * Release the object @obj from reset. @obj must implement Resettable interface.
+ *
+ * See @resettable_assert_reset() description for details.
+ */
+void resettable_release_reset(Object *obj, ResetType type);
+
+/**
+ * resettable_is_in_reset:
+ * Return true if @obj is under reset.
+ *
+ * @obj must implement Resettable interface.
+ */
+bool resettable_is_in_reset(Object *obj);
+
+/**
+ * resettable_class_set_parent_phases:
+ *
+ * Save @rc current reset phases into @parent_phases and override @rc phases
+ * by the given new methods (@enter, @hold and @exit).
+ * Each phase is overridden only if the new one is not NULL allowing to
+ * override a subset of phases.
+ */
+void resettable_class_set_parent_phases(ResettableClass *rc,
+                                        ResettableEnterPhase enter,
+                                        ResettableHoldPhase hold,
+                                        ResettableExitPhase exit,
+                                        ResettablePhases *parent_phases);
+
+#endif
diff --git a/hw/core/resettable.c b/hw/core/resettable.c
new file mode 100644
index 0000000000..9133208487
--- /dev/null
+++ b/hw/core/resettable.c
@@ -0,0 +1,238 @@
+/*
+ * Resettable interface.
+ *
+ * Copyright (c) 2019 GreenSocs SAS
+ *
+ * Authors:
+ *   Damien Hedde
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/module.h"
+#include "hw/resettable.h"
+#include "trace.h"
+
+/**
+ * resettable_phase_enter/hold/exit:
+ * Function executing a phase recursively in a resettable object and its
+ * children.
+ */
+static void resettable_phase_enter(Object *obj, void *opaque, ResetType type);
+static void resettable_phase_hold(Object *obj, void *opaque, ResetType type);
+static void resettable_phase_exit(Object *obj, void *opaque, ResetType type);
+
+/**
+ * enter_phase_in_progress:
+ * True if we are currently in reset enter phase.
+ *
+ * Note: This flag is only used to guarantee (using asserts) that the reset
+ * API is used correctly. We can use a global variable because we rely on the
+ * iothread mutex to ensure only one reset operation is in a progress at a
+ * given time.
+ */
+static bool enter_phase_in_progress;
+
+void resettable_reset(Object *obj, ResetType type)
+{
+    trace_resettable_reset(obj, type);
+    resettable_assert_reset(obj, type);
+    resettable_release_reset(obj, type);
+}
+
+void resettable_assert_reset(Object *obj, ResetType type)
+{
+    /* TODO: change this assert when adding support for other reset types */
+    assert(type == RESET_TYPE_COLD);
+    trace_resettable_reset_assert_begin(obj, type);
+    assert(!enter_phase_in_progress);
+
+    enter_phase_in_progress = true;
+    resettable_phase_enter(obj, NULL, type);
+    enter_phase_in_progress = false;
+
+    resettable_phase_hold(obj, NULL, type);
+
+    trace_resettable_reset_assert_end(obj);
+}
+
+void resettable_release_reset(Object *obj, ResetType type)
+{
+    /* TODO: change this assert when adding support for other reset types */
+    assert(type == RESET_TYPE_COLD);
+    trace_resettable_reset_release_begin(obj, type);
+    assert(!enter_phase_in_progress);
+
+    resettable_phase_exit(obj, NULL, type);
+
+    trace_resettable_reset_release_end(obj);
+}
+
+bool resettable_is_in_reset(Object *obj)
+{
+    ResettableClass *rc = RESETTABLE_GET_CLASS(obj);
+    ResettableState *s = rc->get_state(obj);
+
+    return s->count > 0;
+}
+
+/**
+ * resettable_child_foreach:
+ * helper to avoid checking the existence of the method.
+ */
+static void resettable_child_foreach(ResettableClass *rc, Object *obj,
+                                     ResettableChildCallback cb,
+                                     void *opaque, ResetType type)
+{
+    if (rc->child_foreach) {
+        rc->child_foreach(obj, cb, opaque, type);
+    }
+}
+
+/**
+ * resettable_get_tr_func:
+ * helper to fetch transitional reset callback if any.
+ */
+static ResettableTrFunction resettable_get_tr_func(ResettableClass *rc,
+                                                   Object *obj)
+{
+    ResettableTrFunction tr_func = NULL;
+    if (rc->get_transitional_function) {
+        tr_func = rc->get_transitional_function(obj);
+    }
+    return tr_func;
+}
+
+static void resettable_phase_enter(Object *obj, void *opaque, ResetType type)
+{
+    ResettableClass *rc = RESETTABLE_GET_CLASS(obj);
+    ResettableState *s = rc->get_state(obj);
+    const char *obj_typename = object_get_typename(obj);
+    bool action_needed = false;
+
+    /* exit phase has to finish properly before entering back in reset */
+    assert(!s->exit_phase_in_progress);
+
+    trace_resettable_phase_enter_begin(obj, obj_typename, s->count, type);
+
+    /* Only take action if we really enter reset for the 1st time. */
+    /*
+     * TODO: if adding more ResetType support, some additional checks
+     * are probably needed here.
+     */
+    if (s->count++ == 0) {
+        action_needed = true;
+    }
+    /*
+     * We limit the count to an arbitrary "big" value. The value is big
+     * enough not to be triggered normally.
+     * The assert will stop an infinite loop if there is a cycle in the
+     * reset tree. The loop goes through resettable_foreach_child below
+     * which at some point will call us again.
+     */
+    assert(s->count <= 50);
+
+    /*
+     * handle the children even if action_needed is at false so that
+     * child counts are incremented too
+     */
+    resettable_child_foreach(rc, obj, resettable_phase_enter, NULL, type);
+
+    /* execute enter phase for the object if needed */
+    if (action_needed) {
+        trace_resettable_phase_enter_exec(obj, obj_typename, type,
+                                          !!rc->phases.enter);
+        if (rc->phases.enter && !resettable_get_tr_func(rc, obj)) {
+            rc->phases.enter(obj, type);
+        }
+        s->hold_phase_pending = true;
+    }
+    trace_resettable_phase_enter_end(obj, obj_typename, s->count);
+}
+
+static void resettable_phase_hold(Object *obj, void *opaque, ResetType type)
+{
+    ResettableClass *rc = RESETTABLE_GET_CLASS(obj);
+    ResettableState *s = rc->get_state(obj);
+    const char *obj_typename = object_get_typename(obj);
+
+    /* exit phase has to finish properly before entering back in reset */
+    assert(!s->exit_phase_in_progress);
+
+    trace_resettable_phase_hold_begin(obj, obj_typename, s->count, type);
+
+    /* handle children first */
+    resettable_child_foreach(rc, obj, resettable_phase_hold, NULL, type);
+
+    /* exec hold phase */
+    if (s->hold_phase_pending) {
+        s->hold_phase_pending = false;
+        ResettableTrFunction tr_func = resettable_get_tr_func(rc, obj);
+        trace_resettable_phase_hold_exec(obj, obj_typename, !!rc->phases.hold);
+        if (tr_func) {
+            trace_resettable_transitional_function(obj, obj_typename);
+            tr_func(obj);
+        } else if (rc->phases.hold) {
+            rc->phases.hold(obj);
+        }
+    }
+    trace_resettable_phase_hold_end(obj, obj_typename, s->count);
+}
+
+static void resettable_phase_exit(Object *obj, void *opaque, ResetType type)
+{
+    ResettableClass *rc = RESETTABLE_GET_CLASS(obj);
+    ResettableState *s = rc->get_state(obj);
+    const char *obj_typename = object_get_typename(obj);
+
+    assert(!s->exit_phase_in_progress);
+    trace_resettable_phase_exit_begin(obj, obj_typename, s->count, type);
+
+    /* exit_phase_in_progress ensures this phase is 'atomic' */
+    s->exit_phase_in_progress = true;
+    resettable_child_foreach(rc, obj, resettable_phase_exit, NULL, type);
+
+    assert(s->count > 0);
+    if (s->count == 1) {
+        trace_resettable_phase_exit_exec(obj, obj_typename, !!rc->phases.exit);
+        if (rc->phases.exit && !resettable_get_tr_func(rc, obj)) {
+            rc->phases.exit(obj);
+        }
+        s->count = 0;
+    }
+    s->exit_phase_in_progress = false;
+    trace_resettable_phase_exit_end(obj, obj_typename, s->count);
+}
+
+void resettable_class_set_parent_phases(ResettableClass *rc,
+                                        ResettableEnterPhase enter,
+                                        ResettableHoldPhase hold,
+                                        ResettableExitPhase exit,
+                                        ResettablePhases *parent_phases)
+{
+    *parent_phases = rc->phases;
+    if (enter) {
+        rc->phases.enter = enter;
+    }
+    if (hold) {
+        rc->phases.hold = hold;
+    }
+    if (exit) {
+        rc->phases.exit = exit;
+    }
+}
+
+static const TypeInfo resettable_interface_info = {
+    .name       = TYPE_RESETTABLE_INTERFACE,
+    .parent     = TYPE_INTERFACE,
+    .class_size = sizeof(ResettableClass),
+};
+
+static void reset_register_types(void)
+{
+    type_register_static(&resettable_interface_info);
+}
+
+type_init(reset_register_types)
diff --git a/hw/core/Makefile.objs b/hw/core/Makefile.objs
index 0edd9e635d..1709a122d4 100644
--- a/hw/core/Makefile.objs
+++ b/hw/core/Makefile.objs
@@ -1,6 +1,7 @@
 # core qdev-related obj files, also used by *-user:
 common-obj-y += qdev.o qdev-properties.o
 common-obj-y += bus.o reset.o
+common-obj-y += resettable.o
 common-obj-$(CONFIG_SOFTMMU) += qdev-fw.o
 common-obj-$(CONFIG_SOFTMMU) += fw-path-provider.o
 # irq.o needed for qdev GPIO handling:
diff --git a/hw/core/trace-events b/hw/core/trace-events
index a375aa88a4..a2e43f1120 100644
--- a/hw/core/trace-events
+++ b/hw/core/trace-events
@@ -9,3 +9,20 @@ qbus_reset(void *obj, const char *objtype) "obj=%p(%s)"
 qbus_reset_all(void *obj, const char *objtype) "obj=%p(%s)"
 qbus_reset_tree(void *obj, const char *objtype) "obj=%p(%s)"
 qdev_update_parent_bus(void *obj, const char *objtype, void *oldp, const char *oldptype, void *newp, const char *newptype) "obj=%p(%s) old_parent=%p(%s) new_parent=%p(%s)"
+
+# resettable.c
+resettable_reset(void *obj, int cold) "obj=%p cold=%d"
+resettable_reset_assert_begin(void *obj, int cold) "obj=%p cold=%d"
+resettable_reset_assert_end(void *obj) "obj=%p"
+resettable_reset_release_begin(void *obj, int cold) "obj=%p cold=%d"
+resettable_reset_release_end(void *obj) "obj=%p"
+resettable_phase_enter_begin(void *obj, const char *objtype, uint32_t count, int type) "obj=%p(%s) count=%" PRIu32 " type=%d"
+resettable_phase_enter_exec(void *obj, const char *objtype, int type, int has_method) "obj=%p(%s) type=%d method=%d"
+resettable_phase_enter_end(void *obj, const char *objtype, uint32_t count) "obj=%p(%s) count=%" PRIu32
+resettable_phase_hold_begin(void *obj, const char *objtype, uint32_t count, int type) "obj=%p(%s) count=%" PRIu32 " type=%d"
+resettable_phase_hold_exec(void *obj, const char *objtype, int has_method) "obj=%p(%s) method=%d"
+resettable_phase_hold_end(void *obj, const char *objtype, uint32_t count) "obj=%p(%s) count=%" PRIu32
+resettable_phase_exit_begin(void *obj, const char *objtype, uint32_t count, int type) "obj=%p(%s) count=%" PRIu32 " type=%d"
+resettable_phase_exit_exec(void *obj, const char *objtype, int has_method) "obj=%p(%s) method=%d"
+resettable_phase_exit_end(void *obj, const char *objtype, uint32_t count) "obj=%p(%s) count=%" PRIu32
+resettable_transitional_function(void *obj, const char *objtype) "obj=%p(%s)"
-- 
2.24.1

[PATCH v7 04/11] hw/core: add Resettable support to BusClass and DeviceClass

[Damien Hedde]

This commit adds support of Resettable interface to buses and devices:
+ ResettableState structure is added in the Bus/Device state
+ Resettable methods are implemented.
+ device/bus_is_in_reset function defined

This commit allows to transition the objects to the new
multi-phase interface without changing the reset behavior at all.
Object single reset method can be split into the 3 different phases
but the 3 phases are still executed in a row for a given object.
From the qdev/qbus reset api point of view, nothing is changed.
qdev_reset_all() and qbus_reset_all() are not modified as well as
device_legacy_reset().

Transition of an object must be done from parent class to child class.
Care has been taken to allow the transition of a parent class
without requiring the child classes to be transitioned at the same
time. Note that SysBus and SysBusDevice class do not need any transition
because they do not override the legacy reset method.

Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
---
 include/hw/qdev-core.h | 27 ++++++++++++
 hw/core/bus.c          | 97 ++++++++++++++++++++++++++++++++++++++++++
 hw/core/qdev.c         | 93 ++++++++++++++++++++++++++++++++++++++++
 tests/Makefile.include |  1 +
 4 files changed, 218 insertions(+)

diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
index b8341b0fb0..1b4b420617 100644
--- a/include/hw/qdev-core.h
+++ b/include/hw/qdev-core.h
@@ -5,6 +5,7 @@
 #include "qemu/bitmap.h"
 #include "qom/object.h"
 #include "hw/hotplug.h"
+#include "hw/resettable.h"
 
 enum {
     DEV_NVECTORS_UNSPECIFIED = -1,
@@ -117,6 +118,11 @@ typedef struct DeviceClass {
     bool hotpluggable;
 
     /* callbacks */
+    /*
+     * Reset method here is deprecated and replaced by methods in the
+     * resettable class interface to implement a multi-phase reset.
+     * TODO: remove once every reset callback is unused
+     */
     DeviceReset reset;
     DeviceRealize realize;
     DeviceUnrealize unrealize;
@@ -141,6 +147,7 @@ struct NamedGPIOList {
 /**
  * DeviceState:
  * @realized: Indicates whether the device has been fully constructed.
+ * @reset: ResettableState for the device; handled by Resettable interface.
  *
  * This structure should not be accessed directly.  We declare it here
  * so that it can be embedded in individual device state structures.
@@ -163,6 +170,7 @@ struct DeviceState {
     int num_child_bus;
     int instance_id_alias;
     int alias_required_for_version;
+    ResettableState reset;
 };
 
 struct DeviceListener {
@@ -215,6 +223,7 @@ typedef struct BusChild {
 /**
  * BusState:
  * @hotplug_handler: link to a hotplug handler associated with bus.
+ * @reset: ResettableState for the bus; handled by Resettable interface.
  */
 struct BusState {
     Object obj;
@@ -226,6 +235,7 @@ struct BusState {
     int num_children;
     QTAILQ_HEAD(, BusChild) children;
     QLIST_ENTRY(BusState) sibling;
+    ResettableState reset;
 };
 
 /**
@@ -412,6 +422,18 @@ void qdev_reset_all_fn(void *opaque);
 void qbus_reset_all(BusState *bus);
 void qbus_reset_all_fn(void *opaque);
 
+/**
+ * device_is_in_reset:
+ * Return true if the device @dev is currently being reset.
+ */
+bool device_is_in_reset(DeviceState *dev);
+
+/**
+ * bus_is_in_reset:
+ * Return true if the bus @bus is currently being reset.
+ */
+bool bus_is_in_reset(BusState *bus);
+
 /* This should go away once we get rid of the NULL bus hack */
 BusState *sysbus_get_default(void);
 
@@ -433,6 +455,11 @@ void qdev_machine_init(void);
  */
 void device_legacy_reset(DeviceState *dev);
 
+/**
+ * device_class_set_parent_reset:
+ * TODO: remove the function when DeviceClass's reset method
+ * is not used anymore.
+ */
 void device_class_set_parent_reset(DeviceClass *dc,
                                    DeviceReset dev_reset,
                                    DeviceReset *parent_reset);
diff --git a/hw/core/bus.c b/hw/core/bus.c
index 7f3d2a3dbd..2698f715bd 100644
--- a/hw/core/bus.c
+++ b/hw/core/bus.c
@@ -68,6 +68,28 @@ int qbus_walk_children(BusState *bus,
     return 0;
 }
 
+bool bus_is_in_reset(BusState *bus)
+{
+    return resettable_is_in_reset(OBJECT(bus));
+}
+
+static ResettableState *bus_get_reset_state(Object *obj)
+{
+    BusState *bus = BUS(obj);
+    return &bus->reset;
+}
+
+static void bus_reset_child_foreach(Object *obj, ResettableChildCallback cb,
+                                    void *opaque, ResetType type)
+{
+    BusState *bus = BUS(obj);
+    BusChild *kid;
+
+    QTAILQ_FOREACH(kid, &bus->children, sibling) {
+        cb(OBJECT(kid->child), opaque, type);
+    }
+}
+
 static void qbus_realize(BusState *bus, DeviceState *parent, const char *name)
 {
     const char *typename = object_get_typename(OBJECT(bus));
@@ -199,12 +221,83 @@ static char *default_bus_get_fw_dev_path(DeviceState *dev)
     return g_strdup(object_get_typename(OBJECT(dev)));
 }
 
+/**
+ * bus_phases_reset:
+ * Transition reset method for buses to allow moving
+ * smoothly from legacy reset method to multi-phases
+ */
+static void bus_phases_reset(BusState *bus)
+{
+    ResettableClass *rc = RESETTABLE_GET_CLASS(bus);
+
+    if (rc->phases.enter) {
+        rc->phases.enter(OBJECT(bus), RESET_TYPE_COLD);
+    }
+    if (rc->phases.hold) {
+        rc->phases.hold(OBJECT(bus));
+    }
+    if (rc->phases.exit) {
+        rc->phases.exit(OBJECT(bus));
+    }
+}
+
+static void bus_transitional_reset(Object *obj)
+{
+    BusClass *bc = BUS_GET_CLASS(obj);
+
+    /*
+     * This will call either @bus_phases_reset (for multi-phases transitioned
+     * buses) or a bus's specific method for not-yet transitioned buses.
+     * In both case, it does not reset children.
+     */
+    if (bc->reset) {
+        bc->reset(BUS(obj));
+    }
+}
+
+/**
+ * bus_get_transitional_reset:
+ * check if the bus's class is ready for multi-phase
+ */
+static ResettableTrFunction bus_get_transitional_reset(Object *obj)
+{
+    BusClass *dc = BUS_GET_CLASS(obj);
+    if (dc->reset != bus_phases_reset) {
+        /*
+         * dc->reset has been overridden by a subclass,
+         * the bus is not ready for multi phase yet.
+         */
+        return bus_transitional_reset;
+    }
+    return NULL;
+}
+
 static void bus_class_init(ObjectClass *class, void *data)
 {
     BusClass *bc = BUS_CLASS(class);
+    ResettableClass *rc = RESETTABLE_CLASS(class);
 
     class->unparent = bus_unparent;
     bc->get_fw_dev_path = default_bus_get_fw_dev_path;
+
+    rc->get_state = bus_get_reset_state;
+    rc->child_foreach = bus_reset_child_foreach;
+
+    /*
+     * @bus_phases_reset is put as the default reset method below, allowing
+     * to do the multi-phase transition from base classes to leaf classes. It
+     * allows a legacy-reset Bus class to extend a multi-phases-reset
+     * Bus class for the following reason:
+     * + If a base class B has been moved to multi-phase, then it does not
+     *   override this default reset method and may have defined phase methods.
+     * + A child class C (extending class B) which uses
+     *   bus_class_set_parent_reset() (or similar means) to override the
+     *   reset method will still work as expected. @bus_phases_reset function
+     *   will be registered as the parent reset method and effectively call
+     *   parent reset phases.
+     */
+    bc->reset = bus_phases_reset;
+    rc->get_transitional_function = bus_get_transitional_reset;
 }
 
 static void qbus_finalize(Object *obj)
@@ -223,6 +316,10 @@ static const TypeInfo bus_info = {
     .instance_init = qbus_initfn,
     .instance_finalize = qbus_finalize,
     .class_init = bus_class_init,
+    .interfaces = (InterfaceInfo[]) {
+        { TYPE_RESETTABLE_INTERFACE },
+        { }
+    },
 };
 
 static void bus_register_types(void)
diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index 5cb03136b5..d431a020fc 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -355,6 +355,28 @@ void qbus_reset_all_fn(void *opaque)
     qbus_reset_all(bus);
 }
 
+bool device_is_in_reset(DeviceState *dev)
+{
+    return resettable_is_in_reset(OBJECT(dev));
+}
+
+static ResettableState *device_get_reset_state(Object *obj)
+{
+    DeviceState *dev = DEVICE(obj);
+    return &dev->reset;
+}
+
+static void device_reset_child_foreach(Object *obj, ResettableChildCallback cb,
+                                       void *opaque, ResetType type)
+{
+    DeviceState *dev = DEVICE(obj);
+    BusState *bus;
+
+    QLIST_FOREACH(bus, &dev->child_bus, sibling) {
+        cb(OBJECT(bus), opaque, type);
+    }
+}
+
 /* can be used as ->unplug() callback for the simple cases */
 void qdev_simple_device_unplug_cb(HotplugHandler *hotplug_dev,
                                   DeviceState *dev, Error **errp)
@@ -1107,10 +1129,62 @@ device_vmstate_if_get_id(VMStateIf *obj)
     return qdev_get_dev_path(dev);
 }
 
+/**
+ * device_phases_reset:
+ * Transition reset method for devices to allow moving
+ * smoothly from legacy reset method to multi-phases
+ */
+static void device_phases_reset(DeviceState *dev)
+{
+    ResettableClass *rc = RESETTABLE_GET_CLASS(dev);
+
+    if (rc->phases.enter) {
+        rc->phases.enter(OBJECT(dev), RESET_TYPE_COLD);
+    }
+    if (rc->phases.hold) {
+        rc->phases.hold(OBJECT(dev));
+    }
+    if (rc->phases.exit) {
+        rc->phases.exit(OBJECT(dev));
+    }
+}
+
+static void device_transitional_reset(Object *obj)
+{
+    DeviceClass *dc = DEVICE_GET_CLASS(obj);
+
+    /*
+     * This will call either @device_phases_reset (for multi-phases transitioned
+     * devices) or a device's specific method for not-yet transitioned devices.
+     * In both case, it does not reset children.
+     */
+    if (dc->reset) {
+        dc->reset(DEVICE(obj));
+    }
+}
+
+/**
+ * device_get_transitional_reset:
+ * check if the device's class is ready for multi-phase
+ */
+static ResettableTrFunction device_get_transitional_reset(Object *obj)
+{
+    DeviceClass *dc = DEVICE_GET_CLASS(obj);
+    if (dc->reset != device_phases_reset) {
+        /*
+         * dc->reset has been overridden by a subclass,
+         * the device is not ready for multi phase yet.
+         */
+        return device_transitional_reset;
+    }
+    return NULL;
+}
+
 static void device_class_init(ObjectClass *class, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(class);
     VMStateIfClass *vc = VMSTATE_IF_CLASS(class);
+    ResettableClass *rc = RESETTABLE_CLASS(class);
 
     class->unparent = device_unparent;
 
@@ -1123,6 +1197,24 @@ static void device_class_init(ObjectClass *class, void *data)
     dc->hotpluggable = true;
     dc->user_creatable = true;
     vc->get_id = device_vmstate_if_get_id;
+    rc->get_state = device_get_reset_state;
+    rc->child_foreach = device_reset_child_foreach;
+
+    /*
+     * @device_phases_reset is put as the default reset method below, allowing
+     * to do the multi-phase transition from base classes to leaf classes. It
+     * allows a legacy-reset Device class to extend a multi-phases-reset
+     * Device class for the following reason:
+     * + If a base class B has been moved to multi-phase, then it does not
+     *   override this default reset method and may have defined phase methods.
+     * + A child class C (extending class B) which uses
+     *   device_class_set_parent_reset() (or similar means) to override the
+     *   reset method will still work as expected. @device_phases_reset function
+     *   will be registered as the parent reset method and effectively call
+     *   parent reset phases.
+     */
+    dc->reset = device_phases_reset;
+    rc->get_transitional_function = device_get_transitional_reset;
 }
 
 void device_class_set_parent_reset(DeviceClass *dc,
@@ -1183,6 +1275,7 @@ static const TypeInfo device_type_info = {
     .class_size = sizeof(DeviceClass),
     .interfaces = (InterfaceInfo[]) {
         { TYPE_VMSTATE_IF },
+        { TYPE_RESETTABLE_INTERFACE },
         { }
     }
 };
diff --git a/tests/Makefile.include b/tests/Makefile.include
index 1ae14a8b15..8ad07621b0 100644
--- a/tests/Makefile.include
+++ b/tests/Makefile.include
@@ -427,6 +427,7 @@ tests/fp/%:
 tests/test-qdev-global-props$(EXESUF): tests/test-qdev-global-props.o \
 	hw/core/qdev.o hw/core/qdev-properties.o hw/core/hotplug.o\
 	hw/core/bus.o \
+	hw/core/resettable.o \
 	hw/core/irq.o \
 	hw/core/fw-path-provider.o \
 	hw/core/reset.o \
-- 
2.24.1

[PATCH v7 05/11] hw/core/resettable: add support for changing parent

[Damien Hedde]

Add a function resettable_change_parent() to do the required
plumbing when changing the parent a of Resettable object.

We need to make sure that the reset state of the object remains
coherent with the reset state of the new parent.

We make the 2 following hypothesis:
+ when an object is put in a parent under reset, the object goes in
reset.
+ when an object is removed from a parent under reset, the object
leaves reset.

The added function avoids any glitch if both old and new parent are
already in reset.

Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
---
 include/hw/resettable.h | 16 +++++++++++
 hw/core/resettable.c    | 62 +++++++++++++++++++++++++++++++++++++++--
 hw/core/trace-events    |  1 +
 3 files changed, 77 insertions(+), 2 deletions(-)

diff --git a/include/hw/resettable.h b/include/hw/resettable.h
index 58b3df4c22..3c87ab86c7 100644
--- a/include/hw/resettable.h
+++ b/include/hw/resettable.h
@@ -194,6 +194,22 @@ void resettable_release_reset(Object *obj, ResetType type);
  */
 bool resettable_is_in_reset(Object *obj);
 
+/**
+ * resettable_change_parent:
+ * Indicate that the parent of Ressettable @obj is changing from @oldp to @newp.
+ * All 3 objects must implement resettable interface. @oldp or @newp may be
+ * NULL.
+ *
+ * This function will adapt the reset state of @obj so that it is coherent
+ * with the reset state of @newp. It may trigger @resettable_assert_reset()
+ * or @resettable_release_reset(). It will do such things only if the reset
+ * state of @newp and @oldp are different.
+ *
+ * When using this function during reset, it must only be called during
+ * a hold phase method. Calling this during enter or exit phase is an error.
+ */
+void resettable_change_parent(Object *obj, Object *newp, Object *oldp);
+
 /**
  * resettable_class_set_parent_phases:
  *
diff --git a/hw/core/resettable.c b/hw/core/resettable.c
index 9133208487..e99bb30058 100644
--- a/hw/core/resettable.c
+++ b/hw/core/resettable.c
@@ -28,12 +28,16 @@ static void resettable_phase_exit(Object *obj, void *opaque, ResetType type);
  * enter_phase_in_progress:
  * True if we are currently in reset enter phase.
  *
- * Note: This flag is only used to guarantee (using asserts) that the reset
- * API is used correctly. We can use a global variable because we rely on the
+ * exit_phase_in_progress:
+ * count the number of exit phase we are in.
+ *
+ * Note: These flags are only used to guarantee (using asserts) that the reset
+ * API is used correctly. We can use global variables because we rely on the
  * iothread mutex to ensure only one reset operation is in a progress at a
  * given time.
  */
 static bool enter_phase_in_progress;
+static unsigned exit_phase_in_progress;
 
 void resettable_reset(Object *obj, ResetType type)
 {
@@ -65,7 +69,9 @@ void resettable_release_reset(Object *obj, ResetType type)
     trace_resettable_reset_release_begin(obj, type);
     assert(!enter_phase_in_progress);
 
+    exit_phase_in_progress += 1;
     resettable_phase_exit(obj, NULL, type);
+    exit_phase_in_progress -= 1;
 
     trace_resettable_reset_release_end(obj);
 }
@@ -206,6 +212,58 @@ static void resettable_phase_exit(Object *obj, void *opaque, ResetType type)
     trace_resettable_phase_exit_end(obj, obj_typename, s->count);
 }
 
+/*
+ * resettable_get_count:
+ * Get the count of the Resettable object @obj. Return 0 if @obj is NULL.
+ */
+static uint32_t resettable_get_count(Object *obj)
+{
+    if (obj) {
+        ResettableClass *rc = RESETTABLE_GET_CLASS(obj);
+        return rc->get_state(obj)->count;
+    }
+    return 0;
+}
+
+void resettable_change_parent(Object *obj, Object *newp, Object *oldp)
+{
+    ResettableClass *rc = RESETTABLE_GET_CLASS(obj);
+    ResettableState *s = rc->get_state(obj);
+    uint32_t newp_count = resettable_get_count(newp);
+    uint32_t oldp_count = resettable_get_count(oldp);
+
+    /*
+     * Ensure we do not change parent when in enter or exit phase.
+     * During these phases, the reset subtree being updated is partly in reset
+     * and partly not in reset (it depends on the actual position in
+     * resettable_child_foreach()s). We are not able to tell in which part is a
+     * leaving or arriving device. Thus we cannot set the reset count of the
+     * moving device to the proper value.
+     */
+    assert(!enter_phase_in_progress && !exit_phase_in_progress);
+    trace_resettable_change_parent(obj, oldp, oldp_count, newp, newp_count);
+
+    /*
+     * At most one of the two 'for' loops will be executed below
+     * in order to cope with the difference between the two counts.
+     */
+    /* if newp is more reset than oldp */
+    for (uint32_t i = oldp_count; i < newp_count; i++) {
+        resettable_assert_reset(obj, RESET_TYPE_COLD);
+    }
+    /*
+     * if obj is leaving a bus under reset, we need to ensure
+     * hold phase is not pending.
+     */
+    if (oldp_count && s->hold_phase_pending) {
+        resettable_phase_hold(obj, NULL, RESET_TYPE_COLD);
+    }
+    /* if oldp is more reset than newp */
+    for (uint32_t i = newp_count; i < oldp_count; i++) {
+        resettable_release_reset(obj, RESET_TYPE_COLD);
+    }
+}
+
 void resettable_class_set_parent_phases(ResettableClass *rc,
                                         ResettableEnterPhase enter,
                                         ResettableHoldPhase hold,
diff --git a/hw/core/trace-events b/hw/core/trace-events
index a2e43f1120..80e6325ab0 100644
--- a/hw/core/trace-events
+++ b/hw/core/trace-events
@@ -16,6 +16,7 @@ resettable_reset_assert_begin(void *obj, int cold) "obj=%p cold=%d"
 resettable_reset_assert_end(void *obj) "obj=%p"
 resettable_reset_release_begin(void *obj, int cold) "obj=%p cold=%d"
 resettable_reset_release_end(void *obj) "obj=%p"
+resettable_change_parent(void *obj, void *o, uint32_t oc, void *n, uint32_t nc) "obj=%p from=%p(%" PRIu32 ") to=%p(%" PRIu32 ")"
 resettable_phase_enter_begin(void *obj, const char *objtype, uint32_t count, int type) "obj=%p(%s) count=%" PRIu32 " type=%d"
 resettable_phase_enter_exec(void *obj, const char *objtype, int type, int has_method) "obj=%p(%s) type=%d method=%d"
 resettable_phase_enter_end(void *obj, const char *objtype, uint32_t count) "obj=%p(%s) count=%" PRIu32
-- 
2.24.1

[PATCH v7 06/11] hw/core/qdev: handle parent bus change regarding resettable

[Damien Hedde]

In qdev_set_parent_bus(), when changing the parent bus of a
realized device, if the source and destination buses are not in the
same reset state, some adaptations are required. This patch adds
needed call to resettable_change_parent() to make sure a device reset
state stays coherent with its parent bus.

The addition is a no-op if:
1. the device being parented is not realized.
2. the device is realized, but both buses are not under reset.

Case 2 means that as long as qdev_set_parent_bus() is called
during the machine realization procedure (which is before the
machine reset so nothing is in reset), it is a no op.

There are 52 call sites of qdev_set_parent_bus(). All but one fall
into the no-op case:
+ 29 trivial calls related to virtio (in hw/{s390x,display,virtio}/
  {vhost,virtio}-xxx.c) to set a vdev(or vgpu) composing device
  parent bus just before realizing the same vdev(vgpu).
+ hw/core/qdev.c: when creating a device in qdev_try_create()
+ hw/core/sysbus.c: when initializing a device in the sysbus
+ hw/i386/amd_iommu.c: before realizing AMDVIState/pci
+ hw/isa/piix4.c: before realizing PIIX4State/rtc
+ hw/misc/auxbus.c: when creating an AUXBus
+ hw/misc/auxbus.c: when creating an AUXBus child
+ hw/misc/macio/macio.c: when initializing a MACIOState child
+ hw/misc/macio/macio.c: before realizing NewWorldMacIOState/pmu
+ hw/misc/macio/macio.c: before realizing NewWorldMacIOState/cuda
+ hw/net/virtio-net.c: Used for migration when using the failover
                       mechanism to migration a vfio-pci/net. It is
                       a no-op because at this point the device is
                       already on the bus.
+ hw/pci-host/designware.c: before realizing DesignwarePCIEHost/root
+ hw/pci-host/gpex.c: before realizing GPEXHost/root
+ hw/pci-host/prep.c: when initializaing PREPPCIState/pci_dev
+ hw/pci-host/q35.c: before realizing Q35PCIHost/mch
+ hw/pci-host/versatile.c: when initializing PCIVPBState/pci_dev
+ hw/pci-host/xilinx-pcie.c: before realizing XilinxPCIEHost/root
+ hw/s390x/event-facility.c: when creating SCLPEventFacility/
                             TYPE_SCLP_QUIESCE
+ hw/s390x/event-facility.c: ditto with SCLPEventFacility/
                             TYPE_SCLP_CPU_HOTPLUG
+ hw/s390x/sclp.c: Not trivial because it is called on a SLCPDevice
  just after realizing it. Ok because at this point the destination
  bus (sysbus) is not in reset; the realize step is before the
  machine reset.
+ hw/sd/core.c: Not OK. Used in sdbus_reparent_card(). See below.
+ hw/ssi/ssi.c: Used to put spi slave on spi bus and connect the cs
  line in ssi_auto_connect_slave(). Ok because this function is only
  used in realize step in hw/ssi/aspeed_smc.ci, hw/ssi/imx_spi.c,
  hw/ssi/mss-spi.c, hw/ssi/xilinx_spi.c and hw/ssi/xilinx_spips.c.
+ hw/xen/xen-legacy-backend.c: when creating a XenLegacyDevice device
+ qdev-monitor.c: in device hotplug creation procedure before realize

Note that this commit alone will have no effect, right now there is no
use of resettable API to reset anything. So a bus will never be tagged
as in-reset by this same API.

The one place where side-effect will occurs is in hw/sd/core.c in
sdbus_reparent_card(). This function is only used in the raspi machines,
including during the sysbus reset procedure. This case will be
carrefully handled when doing the multiple phase reset transition.

Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
---

v6 update: there are now 3 more call sites (52 instead of 49).
+ hw/isa/piix4.c
+ hw/net/virtio-net.c
+ hw/virtio/vhost-user-fs-pci.c (in list below)

Exhaustive list of the 29 "virtio" caller to qdev_set_parent_bus():
+ hw/display/virtio-gpu-pci.c:     VirtIOGPUPCIBase/vgpu realize
+ hw/display/virtio-vga.c:         VirtIOVGABase/vgpu realize
+ hw/s390x/vhost-vsock-ccw.c:      VHostVSockCCWState/vdev realize
+ hw/s390x/virtio-ccw-9p.c:        V9fsCCWState/vdev realize
+ hw/s390x/virtio-ccw-balloon.c:   VirtIOBalloonCcw/vdev realize
+ hw/s390x/virtio-ccw-blk.c:       VirtIOBlkCcw/vdev realize
+ hw/s390x/virtio-ccw-crypto.c:    VirtIOCryptoCcw/vdev realize
+ hw/s390x/virtio-ccw-gpu.c:       VirtIOGPUCcw/vdev realize
+ hw/s390x/virtio-ccw-input.c:     VirtIOInputCcw/vdev realize
+ hw/s390x/virtio-ccw-net.c:       VirtIONetCcw/vdev realize
+ hw/s390x/virtio-ccw-rng.c:       VirtIORNGCcw/vdev realize
+ hw/s390x/virtio-ccw-scsi.c:      VirtIOSCSICcw/vdev realize
+ hw/s390x/virtio-ccw-scsi.c:      VHostSCSICcw/vdev realize
+ hw/s390x/virtio-ccw-serial.c:    VirtioSerialCcw/vdev realize
+ hw/virtio/vhost-scsi-pci.c:      VHostSCSIPCI/vdev realize
+ hw/virtio/vhost-user-blk-pci.c:  VHostUserBlkPCI/vdev realize
+ hw/virtio/vhost-user-fs-pci.c:   VHostUserFSPCI/vdev realize
+ hw/virtio/vhost-user-scsi-pci.c: VHostUserSCSIPCI/vdev realize
+ hw/virtio/vhost-vsock-pci.c:     VHostVSockPCI/vdev realize
+ hw/virtio/virtio-9p-pci.c:       V9fsPCIState/vdev realize
+ hw/virtio/virtio-balloon-pci.c:  VirtIOBalloonPCI/vdev realize
+ hw/virtio/virtio-blk-pci.c:      VirtIOBlkPCI/vdev realize
+ hw/virtio/virtio-crypto-pci.c:   VirtIOCryptoPCI/vdev realize
+ hw/virtio/virtio-input-pci.c:    VirtIOInputPCI/vdev realize
+ hw/virtio/virtio-net-pci.c:      VirtIONetPCI/vdev realize
+ hw/virtio/virtio-pmem-pci.c:     VirtIOPMEMPCI/vdev realize
+ hw/virtio/virtio-rng-pci.c:      VirtIORngPCI/vdev realize
+ hw/virtio/virtio-scsi-pci.c:     VirtIOSCSIPCI/vdev realize
+ hw/virtio/virtio-serial-pci.c:   VirtIOSerialPCI/vdev realize
---
 hw/core/qdev.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index d431a020fc..310b87e25a 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -96,25 +96,31 @@ static void bus_add_child(BusState *bus, DeviceState *child)
 
 void qdev_set_parent_bus(DeviceState *dev, BusState *bus)
 {
-    bool replugging = dev->parent_bus != NULL;
+    BusState *old_parent_bus = dev->parent_bus;
 
-    if (replugging) {
+    if (old_parent_bus) {
         trace_qdev_update_parent_bus(dev, object_get_typename(OBJECT(dev)),
-            dev->parent_bus, object_get_typename(OBJECT(dev->parent_bus)),
+            old_parent_bus, object_get_typename(OBJECT(old_parent_bus)),
             OBJECT(bus), object_get_typename(OBJECT(bus)));
         /*
          * Keep a reference to the device while it's not plugged into
          * any bus, to avoid it potentially evaporating when it is
          * dereffed in bus_remove_child().
+         * Also keep the ref of the parent bus until the end, so that
+         * we can safely call resettable_change_parent() below.
          */
         object_ref(OBJECT(dev));
         bus_remove_child(dev->parent_bus, dev);
-        object_unref(OBJECT(dev->parent_bus));
     }
     dev->parent_bus = bus;
     object_ref(OBJECT(bus));
     bus_add_child(bus, dev);
-    if (replugging) {
+    if (dev->realized) {
+        resettable_change_parent(OBJECT(dev), OBJECT(bus),
+                                 OBJECT(old_parent_bus));
+    }
+    if (old_parent_bus) {
+        object_unref(OBJECT(old_parent_bus));
         object_unref(OBJECT(dev));
     }
 }
-- 
2.24.1

[PATCH v7 07/11] hw/core/qdev: update hotplug reset regarding resettable

[Damien Hedde]

This commit make use of the resettable API to reset the device being
hotplugged when it is realized. Also it ensures it is put in a reset
state coherent with the parent it is plugged into.

Note that there is a difference in the reset. Instead of resetting
only the hotplugged device, we reset also its subtree (switch to
resettable API). This is not expected to be a problem because
sub-buses are just realized too. If a hotplugged device has any
sub-buses it is logical to reset them too at this point.

The recently added should_be_hidden and PCI's partially_hotplugged
mechanisms do not interfere with realize operation:
+ In the should_be_hidden use case, device creation is
delayed.
+ The partially_hotplugged mechanism prevents a device to be
unplugged and unrealized from qdev POV and unrealized.

Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
---

v7 update: inline resettable_state_clear()

v6 update: clear the reset state before doing any reset. Although it
is apparently highly improbable that a device be realized again after
being unrealized. See here for a discussion about this point and the
partially_hotplugged/shoud_be_hidden cases.
https://lists.nongnu.org/archive/html/qemu-devel/2019-11/msg04897.html
---
 include/hw/resettable.h | 11 +++++++++++
 hw/core/qdev.c          | 15 ++++++++++++++-
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/include/hw/resettable.h b/include/hw/resettable.h
index 3c87ab86c7..3f90da5b5b 100644
--- a/include/hw/resettable.h
+++ b/include/hw/resettable.h
@@ -153,6 +153,17 @@ struct ResettableState {
     bool exit_phase_in_progress;
 };
 
+/**
+ * resettable_state_clear:
+ * Clear the state. It puts the state to the initial (zeroed) state required
+ * to reuse an object. Typically used in realize step of base classes
+ * implementing the interface.
+ */
+static inline void resettable_state_clear(ResettableState *state)
+{
+    memset(state, 0, sizeof(ResettableState));
+}
+
 /**
  * resettable_reset:
  * Trigger a reset on an object @obj of type @type. @obj must implement
diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index 310b87e25a..5fac4cd8fc 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -937,6 +937,12 @@ static void device_set_realized(Object *obj, bool value, Error **errp)
             }
         }
 
+        /*
+         * Clear the reset state, in case the object was previously unrealized
+         * with a dirty state.
+         */
+        resettable_state_clear(&dev->reset);
+
         QLIST_FOREACH(bus, &dev->child_bus, sibling) {
             object_property_set_bool(OBJECT(bus), true, "realized",
                                          &local_err);
@@ -945,7 +951,14 @@ static void device_set_realized(Object *obj, bool value, Error **errp)
             }
         }
         if (dev->hotplugged) {
-            device_legacy_reset(dev);
+            /*
+             * Reset the device, as well as its subtree which, at this point,
+             * should be realized too.
+             */
+            resettable_assert_reset(OBJECT(dev), RESET_TYPE_COLD);
+            resettable_change_parent(OBJECT(dev), OBJECT(dev->parent_bus),
+                                     NULL);
+            resettable_release_reset(OBJECT(dev), RESET_TYPE_COLD);
         }
         dev->pending_deleted_event = false;
 
-- 
2.24.1

[PATCH v7 08/11] hw/core: deprecate old reset functions and introduce new ones

[Damien Hedde]

Deprecate device_legacy_reset(), qdev_reset_all() and
qbus_reset_all() to be replaced by new functions
device_cold_reset() and bus_cold_reset() which uses resettable API.

Also introduce resettable_cold_reset_fn() which may be used as a
replacement for qdev_reset_all_fn and qbus_reset_all_fn().

Following patches will be needed to look at legacy reset call sites
and switch to resettable api. The legacy functions will be removed
when unused.

Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
---
 include/hw/qdev-core.h  | 27 +++++++++++++++++++++++++++
 include/hw/resettable.h |  9 +++++++++
 hw/core/bus.c           |  5 +++++
 hw/core/qdev.c          |  5 +++++
 hw/core/resettable.c    |  5 +++++
 5 files changed, 51 insertions(+)

diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
index 1b4b420617..b84fcc32bf 100644
--- a/include/hw/qdev-core.h
+++ b/include/hw/qdev-core.h
@@ -406,6 +406,13 @@ int qdev_walk_children(DeviceState *dev,
                        qdev_walkerfn *post_devfn, qbus_walkerfn *post_busfn,
                        void *opaque);
 
+/**
+ * @qdev_reset_all:
+ * Reset @dev. See @qbus_reset_all() for more details.
+ *
+ * Note: This function is deprecated and will be removed when it becomes unused.
+ * Please use device_cold_reset() now.
+ */
 void qdev_reset_all(DeviceState *dev);
 void qdev_reset_all_fn(void *opaque);
 
@@ -418,10 +425,28 @@ void qdev_reset_all_fn(void *opaque);
  * hard reset means that qbus_reset_all will reset all state of the device.
  * For PCI devices, for example, this will include the base address registers
  * or configuration space.
+ *
+ * Note: This function is deprecated and will be removed when it becomes unused.
+ * Please use bus_cold_reset() now.
  */
 void qbus_reset_all(BusState *bus);
 void qbus_reset_all_fn(void *opaque);
 
+/**
+ * device_cold_reset:
+ * Reset device @dev and perform a recursive processing using the resettable
+ * interface. It triggers a RESET_TYPE_COLD.
+ */
+void device_cold_reset(DeviceState *dev);
+
+/**
+ * bus_cold_reset:
+ *
+ * Reset bus @bus and perform a recursive processing using the resettable
+ * interface. It triggers a RESET_TYPE_COLD.
+ */
+void bus_cold_reset(BusState *bus);
+
 /**
  * device_is_in_reset:
  * Return true if the device @dev is currently being reset.
@@ -452,6 +477,8 @@ void qdev_machine_init(void);
  * device_legacy_reset:
  *
  * Reset a single device (by calling the reset method).
+ * Note: This function is deprecated and will be removed when it becomes unused.
+ * Please use device_cold_reset() now.
  */
 void device_legacy_reset(DeviceState *dev);
 
diff --git a/include/hw/resettable.h b/include/hw/resettable.h
index 3f90da5b5b..0c1adf49ee 100644
--- a/include/hw/resettable.h
+++ b/include/hw/resettable.h
@@ -221,6 +221,15 @@ bool resettable_is_in_reset(Object *obj);
  */
 void resettable_change_parent(Object *obj, Object *newp, Object *oldp);
 
+/**
+ * resettable_cold_reset_fn:
+ * Helper to call resettable_reset((Object *) opaque, RESET_TYPE_COLD).
+ *
+ * This function is typically useful to register a reset handler with
+ * qemu_register_reset.
+ */
+void resettable_cold_reset_fn(void *opaque);
+
 /**
  * resettable_class_set_parent_phases:
  *
diff --git a/hw/core/bus.c b/hw/core/bus.c
index 2698f715bd..3dc0a825f0 100644
--- a/hw/core/bus.c
+++ b/hw/core/bus.c
@@ -68,6 +68,11 @@ int qbus_walk_children(BusState *bus,
     return 0;
 }
 
+void bus_cold_reset(BusState *bus)
+{
+    resettable_reset(OBJECT(bus), RESET_TYPE_COLD);
+}
+
 bool bus_is_in_reset(BusState *bus)
 {
     return resettable_is_in_reset(OBJECT(bus));
diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index 5fac4cd8fc..a7a7abe569 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -361,6 +361,11 @@ void qbus_reset_all_fn(void *opaque)
     qbus_reset_all(bus);
 }
 
+void device_cold_reset(DeviceState *dev)
+{
+    resettable_reset(OBJECT(dev), RESET_TYPE_COLD);
+}
+
 bool device_is_in_reset(DeviceState *dev)
 {
     return resettable_is_in_reset(OBJECT(dev));
diff --git a/hw/core/resettable.c b/hw/core/resettable.c
index e99bb30058..7647ef6863 100644
--- a/hw/core/resettable.c
+++ b/hw/core/resettable.c
@@ -264,6 +264,11 @@ void resettable_change_parent(Object *obj, Object *newp, Object *oldp)
     }
 }
 
+void resettable_cold_reset_fn(void *opaque)
+{
+    resettable_reset((Object *) opaque, RESET_TYPE_COLD);
+}
+
 void resettable_class_set_parent_phases(ResettableClass *rc,
                                         ResettableEnterPhase enter,
                                         ResettableHoldPhase hold,
-- 
2.24.1

[PATCH v7 09/11] docs/devel/reset.rst: add doc about Resettable interface

[Damien Hedde]

Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
---
 docs/devel/index.rst |   1 +
 docs/devel/reset.rst | 289 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 290 insertions(+)
 create mode 100644 docs/devel/reset.rst

diff --git a/docs/devel/index.rst b/docs/devel/index.rst
index ac862152dc..4dc2ca8d71 100644
--- a/docs/devel/index.rst
+++ b/docs/devel/index.rst
@@ -24,3 +24,4 @@ Contents:
    tcg
    tcg-plugins
    bitops
+   reset
diff --git a/docs/devel/reset.rst b/docs/devel/reset.rst
new file mode 100644
index 0000000000..abea1102dc
--- /dev/null
+++ b/docs/devel/reset.rst
@@ -0,0 +1,289 @@
+
+=======================================
+Reset in QEMU: the Resettable interface
+=======================================
+
+The reset of qemu objects is handled using the resettable interface declared
+in ``include/hw/resettable.h``.
+
+This interface allows objects to be grouped (on a tree basis); so that the
+whole group can be reset consistently. Each individual member object does not
+have to care about others; in particular, problems of order (which object is
+reset first) are addressed.
+
+As of now DeviceClass and BusClass implement this interface.
+
+
+Triggering reset
+----------------
+
+This section documents the APIs which "users" of a resettable object should use
+to control it. All resettable control functions must be called while holding
+the iothread lock.
+
+You can apply a reset to an object using ``resettable_assert_reset()``. You need
+to call ``resettable_release_reset()`` to release the object from reset. To
+instantly reset an object, without keeping it in reset state, just call
+``resettable_reset()``. These functions take two parameters: a pointer to the
+object to reset and a reset type.
+
+Several types of reset will be supported. For now only cold reset is defined;
+others may be added later. The Resettable interface handles reset types with an
+enum:
+
+``RESET_TYPE_COLD``
+  Cold reset is supported by every resettable object. In QEMU, it means we reset
+  to the initial state corresponding to the start of QEMU; this might differ
+  from what is a real hardware cold reset. It differs from other resets (like
+  warm or bus resets) which may keep certain parts untouched.
+
+Calling ``resettable_reset()`` is equivalent to calling
+``resettable_assert_reset()`` then ``resettable_release_reset()``. It is
+possible to interleave multiple calls to these three functions. There may
+be several reset sources/controllers of a given object. The interface handles
+everything and the different reset controllers do not need to know anything
+about each others. The object will leave reset state only when each other
+controllers end their reset operation. This point is handled internally by
+maintaining a count of in-progress resets; it is crucial to call
+``resettable_release_reset()`` one time and only one time per
+``resettable_assert_reset()`` call.
+
+For now migration of a device or bus in reset is not supported. Care must be
+taken not to delay ``resettable_release_reset()`` after its
+``resettable_assert_reset()`` counterpart.
+
+Note that, since resettable is an interface, the API takes a simple Object as
+parameter. Still, it is a programming error to call a resettable function on a
+non-resettable object and it will trigger a run time assert error. Since most
+calls to resettable interface are done through base class functions, such an
+error is not likely to happen.
+
+For Devices and Buses, the following helper functions exist:
+
+- ``device_cold_reset()``
+- ``bus_cold_reset()``
+
+These are simple wrappers around resettable_reset() function; they only cast the
+Device or Bus into an Object and pass the cold reset type. When possible
+prefer to use these functions instead of ``resettable_reset()``.
+
+Device and bus functions co-exist because there can be semantic differences
+between resetting a bus and resetting the controller bridge which owns it.
+For example, consider a SCSI controller. Resetting the controller puts all
+its registers back to what reset state was as well as reset everything on the
+SCSI bus, whereas resetting just the SCSI bus only resets everything that's on
+it but not the controller.
+
+
+Multi-phase mechanism
+---------------------
+
+This section documents the internals of the resettable interface.
+
+The resettable interface uses a multi-phase system to relieve objects and
+machines from reset ordering problems. To address this, the reset operation
+of an object is split into three well defined phases.
+
+When resetting several objects (for example the whole machine at simulation
+startup), all first phases of all objects are executed, then all second phases
+and then all third phases.
+
+The three phases are:
+
+1. The **enter** phase is executed when the object enters reset. It resets only
+   local state of the object; it must not do anything that has a side-effect
+   on other objects, such as raising or lowering a qemu_irq line or reading or
+   writing guest memory.
+
+2. The **hold** phase is executed for entry into reset, once every object in the
+   group which is being reset has had its *enter* phase executed. At this point
+   devices can do actions that affect other objects.
+
+3. The **exit** phase is executed when the object leaves the reset state.
+   Actions affecting other objects are permitted.
+
+As said in previous section, the interface maintains a count of reset. This
+count is used to ensure phases are executed only when required. *enter* and
+*hold* phases are executed only when asserting reset for the first time
+(if an object is already in reset state when calling
+``resettable_assert_reset()`` or ``resettable_reset()``, they are not
+executed).
+The *exit* phase is executed only when the last reset operation ends. Therefore
+the object does not need to care how many of reset controllers it has and how
+many of them have started a reset.
+
+
+Handling reset in a resettable object
+-------------------------------------
+
+This section documents the APIs that an implementation of a resettable object
+must provide and what functions it has access to. It is intended for people
+who want to implement or convert a class which has the resettable interface;
+for example when specializing an existing device or bus.
+
+Methods to implement
+....................
+
+Three methods should be defined or left empty. Each method corresponds to a
+phase of the reset; they are name ``phases.enter()``, ``phases.hold()`` and
+``phases.exit()``. They all take the object as parameter. The *enter* method
+also take the reset type as second parameter.
+
+When extending an existing class, these methods may need to be extended too.
+The ``resettable_class_set_parent_phases()`` class function may be used to
+backup parent class methods.
+
+Here follows an example to implement reset for a Device which sets an IO while
+in reset.
+
+::
+
+    static void mydev_reset_enter(Object *obj, ResetType type)
+    {
+        MyDevClass *myclass = MYDEV_GET_CLASS(obj);
+        MyDevState *mydev = MYDEV(obj);
+        /* call parent class enter phase */
+        if (myclass->parent_phases.enter) {
+            myclass->parent_phases.enter(obj, type);
+        }
+        /* initialize local state only */
+        mydev->var = 0;
+    }
+
+    static void mydev_reset_hold(Object *obj)
+    {
+        MyDevClass *myclass = MYDEV_GET_CLASS(obj);
+        MyDevState *mydev = MYDEV(obj);
+        /* call parent class hold phase */
+        if (myclass->parent_phases.hold) {
+            myclass->parent_phases.hold(obj);
+        }
+        /* set an IO */
+        qemu_set_irq(mydev->irq, 1);
+    }
+
+    static void mydev_reset_exit(Object *obj)
+    {
+        MyDevClass *myclass = MYDEV_GET_CLASS(obj);
+        MyDevState *mydev = MYDEV(obj);
+        /* call parent class exit phase */
+        if (myclass->parent_phases.exit) {
+            myclass->parent_phases.exit(obj);
+        }
+        /* clear an IO */
+        qemu_set_irq(mydev->irq, 0);
+    }
+
+    typedef struct MyDevClass {
+        MyParentClass parent_class;
+        /* to store eventual parent reset methods */
+        ResettablePhases parent_phases;
+    } MyDevClass;
+
+    static void mydev_class_init(ObjectClass *class, void *data)
+    {
+        MyDevClass *myclass = MYDEV_CLASS(class);
+        ResettableClass *rc = RESETTABLE_CLASS(class);
+        resettable_class_set_parent_reset_phases(rc,
+                                                 mydev_reset_enter,
+                                                 mydev_reset_hold,
+                                                 mydev_reset_exit,
+                                                 &myclass->parent_phases);
+    }
+
+In the above example, we override all three phases. It is possible to override
+only some of them by passing NULL instead of a function pointer to
+``resettable_class_set_parent_reset_phases()``. For example, the following will
+only override the *enter* phase and leave *hold* and *exit* untouched::
+
+    resettable_class_set_parent_reset_phases(rc, mydev_reset_enter,
+                                             NULL, NULL,
+                                             &myclass->parent_phases);
+
+This is equivalent to providing a trivial implementation of the hold and exit
+phases which does nothing but call the parent class's implementation of the
+phase.
+
+Polling the reset state
+.......................
+
+Resettable interface provides the ``resettable_is_in_reset()`` function.
+This function returns true if the object parameter is currently under reset.
+
+An object is under reset from the beginning of the *init* phase to the end of
+the *exit* phase. During all three phases, the function will return that the
+object is in reset.
+
+This function may be used if the object behavior has to be adapted
+while in reset state. For example if a device has an irq input,
+it will probably need to ignore it while in reset; then it can for
+example check the reset state at the beginning of the irq callback.
+
+Note that until migration of the reset state is supported, an object
+should not be left in reset. So apart from being currently executing
+one of the reset phases, the only cases when this function will return
+true is if an external interaction (like changing an io) is made during
+*hold* or *exit* phase of another object in the same reset group.
+
+Helpers ``device_is_in_reset()`` and ``bus_is_in_reset()`` are also provided
+for devices and buses and should be preferred.
+
+
+Base class handling of reset
+----------------------------
+
+This section documents parts of the reset mechanism that you only need to know
+about if you are extending it to work with a new base class other than
+DeviceClass or BusClass, or maintaining the existing code in those classes. Most
+people can ignore it.
+
+Methods to implement
+....................
+
+There are two other methods that need to exist in a class implementing the
+interface: ``get_state()`` and ``child_foreach()``.
+
+``get_state()`` is simple. *resettable* is an interface and, as a consequence,
+does not have any class state structure. But in order to factorize the code, we
+need one. This method must return a pointer to ``ResettableState`` structure.
+The structure must be allocated by the base class; preferably it should be
+located inside the object instance structure.
+
+``child_foreach()`` is more complex. It should execute the given callback on
+every reset child of the given resettable object. All children must be
+resettable too. Additional parameters (a reset type and an opaque pointer) must
+be passed to the callback too.
+
+In ``DeviceClass`` and ``BusClass`` the ``ResettableState`` is located
+``DeviceState`` and ``BusState`` structure. ``child_foreach()`` is implemented
+to follow the bus hierarchy; for a bus, it calls the function on every child
+device; for a device, it calls the function on every bus child. When we reset
+the main system bus, we reset the whole machine bus tree.
+
+Changing a resettable parent
+............................
+
+One thing which should be taken care of by the base class is handling reset
+hierarchy changes.
+
+The reset hierarchy is supposed to be static and built during machine creation.
+But there are actually some exceptions. To cope with this, the resettable API
+provides ``resettable_change_parent()``. This function allows to set, update or
+remove the parent of a resettable object after machine creation is done. As
+parameters, it takes the object being moved, the old parent if any and the new
+parent if any.
+
+This function can be used at any time when not in a reset operation. During
+a reset operation it must be used only in *hold* phase. Using it in *enter* or
+*exit* phase is an error.
+Also it should not be used during machine creation, although it is harmless to
+do so: the function is a no-op as long as old and new parent are NULL or not
+in reset.
+
+There is currently 2 cases where this function is used:
+
+1. *device hotplug*; it means a new device is introduced on a live bus.
+
+2. *hot bus change*; it means an existing live device is added, moved or
+   removed in the bus hierarchy. At the moment, it occurs only in the raspi
+   machines for changing the sdbus used by sd card.
-- 
2.24.1

[PATCH v7 10/11] vl: replace deprecated qbus_reset_all registration

[Damien Hedde]

Replace deprecated qbus_reset_all by resettable_cold_reset_fn for
the sysbus reset registration.

Apart for the raspi machines, this does not impact the behavior
because:
+ at this point resettable just calls the old reset methods of devices
  and buses in the same order as qdev/qbus.
+ resettable handlers registered with qemu_register_reset are
  serialized; there is no interleaving.
+ eventual explicit calls to legacy reset API (device_reset or
  qdev/qbus_reset) inside this reset handler will not be masked out
  by resettable mechanism; they do not go through resettable api.

For the raspi machines, during the sysbus reset the sd-card is not
reset twice anymore but only once. This is a consequence of switching
both sysbus reset and changing parent to resettable; it detects the
second reset is not needed. This has no impact on the state after
reset; the sd-card reset method only reset local state and query
information from the block backend.

Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
---

The raspi reset change can be observed by using the following command
(reset will occurs, then do Ctrl-C to end qemu; no firmware is
given here).
qemu-system-aarch64 -M raspi3 \
    -trace resettable_phase_hold_exec \
    -trace qdev_update_parent_bus \
    -trace resettable_change_parent \
    -trace qdev_reset -trace qbus_reset

Before the patch, the qdev/qbus_reset traces show when reset method are
called. After the patch, the resettable_phase_hold_exec show when reset
method are called.

The traced reset order of the raspi3 is listed below. I've added empty
lines and the tree structure.

 +->bcm2835-peripherals reset
 |
 |       +->sd-card reset
 |   +->sd-bus reset
 +->bcm2835_gpio reset
 |      -> dev_update_parent_bus (move the sd-card on the sdhci-bus)
 |      -> resettable_change_parent
 |
 +->bcm2835-dma reset
 |
 |   +->bcm2835-sdhost-bus reset
 +->bcm2835-sdhost reset
 |
 |       +->sd-card (reset ONLY BEFORE BEFORE THE PATCH)
 |   +->sdhci-bus reset
 +->generic-sdhci reset
 |
 +->bcm2835-rng reset
 +->bcm2835-property reset
 +->bcm2835-fb reset
 +->bcm2835-mbox reset
 +->bcm2835-aux reset
 +->pl011 reset
 +->bcm2835-ic reset
 +->bcm2836-control reset
System reset

In both case, the sd-card is reset (being on bcm2835_gpio/sd-bus) then moved
to generic-sdhci/sdhci-bus by the bcm2835_gpio reset method.

Before the patch, it is then reset again being part of generic-sdhci/sdhci-bus.
After the patch, it considered again for reset but its reset method is not
called because it is already flagged as reset.
---
 vl.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/vl.c b/vl.c
index 751401214c..e5a537d4f9 100644
--- a/vl.c
+++ b/vl.c
@@ -4362,7 +4362,15 @@ int main(int argc, char **argv, char **envp)
 
     /* TODO: once all bus devices are qdevified, this should be done
      * when bus is created by qdev.c */
-    qemu_register_reset(qbus_reset_all_fn, sysbus_get_default());
+    /*
+     * TODO: If we had a main 'reset container' that the whole system
+     * lived in, we could reset that using the multi-phase reset
+     * APIs. For the moment, we just reset the sysbus, which will cause
+     * all devices hanging off it (and all their child buses, recursively)
+     * to be reset. Note that this will *not* reset any Device objects
+     * which are not attached to some part of the qbus tree!
+     */
+    qemu_register_reset(resettable_cold_reset_fn, sysbus_get_default());
     qemu_run_machine_init_done_notifiers();
 
     if (rom_check_and_register_reset() != 0) {
-- 
2.24.1

[PATCH v7 11/11] hw/s390x/ipl: replace deprecated qdev_reset_all registration

[Damien Hedde]

Replace deprecated qdev_reset_all by resettable_cold_reset_fn for
the ipl registration in the main reset handlers.

This does not impact the behavior for the following reasons:
+ at this point resettable just call the old reset methods of devices
  and buses in the same order than qdev/qbus.
+ resettable handlers registered with qemu_register_reset are
  serialized; there is no interleaving.
+ eventual explicit calls to legacy reset API (device_reset or
  qdev/qbus_reset) inside this reset handler will not be masked out
  by resettable mechanism; they do not go through resettable api.

Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
---
Cc: qemu-s390x@nongnu.org
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Thomas Huth <thuth@redhat.com>
---
 hw/s390x/ipl.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/hw/s390x/ipl.c b/hw/s390x/ipl.c
index ca544d64c5..2689f7a017 100644
--- a/hw/s390x/ipl.c
+++ b/hw/s390x/ipl.c
@@ -237,7 +237,15 @@ static void s390_ipl_realize(DeviceState *dev, Error **errp)
      */
     ipl->compat_start_addr = ipl->start_addr;
     ipl->compat_bios_start_addr = ipl->bios_start_addr;
-    qemu_register_reset(qdev_reset_all_fn, dev);
+    /*
+     * Because this Device is not on any bus in the qbus tree (it is
+     * not a sysbus device and it's not on some other bus like a PCI
+     * bus) it will not be automatically reset by the 'reset the
+     * sysbus' hook registered by vl.c like most devices. So we must
+     * manually register a reset hook for it.
+     * TODO: there should be a better way to do this.
+     */
+    qemu_register_reset(resettable_cold_reset_fn, dev);
 error:
     error_propagate(errp, err);
 }
-- 
2.24.1

Re: [PATCH v7 10/11] vl: replace deprecated qbus_reset_all registration

[Philippe Mathieu-Daudé]

On 1/15/20 1:36 PM, Damien Hedde wrote:
> Replace deprecated qbus_reset_all by resettable_cold_reset_fn for
> the sysbus reset registration.
> 
> Apart for the raspi machines, this does not impact the behavior
> because:
> + at this point resettable just calls the old reset methods of devices
>    and buses in the same order as qdev/qbus.
> + resettable handlers registered with qemu_register_reset are
>    serialized; there is no interleaving.
> + eventual explicit calls to legacy reset API (device_reset or
>    qdev/qbus_reset) inside this reset handler will not be masked out
>    by resettable mechanism; they do not go through resettable api.
> 
> For the raspi machines, during the sysbus reset the sd-card is not
> reset twice anymore but only once. This is a consequence of switching
> both sysbus reset and changing parent to resettable; it detects the
> second reset is not needed. This has no impact on the state after
> reset; the sd-card reset method only reset local state and query
> information from the block backend.
> 
> Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
> Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
> ---
> 
> The raspi reset change can be observed by using the following command
> (reset will occurs, then do Ctrl-C to end qemu; no firmware is
> given here).
> qemu-system-aarch64 -M raspi3 \
>      -trace resettable_phase_hold_exec \
>      -trace qdev_update_parent_bus \
>      -trace resettable_change_parent \
>      -trace qdev_reset -trace qbus_reset
> 
> Before the patch, the qdev/qbus_reset traces show when reset method are
> called. After the patch, the resettable_phase_hold_exec show when reset
> method are called.
> 
> The traced reset order of the raspi3 is listed below. I've added empty
> lines and the tree structure.
> 
>   +->bcm2835-peripherals reset
>   |
>   |       +->sd-card reset
>   |   +->sd-bus reset
>   +->bcm2835_gpio reset
>   |      -> dev_update_parent_bus (move the sd-card on the sdhci-bus)
>   |      -> resettable_change_parent
>   |
>   +->bcm2835-dma reset
>   |
>   |   +->bcm2835-sdhost-bus reset
>   +->bcm2835-sdhost reset
>   |
>   |       +->sd-card (reset ONLY BEFORE BEFORE THE PATCH)
>   |   +->sdhci-bus reset
>   +->generic-sdhci reset
>   |
>   +->bcm2835-rng reset
>   +->bcm2835-property reset
>   +->bcm2835-fb reset
>   +->bcm2835-mbox reset
>   +->bcm2835-aux reset
>   +->pl011 reset
>   +->bcm2835-ic reset
>   +->bcm2836-control reset
> System reset
> 
> In both case, the sd-card is reset (being on bcm2835_gpio/sd-bus) then moved
> to generic-sdhci/sdhci-bus by the bcm2835_gpio reset method.
> 
> Before the patch, it is then reset again being part of generic-sdhci/sdhci-bus.
> After the patch, it considered again for reset but its reset method is not
> called because it is already flagged as reset.

I find this information helpful, have you considered including it in the 
description?

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>

> ---
>   vl.c | 10 +++++++++-
>   1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/vl.c b/vl.c
> index 751401214c..e5a537d4f9 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -4362,7 +4362,15 @@ int main(int argc, char **argv, char **envp)
>   
>       /* TODO: once all bus devices are qdevified, this should be done
>        * when bus is created by qdev.c */
> -    qemu_register_reset(qbus_reset_all_fn, sysbus_get_default());
> +    /*
> +     * TODO: If we had a main 'reset container' that the whole system
> +     * lived in, we could reset that using the multi-phase reset
> +     * APIs. For the moment, we just reset the sysbus, which will cause
> +     * all devices hanging off it (and all their child buses, recursively)
> +     * to be reset. Note that this will *not* reset any Device objects
> +     * which are not attached to some part of the qbus tree!
> +     */
> +    qemu_register_reset(resettable_cold_reset_fn, sysbus_get_default());
>       qemu_run_machine_init_done_notifiers();
>   
>       if (rom_check_and_register_reset() != 0) {
> 

Re: [PATCH v7 03/11] hw/core: create Resettable QOM interface

[Philippe Mathieu-Daudé]

On 1/15/20 1:36 PM, Damien Hedde wrote:
> This commit defines an interface allowing multi-phase reset. This aims
> to solve a problem of the actual single-phase reset (built in
> DeviceClass and BusClass): reset behavior is dependent on the order
> in which reset handlers are called. In particular doing external
> side-effect (like setting an qemu_irq) is problematic because receiving
> object may not be reset yet.
> 
> The Resettable interface divides the reset in 3 well defined phases.
> To reset an object tree, all 1st phases are executed then all 2nd then
> all 3rd. See the comments in include/hw/resettable.h for a more complete
> description. The interface defines 3 phases to let the future
> possibility of holding an object into reset for some time.
> 
> The qdev/qbus reset in DeviceClass and BusClass will be modified in
> following commits to use this interface. A mechanism is provided
> to allow executing a transitional reset handler in place of the 2nd
> phase which is executed in children-then-parent order inside a tree.
> This will allow to transition devices and buses smoothly while
> keeping the exact current qdev/qbus reset behavior for now.
> 
> Documentation will be added in a following commit.
> 
> Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
> ---
> 
> v7 update: un-nest struct ResettablePhases
> ---
>   Makefile.objs           |   1 +
>   include/hw/resettable.h | 211 +++++++++++++++++++++++++++++++++++
>   hw/core/resettable.c    | 238 ++++++++++++++++++++++++++++++++++++++++
>   hw/core/Makefile.objs   |   1 +
>   hw/core/trace-events    |  17 +++
>   5 files changed, 468 insertions(+)
>   create mode 100644 include/hw/resettable.h
>   create mode 100644 hw/core/resettable.c
> 
> diff --git a/Makefile.objs b/Makefile.objs
> index 7c1e50f9d6..9752d549b4 100644
> --- a/Makefile.objs
> +++ b/Makefile.objs
> @@ -191,6 +191,7 @@ trace-events-subdirs += migration
>   trace-events-subdirs += net
>   trace-events-subdirs += ui
>   endif
> +trace-events-subdirs += hw/core

TL;DR Duplicating this line breaks using the LTTng Userspace Tracer 
library (UST backend).

Probably because you started this series before commit 26b8e6dc42b got 
merged, Jun 13 2019!

Indeed Oct 02 2018...
https://www.mail-archive.com/qemu-devel@nongnu.org/msg564153.html

The problem is you (correctly) sorted alphabetically while Alexey 
appended at the end.

>   trace-events-subdirs += hw/display
>   trace-events-subdirs += qapi
>   trace-events-subdirs += qom
> diff --git a/include/hw/resettable.h b/include/hw/resettable.h
> new file mode 100644
> index 0000000000..58b3df4c22
> --- /dev/null
> +++ b/include/hw/resettable.h
> @@ -0,0 +1,211 @@
> +/*
> + * Resettable interface header.
> + *
> + * Copyright (c) 2019 GreenSocs SAS
> + *
> + * Authors:
> + *   Damien Hedde
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#ifndef HW_RESETTABLE_H
> +#define HW_RESETTABLE_H
> +
> +#include "qom/object.h"
> +
> +#define TYPE_RESETTABLE_INTERFACE "resettable"
> +
> +#define RESETTABLE_CLASS(class) \
> +    OBJECT_CLASS_CHECK(ResettableClass, (class), TYPE_RESETTABLE_INTERFACE)
> +
> +#define RESETTABLE_GET_CLASS(obj) \
> +    OBJECT_GET_CLASS(ResettableClass, (obj), TYPE_RESETTABLE_INTERFACE)
> +
> +typedef struct ResettableState ResettableState;
> +
> +/**
> + * ResetType:
> + * Types of reset.
> + *
> + * + Cold: reset resulting from a power cycle of the object.
> + *
> + * TODO: Support has to be added to handle more types. In particular,
> + * ResettableState structure needs to be expanded.
> + */
> +typedef enum ResetType {
> +    RESET_TYPE_COLD,
> +} ResetType;
> +
> +/*
> + * ResettableClass:
> + * Interface for resettable objects.
> + *
> + * See docs/devel/reset.rst for more detailed information about how QEMU models
> + * reset. This whole API must only be used when holding the iothread mutex.
> + *
> + * All objects which can be reset must implement this interface;
> + * it is usually provided by a base class such as DeviceClass or BusClass.
> + * Every Resettable object must maintain some state tracking the
> + * progress of a reset operation by providing a ResettableState structure.
> + * The functions defined in this module take care of updating the
> + * state of the reset.
> + * The base class implementation of the interface provides this
> + * state and implements the associated method: get_state.
> + *
> + * Concrete object implementations (typically specific devices
> + * such as a UART model) should provide the functions
> + * for the phases.enter, phases.hold and phases.exit methods, which
> + * they can set in their class init function, either directly or
> + * by calling resettable_class_set_parent_phases().
> + * The phase methods are guaranteed to only only ever be called once
> + * for any reset event, in the order 'enter', 'hold', 'exit'.
> + * An object will always move quickly from 'enter' to 'hold'
> + * but might remain in 'hold' for an arbitrary period of time
> + * before eventually reset is deasserted and the 'exit' phase is called.
> + * Object implementations should be prepared for functions handling
> + * inbound connections from other devices (such as qemu_irq handler
> + * functions) to be called at any point during reset after their
> + * 'enter' method has been called.
> + *
> + * Users of a resettable object should not call these methods
> + * directly, but instead use the function resettable_reset().
> + *
> + * @phases.enter: This phase is called when the object enters reset. It
> + * should reset local state of the object, but it must not do anything that
> + * has a side-effect on other objects, such as raising or lowering a qemu_irq
> + * line or reading or writing guest memory. It takes the reset's type as
> + * argument.
> + *
> + * @phases.hold: This phase is called for entry into reset, once every object
> + * in the system which is being reset has had its @phases.enter method called.
> + * At this point devices can do actions that affect other objects.
> + *
> + * @phases.exit: This phase is called when the object leaves the reset state.
> + * Actions affecting other objects are permitted.
> + *
> + * @get_state: Mandatory method which must return a pointer to a
> + * ResettableState.
> + *
> + * @get_transitional_function: transitional method to handle Resettable objects
> + * not yet fully moved to this interface. It will be removed as soon as it is
> + * not needed anymore. This method is optional and may return a pointer to a
> + * function to be used instead of the phases. If the method exists and returns
> + * a non-NULL function pointer then that function is executed as a replacement
> + * of the 'hold' phase method taking the object as argument. The two other phase
> + * methods are not executed.
> + *
> + * @child_foreach: Executes a given callback on every Resettable child. Child
> + * in this context means a child in the qbus tree, so the children of a qbus
> + * are the devices on it, and the children of a device are all the buses it
> + * owns. This is not the same as the QOM object hierarchy. The function takes
> + * additional opaque and ResetType arguments which must be passed unmodified to
> + * the callback.
> + */
> +typedef void (*ResettableEnterPhase)(Object *obj, ResetType type);
> +typedef void (*ResettableHoldPhase)(Object *obj);
> +typedef void (*ResettableExitPhase)(Object *obj);
> +typedef ResettableState * (*ResettableGetState)(Object *obj);
> +typedef void (*ResettableTrFunction)(Object *obj);
> +typedef ResettableTrFunction (*ResettableGetTrFunction)(Object *obj);
> +typedef void (*ResettableChildCallback)(Object *, void *opaque,
> +                                        ResetType type);
> +typedef void (*ResettableChildForeach)(Object *obj,
> +                                       ResettableChildCallback cb,
> +                                       void *opaque, ResetType type);
> +typedef struct ResettablePhases {
> +    ResettableEnterPhase enter;
> +    ResettableHoldPhase hold;
> +    ResettableExitPhase exit;
> +} ResettablePhases;
> +typedef struct ResettableClass {
> +    InterfaceClass parent_class;
> +
> +    /* Phase methods */
> +    ResettablePhases phases;
> +
> +    /* State access method */
> +    ResettableGetState get_state;
> +
> +    /* Transitional method for legacy reset compatibility */
> +    ResettableGetTrFunction get_transitional_function;
> +
> +    /* Hierarchy handling method */
> +    ResettableChildForeach child_foreach;
> +} ResettableClass;
> +
> +/**
> + * ResettableState:
> + * Structure holding reset related state. The fields should not be accessed
> + * directly; the definition is here to allow further inclusion into other
> + * objects.
> + *
> + * @count: Number of reset level the object is into. It is incremented when
> + * the reset operation starts and decremented when it finishes.
> + * @hold_phase_pending: flag which indicates that we need to invoke the 'hold'
> + * phase handler for this object.
> + * @exit_phase_in_progress: true if we are currently in the exit phase
> + */
> +struct ResettableState {
> +    uint32_t count;
> +    bool hold_phase_pending;
> +    bool exit_phase_in_progress;
> +};
> +
> +/**
> + * resettable_reset:
> + * Trigger a reset on an object @obj of type @type. @obj must implement
> + * Resettable interface.
> + *
> + * Calling this function is equivalent to calling @resettable_assert_reset()
> + * then @resettable_release_reset().
> + */
> +void resettable_reset(Object *obj, ResetType type);
> +
> +/**
> + * resettable_assert_reset:
> + * Put an object @obj into reset. @obj must implement Resettable interface.
> + *
> + * @resettable_release_reset() must eventually be called after this call.
> + * There must be one call to @resettable_release_reset() per call of
> + * @resettable_assert_reset(), with the same type argument.
> + *
> + * NOTE: Until support for migration is added, the @resettable_release_reset()
> + * must not be delayed. It must occur just after @resettable_assert_reset() so
> + * that migration cannot be triggered in between. Prefer using
> + * @resettable_reset() for now.
> + */
> +void resettable_assert_reset(Object *obj, ResetType type);
> +
> +/**
> + * resettable_release_reset:
> + * Release the object @obj from reset. @obj must implement Resettable interface.
> + *
> + * See @resettable_assert_reset() description for details.
> + */
> +void resettable_release_reset(Object *obj, ResetType type);
> +
> +/**
> + * resettable_is_in_reset:
> + * Return true if @obj is under reset.
> + *
> + * @obj must implement Resettable interface.
> + */
> +bool resettable_is_in_reset(Object *obj);
> +
> +/**
> + * resettable_class_set_parent_phases:
> + *
> + * Save @rc current reset phases into @parent_phases and override @rc phases
> + * by the given new methods (@enter, @hold and @exit).
> + * Each phase is overridden only if the new one is not NULL allowing to
> + * override a subset of phases.
> + */
> +void resettable_class_set_parent_phases(ResettableClass *rc,
> +                                        ResettableEnterPhase enter,
> +                                        ResettableHoldPhase hold,
> +                                        ResettableExitPhase exit,
> +                                        ResettablePhases *parent_phases);
> +
> +#endif
> diff --git a/hw/core/resettable.c b/hw/core/resettable.c
> new file mode 100644
> index 0000000000..9133208487
> --- /dev/null
> +++ b/hw/core/resettable.c
> @@ -0,0 +1,238 @@
> +/*
> + * Resettable interface.
> + *
> + * Copyright (c) 2019 GreenSocs SAS
> + *
> + * Authors:
> + *   Damien Hedde
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qemu/module.h"
> +#include "hw/resettable.h"
> +#include "trace.h"
> +
> +/**
> + * resettable_phase_enter/hold/exit:
> + * Function executing a phase recursively in a resettable object and its
> + * children.
> + */
> +static void resettable_phase_enter(Object *obj, void *opaque, ResetType type);
> +static void resettable_phase_hold(Object *obj, void *opaque, ResetType type);
> +static void resettable_phase_exit(Object *obj, void *opaque, ResetType type);
> +
> +/**
> + * enter_phase_in_progress:
> + * True if we are currently in reset enter phase.
> + *
> + * Note: This flag is only used to guarantee (using asserts) that the reset
> + * API is used correctly. We can use a global variable because we rely on the
> + * iothread mutex to ensure only one reset operation is in a progress at a
> + * given time.
> + */
> +static bool enter_phase_in_progress;
> +
> +void resettable_reset(Object *obj, ResetType type)
> +{
> +    trace_resettable_reset(obj, type);
> +    resettable_assert_reset(obj, type);
> +    resettable_release_reset(obj, type);
> +}
> +
> +void resettable_assert_reset(Object *obj, ResetType type)
> +{
> +    /* TODO: change this assert when adding support for other reset types */
> +    assert(type == RESET_TYPE_COLD);
> +    trace_resettable_reset_assert_begin(obj, type);
> +    assert(!enter_phase_in_progress);
> +
> +    enter_phase_in_progress = true;
> +    resettable_phase_enter(obj, NULL, type);
> +    enter_phase_in_progress = false;
> +
> +    resettable_phase_hold(obj, NULL, type);
> +
> +    trace_resettable_reset_assert_end(obj);
> +}
> +
> +void resettable_release_reset(Object *obj, ResetType type)
> +{
> +    /* TODO: change this assert when adding support for other reset types */
> +    assert(type == RESET_TYPE_COLD);
> +    trace_resettable_reset_release_begin(obj, type);
> +    assert(!enter_phase_in_progress);
> +
> +    resettable_phase_exit(obj, NULL, type);
> +
> +    trace_resettable_reset_release_end(obj);
> +}
> +
> +bool resettable_is_in_reset(Object *obj)
> +{
> +    ResettableClass *rc = RESETTABLE_GET_CLASS(obj);
> +    ResettableState *s = rc->get_state(obj);
> +
> +    return s->count > 0;
> +}
> +
> +/**
> + * resettable_child_foreach:
> + * helper to avoid checking the existence of the method.
> + */
> +static void resettable_child_foreach(ResettableClass *rc, Object *obj,
> +                                     ResettableChildCallback cb,
> +                                     void *opaque, ResetType type)
> +{
> +    if (rc->child_foreach) {
> +        rc->child_foreach(obj, cb, opaque, type);
> +    }
> +}
> +
> +/**
> + * resettable_get_tr_func:
> + * helper to fetch transitional reset callback if any.
> + */
> +static ResettableTrFunction resettable_get_tr_func(ResettableClass *rc,
> +                                                   Object *obj)
> +{
> +    ResettableTrFunction tr_func = NULL;
> +    if (rc->get_transitional_function) {
> +        tr_func = rc->get_transitional_function(obj);
> +    }
> +    return tr_func;
> +}
> +
> +static void resettable_phase_enter(Object *obj, void *opaque, ResetType type)
> +{
> +    ResettableClass *rc = RESETTABLE_GET_CLASS(obj);
> +    ResettableState *s = rc->get_state(obj);
> +    const char *obj_typename = object_get_typename(obj);
> +    bool action_needed = false;
> +
> +    /* exit phase has to finish properly before entering back in reset */
> +    assert(!s->exit_phase_in_progress);
> +
> +    trace_resettable_phase_enter_begin(obj, obj_typename, s->count, type);
> +
> +    /* Only take action if we really enter reset for the 1st time. */
> +    /*
> +     * TODO: if adding more ResetType support, some additional checks
> +     * are probably needed here.
> +     */
> +    if (s->count++ == 0) {
> +        action_needed = true;
> +    }
> +    /*
> +     * We limit the count to an arbitrary "big" value. The value is big
> +     * enough not to be triggered normally.
> +     * The assert will stop an infinite loop if there is a cycle in the
> +     * reset tree. The loop goes through resettable_foreach_child below
> +     * which at some point will call us again.
> +     */
> +    assert(s->count <= 50);
> +
> +    /*
> +     * handle the children even if action_needed is at false so that
> +     * child counts are incremented too
> +     */
> +    resettable_child_foreach(rc, obj, resettable_phase_enter, NULL, type);
> +
> +    /* execute enter phase for the object if needed */
> +    if (action_needed) {
> +        trace_resettable_phase_enter_exec(obj, obj_typename, type,
> +                                          !!rc->phases.enter);
> +        if (rc->phases.enter && !resettable_get_tr_func(rc, obj)) {
> +            rc->phases.enter(obj, type);
> +        }
> +        s->hold_phase_pending = true;
> +    }
> +    trace_resettable_phase_enter_end(obj, obj_typename, s->count);
> +}
> +
> +static void resettable_phase_hold(Object *obj, void *opaque, ResetType type)
> +{
> +    ResettableClass *rc = RESETTABLE_GET_CLASS(obj);
> +    ResettableState *s = rc->get_state(obj);
> +    const char *obj_typename = object_get_typename(obj);
> +
> +    /* exit phase has to finish properly before entering back in reset */
> +    assert(!s->exit_phase_in_progress);
> +
> +    trace_resettable_phase_hold_begin(obj, obj_typename, s->count, type);
> +
> +    /* handle children first */
> +    resettable_child_foreach(rc, obj, resettable_phase_hold, NULL, type);
> +
> +    /* exec hold phase */
> +    if (s->hold_phase_pending) {
> +        s->hold_phase_pending = false;
> +        ResettableTrFunction tr_func = resettable_get_tr_func(rc, obj);
> +        trace_resettable_phase_hold_exec(obj, obj_typename, !!rc->phases.hold);
> +        if (tr_func) {
> +            trace_resettable_transitional_function(obj, obj_typename);
> +            tr_func(obj);
> +        } else if (rc->phases.hold) {
> +            rc->phases.hold(obj);
> +        }
> +    }
> +    trace_resettable_phase_hold_end(obj, obj_typename, s->count);
> +}
> +
> +static void resettable_phase_exit(Object *obj, void *opaque, ResetType type)
> +{
> +    ResettableClass *rc = RESETTABLE_GET_CLASS(obj);
> +    ResettableState *s = rc->get_state(obj);
> +    const char *obj_typename = object_get_typename(obj);
> +
> +    assert(!s->exit_phase_in_progress);
> +    trace_resettable_phase_exit_begin(obj, obj_typename, s->count, type);
> +
> +    /* exit_phase_in_progress ensures this phase is 'atomic' */
> +    s->exit_phase_in_progress = true;
> +    resettable_child_foreach(rc, obj, resettable_phase_exit, NULL, type);
> +
> +    assert(s->count > 0);
> +    if (s->count == 1) {
> +        trace_resettable_phase_exit_exec(obj, obj_typename, !!rc->phases.exit);
> +        if (rc->phases.exit && !resettable_get_tr_func(rc, obj)) {
> +            rc->phases.exit(obj);
> +        }
> +        s->count = 0;
> +    }
> +    s->exit_phase_in_progress = false;
> +    trace_resettable_phase_exit_end(obj, obj_typename, s->count);
> +}
> +
> +void resettable_class_set_parent_phases(ResettableClass *rc,
> +                                        ResettableEnterPhase enter,
> +                                        ResettableHoldPhase hold,
> +                                        ResettableExitPhase exit,
> +                                        ResettablePhases *parent_phases)
> +{
> +    *parent_phases = rc->phases;
> +    if (enter) {
> +        rc->phases.enter = enter;
> +    }
> +    if (hold) {
> +        rc->phases.hold = hold;
> +    }
> +    if (exit) {
> +        rc->phases.exit = exit;
> +    }
> +}
> +
> +static const TypeInfo resettable_interface_info = {
> +    .name       = TYPE_RESETTABLE_INTERFACE,
> +    .parent     = TYPE_INTERFACE,
> +    .class_size = sizeof(ResettableClass),
> +};
> +
> +static void reset_register_types(void)
> +{
> +    type_register_static(&resettable_interface_info);
> +}
> +
> +type_init(reset_register_types)
> diff --git a/hw/core/Makefile.objs b/hw/core/Makefile.objs
> index 0edd9e635d..1709a122d4 100644
> --- a/hw/core/Makefile.objs
> +++ b/hw/core/Makefile.objs
> @@ -1,6 +1,7 @@
>   # core qdev-related obj files, also used by *-user:
>   common-obj-y += qdev.o qdev-properties.o
>   common-obj-y += bus.o reset.o
> +common-obj-y += resettable.o
>   common-obj-$(CONFIG_SOFTMMU) += qdev-fw.o
>   common-obj-$(CONFIG_SOFTMMU) += fw-path-provider.o
>   # irq.o needed for qdev GPIO handling:
> diff --git a/hw/core/trace-events b/hw/core/trace-events
> index a375aa88a4..a2e43f1120 100644
> --- a/hw/core/trace-events
> +++ b/hw/core/trace-events
> @@ -9,3 +9,20 @@ qbus_reset(void *obj, const char *objtype) "obj=%p(%s)"
>   qbus_reset_all(void *obj, const char *objtype) "obj=%p(%s)"
>   qbus_reset_tree(void *obj, const char *objtype) "obj=%p(%s)"
>   qdev_update_parent_bus(void *obj, const char *objtype, void *oldp, const char *oldptype, void *newp, const char *newptype) "obj=%p(%s) old_parent=%p(%s) new_parent=%p(%s)"
> +
> +# resettable.c
> +resettable_reset(void *obj, int cold) "obj=%p cold=%d"
> +resettable_reset_assert_begin(void *obj, int cold) "obj=%p cold=%d"
> +resettable_reset_assert_end(void *obj) "obj=%p"
> +resettable_reset_release_begin(void *obj, int cold) "obj=%p cold=%d"
> +resettable_reset_release_end(void *obj) "obj=%p"
> +resettable_phase_enter_begin(void *obj, const char *objtype, uint32_t count, int type) "obj=%p(%s) count=%" PRIu32 " type=%d"
> +resettable_phase_enter_exec(void *obj, const char *objtype, int type, int has_method) "obj=%p(%s) type=%d method=%d"
> +resettable_phase_enter_end(void *obj, const char *objtype, uint32_t count) "obj=%p(%s) count=%" PRIu32
> +resettable_phase_hold_begin(void *obj, const char *objtype, uint32_t count, int type) "obj=%p(%s) count=%" PRIu32 " type=%d"
> +resettable_phase_hold_exec(void *obj, const char *objtype, int has_method) "obj=%p(%s) method=%d"
> +resettable_phase_hold_end(void *obj, const char *objtype, uint32_t count) "obj=%p(%s) count=%" PRIu32
> +resettable_phase_exit_begin(void *obj, const char *objtype, uint32_t count, int type) "obj=%p(%s) count=%" PRIu32 " type=%d"
> +resettable_phase_exit_exec(void *obj, const char *objtype, int has_method) "obj=%p(%s) method=%d"
> +resettable_phase_exit_end(void *obj, const char *objtype, uint32_t count) "obj=%p(%s) count=%" PRIu32
> +resettable_transitional_function(void *obj, const char *objtype) "obj=%p(%s)"

Something here breaks ./configure --enable-trace-backends=ust:

   CC      trace-ust-all.o
In file included from trace-ust-all.h:13,
                  from trace-ust-all.c:13:
trace-ust-all.h:35151:1: error: redefinition of 
‘__tracepoint_cb_qemu___loader_write_rom’
35151 | TRACEPOINT_EVENT(
       | ^~~~~~~~~~~~~~~~
trace-ust-all.h:31791:1: note: previous definition of 
‘__tracepoint_cb_qemu___loader_write_rom’ was here
31791 | TRACEPOINT_EVENT(
       | ^~~~~~~~~~~~~~~~
...
./trace-ust-all.h:35388:1: error: redefinition of 
‘__tp_event_signature___qemu___resettable_transitional_function’
35388 | TRACEPOINT_EVENT(
       | ^~~~~~~~~~~~~~~~
./trace-ust-all.h:32028:1: note: previous definition of 
‘__tp_event_signature___qemu___resettable_transitional_function’ was here
32028 | TRACEPOINT_EVENT(
       | ^~~~~~~~~~~~~~~~
In file included from /usr/include/lttng/tracepoint-event.h:58,
                  from trace-ust-all.h:35401,
                  from trace-ust-all.c:13:

Indeed:

32028 TRACEPOINT_EVENT(
32029    qemu,
32030    resettable_transitional_function,
32031    TP_ARGS(void *, obj, const char *, objtype),
32032    TP_FIELDS(
32033        ctf_integer_hex(void *, obj, obj)
32034        ctf_string(objtype, objtype)
32035    )
32036 )
32037
...
35388 TRACEPOINT_EVENT(
35389    qemu,
35390    resettable_transitional_function,
35391    TP_ARGS(void *, obj, const char *, objtype),
35392    TP_FIELDS(
35393        ctf_integer_hex(void *, obj, obj)
35394        ctf_string(objtype, objtype)
35395    )
35396 )
35397
35398 #endif /* TRACE_ALL_GENERATED_UST_H */

Ah! I was going to say "no clue what could be wrong, so Cc'ing Stefan" 
but got it:

$ git grep hw/core Makefile.objs
Makefile.objs:194:trace-events-subdirs += hw/core
Makefile.objs:207:trace-events-subdirs += hw/core

We might already have a 'uniq' makefile function to do:

trace-events-subdirs = $(call uniq $(trace-events-subdirs))

or maybe was it with $filter? I can't find it/remember, too tired.

So the fix is:

-- >8 --
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -191,7 +191,6 @@ trace-events-subdirs += migration
  trace-events-subdirs += net
  trace-events-subdirs += ui
  endif
-trace-events-subdirs += hw/core
  trace-events-subdirs += hw/display
  trace-events-subdirs += qapi
  trace-events-subdirs += qom
---

Re: [PATCH v7 04/11] hw/core: add Resettable support to BusClass and DeviceClass

[Philippe Mathieu-Daudé]

On 1/15/20 1:36 PM, Damien Hedde wrote:
> This commit adds support of Resettable interface to buses and devices:
> + ResettableState structure is added in the Bus/Device state
> + Resettable methods are implemented.
> + device/bus_is_in_reset function defined
> 
> This commit allows to transition the objects to the new
> multi-phase interface without changing the reset behavior at all.
> Object single reset method can be split into the 3 different phases
> but the 3 phases are still executed in a row for a given object.
>  From the qdev/qbus reset api point of view, nothing is changed.
> qdev_reset_all() and qbus_reset_all() are not modified as well as
> device_legacy_reset().
> 
> Transition of an object must be done from parent class to child class.
> Care has been taken to allow the transition of a parent class
> without requiring the child classes to be transitioned at the same
> time. Note that SysBus and SysBusDevice class do not need any transition
> because they do not override the legacy reset method.
> 
> Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
> Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>

> ---
>   include/hw/qdev-core.h | 27 ++++++++++++
>   hw/core/bus.c          | 97 ++++++++++++++++++++++++++++++++++++++++++
>   hw/core/qdev.c         | 93 ++++++++++++++++++++++++++++++++++++++++
>   tests/Makefile.include |  1 +
>   4 files changed, 218 insertions(+)
> 
> diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
> index b8341b0fb0..1b4b420617 100644
> --- a/include/hw/qdev-core.h
> +++ b/include/hw/qdev-core.h
> @@ -5,6 +5,7 @@
>   #include "qemu/bitmap.h"
>   #include "qom/object.h"
>   #include "hw/hotplug.h"
> +#include "hw/resettable.h"
>   
>   enum {
>       DEV_NVECTORS_UNSPECIFIED = -1,
> @@ -117,6 +118,11 @@ typedef struct DeviceClass {
>       bool hotpluggable;
>   
>       /* callbacks */
> +    /*
> +     * Reset method here is deprecated and replaced by methods in the
> +     * resettable class interface to implement a multi-phase reset.
> +     * TODO: remove once every reset callback is unused
> +     */
>       DeviceReset reset;
>       DeviceRealize realize;
>       DeviceUnrealize unrealize;
> @@ -141,6 +147,7 @@ struct NamedGPIOList {
>   /**
>    * DeviceState:
>    * @realized: Indicates whether the device has been fully constructed.
> + * @reset: ResettableState for the device; handled by Resettable interface.
>    *
>    * This structure should not be accessed directly.  We declare it here
>    * so that it can be embedded in individual device state structures.
> @@ -163,6 +170,7 @@ struct DeviceState {
>       int num_child_bus;
>       int instance_id_alias;
>       int alias_required_for_version;
> +    ResettableState reset;
>   };
>   
>   struct DeviceListener {
> @@ -215,6 +223,7 @@ typedef struct BusChild {
>   /**
>    * BusState:
>    * @hotplug_handler: link to a hotplug handler associated with bus.
> + * @reset: ResettableState for the bus; handled by Resettable interface.
>    */
>   struct BusState {
>       Object obj;
> @@ -226,6 +235,7 @@ struct BusState {
>       int num_children;
>       QTAILQ_HEAD(, BusChild) children;
>       QLIST_ENTRY(BusState) sibling;
> +    ResettableState reset;
>   };
>   
>   /**
> @@ -412,6 +422,18 @@ void qdev_reset_all_fn(void *opaque);
>   void qbus_reset_all(BusState *bus);
>   void qbus_reset_all_fn(void *opaque);
>   
> +/**
> + * device_is_in_reset:
> + * Return true if the device @dev is currently being reset.
> + */
> +bool device_is_in_reset(DeviceState *dev);
> +
> +/**
> + * bus_is_in_reset:
> + * Return true if the bus @bus is currently being reset.
> + */
> +bool bus_is_in_reset(BusState *bus);
> +
>   /* This should go away once we get rid of the NULL bus hack */
>   BusState *sysbus_get_default(void);
>   
> @@ -433,6 +455,11 @@ void qdev_machine_init(void);
>    */
>   void device_legacy_reset(DeviceState *dev);
>   
> +/**
> + * device_class_set_parent_reset:
> + * TODO: remove the function when DeviceClass's reset method
> + * is not used anymore.
> + */
>   void device_class_set_parent_reset(DeviceClass *dc,
>                                      DeviceReset dev_reset,
>                                      DeviceReset *parent_reset);
> diff --git a/hw/core/bus.c b/hw/core/bus.c
> index 7f3d2a3dbd..2698f715bd 100644
> --- a/hw/core/bus.c
> +++ b/hw/core/bus.c
> @@ -68,6 +68,28 @@ int qbus_walk_children(BusState *bus,
>       return 0;
>   }
>   
> +bool bus_is_in_reset(BusState *bus)
> +{
> +    return resettable_is_in_reset(OBJECT(bus));
> +}
> +
> +static ResettableState *bus_get_reset_state(Object *obj)
> +{
> +    BusState *bus = BUS(obj);
> +    return &bus->reset;
> +}
> +
> +static void bus_reset_child_foreach(Object *obj, ResettableChildCallback cb,
> +                                    void *opaque, ResetType type)
> +{
> +    BusState *bus = BUS(obj);
> +    BusChild *kid;
> +
> +    QTAILQ_FOREACH(kid, &bus->children, sibling) {
> +        cb(OBJECT(kid->child), opaque, type);
> +    }
> +}
> +
>   static void qbus_realize(BusState *bus, DeviceState *parent, const char *name)
>   {
>       const char *typename = object_get_typename(OBJECT(bus));
> @@ -199,12 +221,83 @@ static char *default_bus_get_fw_dev_path(DeviceState *dev)
>       return g_strdup(object_get_typename(OBJECT(dev)));
>   }
>   
> +/**
> + * bus_phases_reset:
> + * Transition reset method for buses to allow moving
> + * smoothly from legacy reset method to multi-phases
> + */
> +static void bus_phases_reset(BusState *bus)
> +{
> +    ResettableClass *rc = RESETTABLE_GET_CLASS(bus);
> +
> +    if (rc->phases.enter) {
> +        rc->phases.enter(OBJECT(bus), RESET_TYPE_COLD);
> +    }
> +    if (rc->phases.hold) {
> +        rc->phases.hold(OBJECT(bus));
> +    }
> +    if (rc->phases.exit) {
> +        rc->phases.exit(OBJECT(bus));
> +    }
> +}
> +
> +static void bus_transitional_reset(Object *obj)
> +{
> +    BusClass *bc = BUS_GET_CLASS(obj);
> +
> +    /*
> +     * This will call either @bus_phases_reset (for multi-phases transitioned
> +     * buses) or a bus's specific method for not-yet transitioned buses.
> +     * In both case, it does not reset children.
> +     */
> +    if (bc->reset) {
> +        bc->reset(BUS(obj));
> +    }
> +}
> +
> +/**
> + * bus_get_transitional_reset:
> + * check if the bus's class is ready for multi-phase
> + */
> +static ResettableTrFunction bus_get_transitional_reset(Object *obj)
> +{
> +    BusClass *dc = BUS_GET_CLASS(obj);
> +    if (dc->reset != bus_phases_reset) {
> +        /*
> +         * dc->reset has been overridden by a subclass,
> +         * the bus is not ready for multi phase yet.
> +         */
> +        return bus_transitional_reset;
> +    }
> +    return NULL;
> +}
> +
>   static void bus_class_init(ObjectClass *class, void *data)
>   {
>       BusClass *bc = BUS_CLASS(class);
> +    ResettableClass *rc = RESETTABLE_CLASS(class);
>   
>       class->unparent = bus_unparent;
>       bc->get_fw_dev_path = default_bus_get_fw_dev_path;
> +
> +    rc->get_state = bus_get_reset_state;
> +    rc->child_foreach = bus_reset_child_foreach;
> +
> +    /*
> +     * @bus_phases_reset is put as the default reset method below, allowing
> +     * to do the multi-phase transition from base classes to leaf classes. It
> +     * allows a legacy-reset Bus class to extend a multi-phases-reset
> +     * Bus class for the following reason:
> +     * + If a base class B has been moved to multi-phase, then it does not
> +     *   override this default reset method and may have defined phase methods.
> +     * + A child class C (extending class B) which uses
> +     *   bus_class_set_parent_reset() (or similar means) to override the
> +     *   reset method will still work as expected. @bus_phases_reset function
> +     *   will be registered as the parent reset method and effectively call
> +     *   parent reset phases.
> +     */
> +    bc->reset = bus_phases_reset;
> +    rc->get_transitional_function = bus_get_transitional_reset;
>   }
>   
>   static void qbus_finalize(Object *obj)
> @@ -223,6 +316,10 @@ static const TypeInfo bus_info = {
>       .instance_init = qbus_initfn,
>       .instance_finalize = qbus_finalize,
>       .class_init = bus_class_init,
> +    .interfaces = (InterfaceInfo[]) {
> +        { TYPE_RESETTABLE_INTERFACE },
> +        { }
> +    },
>   };
>   
>   static void bus_register_types(void)
> diff --git a/hw/core/qdev.c b/hw/core/qdev.c
> index 5cb03136b5..d431a020fc 100644
> --- a/hw/core/qdev.c
> +++ b/hw/core/qdev.c
> @@ -355,6 +355,28 @@ void qbus_reset_all_fn(void *opaque)
>       qbus_reset_all(bus);
>   }
>   
> +bool device_is_in_reset(DeviceState *dev)
> +{
> +    return resettable_is_in_reset(OBJECT(dev));
> +}
> +
> +static ResettableState *device_get_reset_state(Object *obj)
> +{
> +    DeviceState *dev = DEVICE(obj);
> +    return &dev->reset;
> +}
> +
> +static void device_reset_child_foreach(Object *obj, ResettableChildCallback cb,
> +                                       void *opaque, ResetType type)
> +{
> +    DeviceState *dev = DEVICE(obj);
> +    BusState *bus;
> +
> +    QLIST_FOREACH(bus, &dev->child_bus, sibling) {
> +        cb(OBJECT(bus), opaque, type);
> +    }
> +}
> +
>   /* can be used as ->unplug() callback for the simple cases */
>   void qdev_simple_device_unplug_cb(HotplugHandler *hotplug_dev,
>                                     DeviceState *dev, Error **errp)
> @@ -1107,10 +1129,62 @@ device_vmstate_if_get_id(VMStateIf *obj)
>       return qdev_get_dev_path(dev);
>   }
>   
> +/**
> + * device_phases_reset:
> + * Transition reset method for devices to allow moving
> + * smoothly from legacy reset method to multi-phases
> + */
> +static void device_phases_reset(DeviceState *dev)
> +{
> +    ResettableClass *rc = RESETTABLE_GET_CLASS(dev);
> +
> +    if (rc->phases.enter) {
> +        rc->phases.enter(OBJECT(dev), RESET_TYPE_COLD);
> +    }
> +    if (rc->phases.hold) {
> +        rc->phases.hold(OBJECT(dev));
> +    }
> +    if (rc->phases.exit) {
> +        rc->phases.exit(OBJECT(dev));
> +    }
> +}
> +
> +static void device_transitional_reset(Object *obj)
> +{
> +    DeviceClass *dc = DEVICE_GET_CLASS(obj);
> +
> +    /*
> +     * This will call either @device_phases_reset (for multi-phases transitioned
> +     * devices) or a device's specific method for not-yet transitioned devices.
> +     * In both case, it does not reset children.
> +     */
> +    if (dc->reset) {
> +        dc->reset(DEVICE(obj));
> +    }
> +}
> +
> +/**
> + * device_get_transitional_reset:
> + * check if the device's class is ready for multi-phase
> + */
> +static ResettableTrFunction device_get_transitional_reset(Object *obj)
> +{
> +    DeviceClass *dc = DEVICE_GET_CLASS(obj);
> +    if (dc->reset != device_phases_reset) {
> +        /*
> +         * dc->reset has been overridden by a subclass,
> +         * the device is not ready for multi phase yet.
> +         */
> +        return device_transitional_reset;
> +    }
> +    return NULL;
> +}
> +
>   static void device_class_init(ObjectClass *class, void *data)
>   {
>       DeviceClass *dc = DEVICE_CLASS(class);
>       VMStateIfClass *vc = VMSTATE_IF_CLASS(class);
> +    ResettableClass *rc = RESETTABLE_CLASS(class);
>   
>       class->unparent = device_unparent;
>   
> @@ -1123,6 +1197,24 @@ static void device_class_init(ObjectClass *class, void *data)
>       dc->hotpluggable = true;
>       dc->user_creatable = true;
>       vc->get_id = device_vmstate_if_get_id;
> +    rc->get_state = device_get_reset_state;
> +    rc->child_foreach = device_reset_child_foreach;
> +
> +    /*
> +     * @device_phases_reset is put as the default reset method below, allowing
> +     * to do the multi-phase transition from base classes to leaf classes. It
> +     * allows a legacy-reset Device class to extend a multi-phases-reset
> +     * Device class for the following reason:
> +     * + If a base class B has been moved to multi-phase, then it does not
> +     *   override this default reset method and may have defined phase methods.
> +     * + A child class C (extending class B) which uses
> +     *   device_class_set_parent_reset() (or similar means) to override the
> +     *   reset method will still work as expected. @device_phases_reset function
> +     *   will be registered as the parent reset method and effectively call
> +     *   parent reset phases.
> +     */
> +    dc->reset = device_phases_reset;
> +    rc->get_transitional_function = device_get_transitional_reset;
>   }
>   
>   void device_class_set_parent_reset(DeviceClass *dc,
> @@ -1183,6 +1275,7 @@ static const TypeInfo device_type_info = {
>       .class_size = sizeof(DeviceClass),
>       .interfaces = (InterfaceInfo[]) {
>           { TYPE_VMSTATE_IF },
> +        { TYPE_RESETTABLE_INTERFACE },
>           { }
>       }
>   };
> diff --git a/tests/Makefile.include b/tests/Makefile.include
> index 1ae14a8b15..8ad07621b0 100644
> --- a/tests/Makefile.include
> +++ b/tests/Makefile.include
> @@ -427,6 +427,7 @@ tests/fp/%:
>   tests/test-qdev-global-props$(EXESUF): tests/test-qdev-global-props.o \
>   	hw/core/qdev.o hw/core/qdev-properties.o hw/core/hotplug.o\
>   	hw/core/bus.o \
> +	hw/core/resettable.o \
>   	hw/core/irq.o \
>   	hw/core/fw-path-provider.o \
>   	hw/core/reset.o \
> 

Re: [PATCH v7 02/11] hw/core/qdev: add trace events to help with resettable transition

[Philippe Mathieu-Daudé]

On 1/15/20 1:36 PM, Damien Hedde wrote:
> Adds trace events to reset procedure and when updating the parent
> bus of a device.
> 
> Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> Reviewed-by: Cornelia Huck <cohuck@redhat.com>

Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>

> ---
>   hw/core/qdev.c       | 29 ++++++++++++++++++++++++++---
>   hw/core/trace-events |  9 +++++++++
>   2 files changed, 35 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/core/qdev.c b/hw/core/qdev.c
> index 8c0c8284c8..5cb03136b5 100644
> --- a/hw/core/qdev.c
> +++ b/hw/core/qdev.c
> @@ -38,6 +38,7 @@
>   #include "hw/boards.h"
>   #include "hw/sysbus.h"
>   #include "migration/vmstate.h"
> +#include "trace.h"
>   
>   bool qdev_hotplug = false;
>   static bool qdev_hot_added = false;
> @@ -98,7 +99,11 @@ void qdev_set_parent_bus(DeviceState *dev, BusState *bus)
>       bool replugging = dev->parent_bus != NULL;
>   
>       if (replugging) {
> -        /* Keep a reference to the device while it's not plugged into
> +        trace_qdev_update_parent_bus(dev, object_get_typename(OBJECT(dev)),
> +            dev->parent_bus, object_get_typename(OBJECT(dev->parent_bus)),
> +            OBJECT(bus), object_get_typename(OBJECT(bus)));
> +        /*
> +         * Keep a reference to the device while it's not plugged into
>            * any bus, to avoid it potentially evaporating when it is
>            * dereffed in bus_remove_child().
>            */
> @@ -296,6 +301,18 @@ HotplugHandler *qdev_get_hotplug_handler(DeviceState *dev)
>       return hotplug_ctrl;
>   }
>   
> +static int qdev_prereset(DeviceState *dev, void *opaque)
> +{
> +    trace_qdev_reset_tree(dev, object_get_typename(OBJECT(dev)));
> +    return 0;
> +}
> +
> +static int qbus_prereset(BusState *bus, void *opaque)
> +{
> +    trace_qbus_reset_tree(bus, object_get_typename(OBJECT(bus)));
> +    return 0;
> +}
> +
>   static int qdev_reset_one(DeviceState *dev, void *opaque)
>   {
>       device_legacy_reset(dev);
> @@ -306,6 +323,7 @@ static int qdev_reset_one(DeviceState *dev, void *opaque)
>   static int qbus_reset_one(BusState *bus, void *opaque)
>   {
>       BusClass *bc = BUS_GET_CLASS(bus);
> +    trace_qbus_reset(bus, object_get_typename(OBJECT(bus)));
>       if (bc->reset) {
>           bc->reset(bus);
>       }
> @@ -314,7 +332,9 @@ static int qbus_reset_one(BusState *bus, void *opaque)
>   
>   void qdev_reset_all(DeviceState *dev)
>   {
> -    qdev_walk_children(dev, NULL, NULL, qdev_reset_one, qbus_reset_one, NULL);
> +    trace_qdev_reset_all(dev, object_get_typename(OBJECT(dev)));
> +    qdev_walk_children(dev, qdev_prereset, qbus_prereset,
> +                       qdev_reset_one, qbus_reset_one, NULL);
>   }
>   
>   void qdev_reset_all_fn(void *opaque)
> @@ -324,7 +344,9 @@ void qdev_reset_all_fn(void *opaque)
>   
>   void qbus_reset_all(BusState *bus)
>   {
> -    qbus_walk_children(bus, NULL, NULL, qdev_reset_one, qbus_reset_one, NULL);
> +    trace_qbus_reset_all(bus, object_get_typename(OBJECT(bus)));
> +    qbus_walk_children(bus, qdev_prereset, qbus_prereset,
> +                       qdev_reset_one, qbus_reset_one, NULL);
>   }
>   
>   void qbus_reset_all_fn(void *opaque)
> @@ -1131,6 +1153,7 @@ void device_legacy_reset(DeviceState *dev)
>   {
>       DeviceClass *klass = DEVICE_GET_CLASS(dev);
>   
> +    trace_qdev_reset(dev, object_get_typename(OBJECT(dev)));
>       if (klass->reset) {
>           klass->reset(dev);
>       }
> diff --git a/hw/core/trace-events b/hw/core/trace-events
> index fe47a9c8cb..a375aa88a4 100644
> --- a/hw/core/trace-events
> +++ b/hw/core/trace-events
> @@ -1,2 +1,11 @@
>   # loader.c
>   loader_write_rom(const char *name, uint64_t gpa, uint64_t size, bool isrom) "%s: @0x%"PRIx64" size=0x%"PRIx64" ROM=%d"
> +
> +# qdev.c
> +qdev_reset(void *obj, const char *objtype) "obj=%p(%s)"
> +qdev_reset_all(void *obj, const char *objtype) "obj=%p(%s)"
> +qdev_reset_tree(void *obj, const char *objtype) "obj=%p(%s)"
> +qbus_reset(void *obj, const char *objtype) "obj=%p(%s)"
> +qbus_reset_all(void *obj, const char *objtype) "obj=%p(%s)"
> +qbus_reset_tree(void *obj, const char *objtype) "obj=%p(%s)"
> +qdev_update_parent_bus(void *obj, const char *objtype, void *oldp, const char *oldptype, void *newp, const char *newptype) "obj=%p(%s) old_parent=%p(%s) new_parent=%p(%s)"
> 

Re: [PATCH v7 06/11] hw/core/qdev: handle parent bus change regarding resettable

[Philippe Mathieu-Daudé]

On 1/15/20 1:36 PM, Damien Hedde wrote:
> In qdev_set_parent_bus(), when changing the parent bus of a
> realized device, if the source and destination buses are not in the
> same reset state, some adaptations are required. This patch adds
> needed call to resettable_change_parent() to make sure a device reset
> state stays coherent with its parent bus.
> 
> The addition is a no-op if:
> 1. the device being parented is not realized.
> 2. the device is realized, but both buses are not under reset.
> 
> Case 2 means that as long as qdev_set_parent_bus() is called
> during the machine realization procedure (which is before the
> machine reset so nothing is in reset), it is a no op.
> 
> There are 52 call sites of qdev_set_parent_bus(). All but one fall
> into the no-op case:
> + 29 trivial calls related to virtio (in hw/{s390x,display,virtio}/
>    {vhost,virtio}-xxx.c) to set a vdev(or vgpu) composing device
>    parent bus just before realizing the same vdev(vgpu).
> + hw/core/qdev.c: when creating a device in qdev_try_create()
> + hw/core/sysbus.c: when initializing a device in the sysbus
> + hw/i386/amd_iommu.c: before realizing AMDVIState/pci
> + hw/isa/piix4.c: before realizing PIIX4State/rtc
> + hw/misc/auxbus.c: when creating an AUXBus
> + hw/misc/auxbus.c: when creating an AUXBus child
> + hw/misc/macio/macio.c: when initializing a MACIOState child
> + hw/misc/macio/macio.c: before realizing NewWorldMacIOState/pmu
> + hw/misc/macio/macio.c: before realizing NewWorldMacIOState/cuda
> + hw/net/virtio-net.c: Used for migration when using the failover
>                         mechanism to migration a vfio-pci/net. It is
>                         a no-op because at this point the device is
>                         already on the bus.
> + hw/pci-host/designware.c: before realizing DesignwarePCIEHost/root
> + hw/pci-host/gpex.c: before realizing GPEXHost/root
> + hw/pci-host/prep.c: when initializaing PREPPCIState/pci_dev

typo "initializing"

> + hw/pci-host/q35.c: before realizing Q35PCIHost/mch
> + hw/pci-host/versatile.c: when initializing PCIVPBState/pci_dev
> + hw/pci-host/xilinx-pcie.c: before realizing XilinxPCIEHost/root
> + hw/s390x/event-facility.c: when creating SCLPEventFacility/
>                               TYPE_SCLP_QUIESCE
> + hw/s390x/event-facility.c: ditto with SCLPEventFacility/
>                               TYPE_SCLP_CPU_HOTPLUG
> + hw/s390x/sclp.c: Not trivial because it is called on a SLCPDevice
>    just after realizing it. Ok because at this point the destination
>    bus (sysbus) is not in reset; the realize step is before the
>    machine reset.
> + hw/sd/core.c: Not OK. Used in sdbus_reparent_card(). See below.
> + hw/ssi/ssi.c: Used to put spi slave on spi bus and connect the cs
>    line in ssi_auto_connect_slave(). Ok because this function is only
>    used in realize step in hw/ssi/aspeed_smc.ci, hw/ssi/imx_spi.c,
>    hw/ssi/mss-spi.c, hw/ssi/xilinx_spi.c and hw/ssi/xilinx_spips.c.
> + hw/xen/xen-legacy-backend.c: when creating a XenLegacyDevice device
> + qdev-monitor.c: in device hotplug creation procedure before realize
> 
> Note that this commit alone will have no effect, right now there is no
> use of resettable API to reset anything. So a bus will never be tagged
> as in-reset by this same API.
> 
> The one place where side-effect will occurs is in hw/sd/core.c in
> sdbus_reparent_card(). This function is only used in the raspi machines,
> including during the sysbus reset procedure. This case will be
> carrefully handled when doing the multiple phase reset transition.
> 
> Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
> Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>

> ---
> 
> v6 update: there are now 3 more call sites (52 instead of 49).
> + hw/isa/piix4.c
> + hw/net/virtio-net.c
> + hw/virtio/vhost-user-fs-pci.c (in list below)
> 
> Exhaustive list of the 29 "virtio" caller to qdev_set_parent_bus():
> + hw/display/virtio-gpu-pci.c:     VirtIOGPUPCIBase/vgpu realize
> + hw/display/virtio-vga.c:         VirtIOVGABase/vgpu realize
> + hw/s390x/vhost-vsock-ccw.c:      VHostVSockCCWState/vdev realize
> + hw/s390x/virtio-ccw-9p.c:        V9fsCCWState/vdev realize
> + hw/s390x/virtio-ccw-balloon.c:   VirtIOBalloonCcw/vdev realize
> + hw/s390x/virtio-ccw-blk.c:       VirtIOBlkCcw/vdev realize
> + hw/s390x/virtio-ccw-crypto.c:    VirtIOCryptoCcw/vdev realize
> + hw/s390x/virtio-ccw-gpu.c:       VirtIOGPUCcw/vdev realize
> + hw/s390x/virtio-ccw-input.c:     VirtIOInputCcw/vdev realize
> + hw/s390x/virtio-ccw-net.c:       VirtIONetCcw/vdev realize
> + hw/s390x/virtio-ccw-rng.c:       VirtIORNGCcw/vdev realize
> + hw/s390x/virtio-ccw-scsi.c:      VirtIOSCSICcw/vdev realize
> + hw/s390x/virtio-ccw-scsi.c:      VHostSCSICcw/vdev realize
> + hw/s390x/virtio-ccw-serial.c:    VirtioSerialCcw/vdev realize
> + hw/virtio/vhost-scsi-pci.c:      VHostSCSIPCI/vdev realize
> + hw/virtio/vhost-user-blk-pci.c:  VHostUserBlkPCI/vdev realize
> + hw/virtio/vhost-user-fs-pci.c:   VHostUserFSPCI/vdev realize
> + hw/virtio/vhost-user-scsi-pci.c: VHostUserSCSIPCI/vdev realize
> + hw/virtio/vhost-vsock-pci.c:     VHostVSockPCI/vdev realize
> + hw/virtio/virtio-9p-pci.c:       V9fsPCIState/vdev realize
> + hw/virtio/virtio-balloon-pci.c:  VirtIOBalloonPCI/vdev realize
> + hw/virtio/virtio-blk-pci.c:      VirtIOBlkPCI/vdev realize
> + hw/virtio/virtio-crypto-pci.c:   VirtIOCryptoPCI/vdev realize
> + hw/virtio/virtio-input-pci.c:    VirtIOInputPCI/vdev realize
> + hw/virtio/virtio-net-pci.c:      VirtIONetPCI/vdev realize
> + hw/virtio/virtio-pmem-pci.c:     VirtIOPMEMPCI/vdev realize
> + hw/virtio/virtio-rng-pci.c:      VirtIORngPCI/vdev realize
> + hw/virtio/virtio-scsi-pci.c:     VirtIOSCSIPCI/vdev realize
> + hw/virtio/virtio-serial-pci.c:   VirtIOSerialPCI/vdev realize
> ---
>   hw/core/qdev.c | 16 +++++++++++-----
>   1 file changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/hw/core/qdev.c b/hw/core/qdev.c
> index d431a020fc..310b87e25a 100644
> --- a/hw/core/qdev.c
> +++ b/hw/core/qdev.c
> @@ -96,25 +96,31 @@ static void bus_add_child(BusState *bus, DeviceState *child)
>   
>   void qdev_set_parent_bus(DeviceState *dev, BusState *bus)
>   {
> -    bool replugging = dev->parent_bus != NULL;
> +    BusState *old_parent_bus = dev->parent_bus;
>   
> -    if (replugging) {
> +    if (old_parent_bus) {
>           trace_qdev_update_parent_bus(dev, object_get_typename(OBJECT(dev)),
> -            dev->parent_bus, object_get_typename(OBJECT(dev->parent_bus)),
> +            old_parent_bus, object_get_typename(OBJECT(old_parent_bus)),
>               OBJECT(bus), object_get_typename(OBJECT(bus)));
>           /*
>            * Keep a reference to the device while it's not plugged into
>            * any bus, to avoid it potentially evaporating when it is
>            * dereffed in bus_remove_child().
> +         * Also keep the ref of the parent bus until the end, so that
> +         * we can safely call resettable_change_parent() below.
>            */
>           object_ref(OBJECT(dev));
>           bus_remove_child(dev->parent_bus, dev);
> -        object_unref(OBJECT(dev->parent_bus));
>       }
>       dev->parent_bus = bus;
>       object_ref(OBJECT(bus));
>       bus_add_child(bus, dev);
> -    if (replugging) {
> +    if (dev->realized) {
> +        resettable_change_parent(OBJECT(dev), OBJECT(bus),
> +                                 OBJECT(old_parent_bus));
> +    }
> +    if (old_parent_bus) {
> +        object_unref(OBJECT(old_parent_bus));
>           object_unref(OBJECT(dev));
>       }
>   }
> 

Re: [PATCH v7 03/11] hw/core: create Resettable QOM interface

[Philippe Mathieu-Daudé]

On 1/16/20 2:59 AM, Philippe Mathieu-Daudé wrote:
> On 1/15/20 1:36 PM, Damien Hedde wrote:
>> This commit defines an interface allowing multi-phase reset. This aims
>> to solve a problem of the actual single-phase reset (built in
>> DeviceClass and BusClass): reset behavior is dependent on the order
>> in which reset handlers are called. In particular doing external
>> side-effect (like setting an qemu_irq) is problematic because receiving
>> object may not be reset yet.
>>
>> The Resettable interface divides the reset in 3 well defined phases.
>> To reset an object tree, all 1st phases are executed then all 2nd then
>> all 3rd. See the comments in include/hw/resettable.h for a more complete
>> description. The interface defines 3 phases to let the future
>> possibility of holding an object into reset for some time.
>>
>> The qdev/qbus reset in DeviceClass and BusClass will be modified in
>> following commits to use this interface. A mechanism is provided
>> to allow executing a transitional reset handler in place of the 2nd
>> phase which is executed in children-then-parent order inside a tree.
>> This will allow to transition devices and buses smoothly while
>> keeping the exact current qdev/qbus reset behavior for now.
>>
>> Documentation will be added in a following commit.
>>
>> Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
>> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
>> ---
>>
>> v7 update: un-nest struct ResettablePhases
>> ---
>>   Makefile.objs           |   1 +
>>   include/hw/resettable.h | 211 +++++++++++++++++++++++++++++++++++
>>   hw/core/resettable.c    | 238 ++++++++++++++++++++++++++++++++++++++++
>>   hw/core/Makefile.objs   |   1 +
>>   hw/core/trace-events    |  17 +++
>>   5 files changed, 468 insertions(+)
>>   create mode 100644 include/hw/resettable.h
>>   create mode 100644 hw/core/resettable.c
>>
>> diff --git a/Makefile.objs b/Makefile.objs
>> index 7c1e50f9d6..9752d549b4 100644
>> --- a/Makefile.objs
>> +++ b/Makefile.objs
>> @@ -191,6 +191,7 @@ trace-events-subdirs += migration
>>   trace-events-subdirs += net
>>   trace-events-subdirs += ui
>>   endif
>> +trace-events-subdirs += hw/core
> 
> TL;DR Duplicating this line breaks using the LTTng Userspace Tracer 
> library (UST backend).
> 
> Probably because you started this series before commit 26b8e6dc42b got 
> merged, Jun 13 2019!
> 
> Indeed Oct 02 2018...
> https://www.mail-archive.com/qemu-devel@nongnu.org/msg564153.html
> 
> The problem is you (correctly) sorted alphabetically while Alexey 
> appended at the end.
> 
>>   trace-events-subdirs += hw/display
>>   trace-events-subdirs += qapi
>>   trace-events-subdirs += qom
[...]
>> diff --git a/hw/core/trace-events b/hw/core/trace-events
>> index a375aa88a4..a2e43f1120 100644
>> --- a/hw/core/trace-events
>> +++ b/hw/core/trace-events
>> @@ -9,3 +9,20 @@ qbus_reset(void *obj, const char *objtype) "obj=%p(%s)"
>>   qbus_reset_all(void *obj, const char *objtype) "obj=%p(%s)"
>>   qbus_reset_tree(void *obj, const char *objtype) "obj=%p(%s)"
>>   qdev_update_parent_bus(void *obj, const char *objtype, void *oldp, 
>> const char *oldptype, void *newp, const char *newptype) "obj=%p(%s) 
>> old_parent=%p(%s) new_parent=%p(%s)"
>> +
>> +# resettable.c
>> +resettable_reset(void *obj, int cold) "obj=%p cold=%d"
>> +resettable_reset_assert_begin(void *obj, int cold) "obj=%p cold=%d"
>> +resettable_reset_assert_end(void *obj) "obj=%p"
>> +resettable_reset_release_begin(void *obj, int cold) "obj=%p cold=%d"
>> +resettable_reset_release_end(void *obj) "obj=%p"
>> +resettable_phase_enter_begin(void *obj, const char *objtype, uint32_t 
>> count, int type) "obj=%p(%s) count=%" PRIu32 " type=%d"
>> +resettable_phase_enter_exec(void *obj, const char *objtype, int type, 
>> int has_method) "obj=%p(%s) type=%d method=%d"
>> +resettable_phase_enter_end(void *obj, const char *objtype, uint32_t 
>> count) "obj=%p(%s) count=%" PRIu32
>> +resettable_phase_hold_begin(void *obj, const char *objtype, uint32_t 
>> count, int type) "obj=%p(%s) count=%" PRIu32 " type=%d"
>> +resettable_phase_hold_exec(void *obj, const char *objtype, int 
>> has_method) "obj=%p(%s) method=%d"
>> +resettable_phase_hold_end(void *obj, const char *objtype, uint32_t 
>> count) "obj=%p(%s) count=%" PRIu32
>> +resettable_phase_exit_begin(void *obj, const char *objtype, uint32_t 
>> count, int type) "obj=%p(%s) count=%" PRIu32 " type=%d"
>> +resettable_phase_exit_exec(void *obj, const char *objtype, int 
>> has_method) "obj=%p(%s) method=%d"
>> +resettable_phase_exit_end(void *obj, const char *objtype, uint32_t 
>> count) "obj=%p(%s) count=%" PRIu32
>> +resettable_transitional_function(void *obj, const char *objtype) 
>> "obj=%p(%s)"
> 
> Something here breaks ./configure --enable-trace-backends=ust:
> 
>    CC      trace-ust-all.o
> In file included from trace-ust-all.h:13,
>                   from trace-ust-all.c:13:
> trace-ust-all.h:35151:1: error: redefinition of 
> ‘__tracepoint_cb_qemu___loader_write_rom’
> 35151 | TRACEPOINT_EVENT(
>        | ^~~~~~~~~~~~~~~~
> trace-ust-all.h:31791:1: note: previous definition of 
> ‘__tracepoint_cb_qemu___loader_write_rom’ was here
> 31791 | TRACEPOINT_EVENT(
>        | ^~~~~~~~~~~~~~~~
> ...
> ./trace-ust-all.h:35388:1: error: redefinition of 
> ‘__tp_event_signature___qemu___resettable_transitional_function’
> 35388 | TRACEPOINT_EVENT(
>        | ^~~~~~~~~~~~~~~~
> ./trace-ust-all.h:32028:1: note: previous definition of 
> ‘__tp_event_signature___qemu___resettable_transitional_function’ was here
> 32028 | TRACEPOINT_EVENT(
>        | ^~~~~~~~~~~~~~~~
> In file included from /usr/include/lttng/tracepoint-event.h:58,
>                   from trace-ust-all.h:35401,
>                   from trace-ust-all.c:13:
> 
> Indeed:
> 
> 32028 TRACEPOINT_EVENT(
> 32029    qemu,
> 32030    resettable_transitional_function,
> 32031    TP_ARGS(void *, obj, const char *, objtype),
> 32032    TP_FIELDS(
> 32033        ctf_integer_hex(void *, obj, obj)
> 32034        ctf_string(objtype, objtype)
> 32035    )
> 32036 )
> 32037
> ...
> 35388 TRACEPOINT_EVENT(
> 35389    qemu,
> 35390    resettable_transitional_function,
> 35391    TP_ARGS(void *, obj, const char *, objtype),
> 35392    TP_FIELDS(
> 35393        ctf_integer_hex(void *, obj, obj)
> 35394        ctf_string(objtype, objtype)
> 35395    )
> 35396 )
> 35397
> 35398 #endif /* TRACE_ALL_GENERATED_UST_H */
> 
> Ah! I was going to say "no clue what could be wrong, so Cc'ing Stefan" 
> but got it:
> 
> $ git grep hw/core Makefile.objs
> Makefile.objs:194:trace-events-subdirs += hw/core
> Makefile.objs:207:trace-events-subdirs += hw/core
> 
> We might already have a 'uniq' makefile function to do:
> 
> trace-events-subdirs = $(call uniq $(trace-events-subdirs))
> 
> or maybe was it with $filter? I can't find it/remember, too tired.
> 
> So the fix is:
> 
> -- >8 --
> --- a/Makefile.objs
> +++ b/Makefile.objs
> @@ -191,7 +191,6 @@ trace-events-subdirs += migration
>   trace-events-subdirs += net
>   trace-events-subdirs += ui
>   endif
> -trace-events-subdirs += hw/core
>   trace-events-subdirs += hw/display
>   trace-events-subdirs += qapi
>   trace-events-subdirs += qom
> ---

Forgot to add, with trace-events-subdirs fixed:
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>

Re: [PATCH v7 03/11] hw/core: create Resettable QOM interface

[Damien Hedde]

On 1/16/20 2:59 AM, Philippe Mathieu-Daudé wrote:
> On 1/15/20 1:36 PM, Damien Hedde wrote:
>> This commit defines an interface allowing multi-phase reset. This aims
>> to solve a problem of the actual single-phase reset (built in
>> DeviceClass and BusClass): reset behavior is dependent on the order
>> in which reset handlers are called. In particular doing external
>> side-effect (like setting an qemu_irq) is problematic because receiving
>> object may not be reset yet.
>>
>> The Resettable interface divides the reset in 3 well defined phases.
>> To reset an object tree, all 1st phases are executed then all 2nd then
>> all 3rd. See the comments in include/hw/resettable.h for a more complete
>> description. The interface defines 3 phases to let the future
>> possibility of holding an object into reset for some time.
>>
>> The qdev/qbus reset in DeviceClass and BusClass will be modified in
>> following commits to use this interface. A mechanism is provided
>> to allow executing a transitional reset handler in place of the 2nd
>> phase which is executed in children-then-parent order inside a tree.
>> This will allow to transition devices and buses smoothly while
>> keeping the exact current qdev/qbus reset behavior for now.
>>
>> Documentation will be added in a following commit.
>>
>> Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
>> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
>> ---
>>
>> v7 update: un-nest struct ResettablePhases
>> ---
>>   Makefile.objs           |   1 +
>>   include/hw/resettable.h | 211 +++++++++++++++++++++++++++++++++++
>>   hw/core/resettable.c    | 238 ++++++++++++++++++++++++++++++++++++++++
>>   hw/core/Makefile.objs   |   1 +
>>   hw/core/trace-events    |  17 +++
>>   5 files changed, 468 insertions(+)
>>   create mode 100644 include/hw/resettable.h
>>   create mode 100644 hw/core/resettable.c
>>

> 
> Something here breaks ./configure --enable-trace-backends=ust:
> 
>   CC      trace-ust-all.o
> In file included from trace-ust-all.h:13,
>                  from trace-ust-all.c:13:
> trace-ust-all.h:35151:1: error: redefinition of
> ‘__tracepoint_cb_qemu___loader_write_rom’
> 35151 | TRACEPOINT_EVENT(
>       | ^~~~~~~~~~~~~~~~
> trace-ust-all.h:31791:1: note: previous definition of
> ‘__tracepoint_cb_qemu___loader_write_rom’ was here
> 31791 | TRACEPOINT_EVENT(
>       | ^~~~~~~~~~~~~~~~
> ...
> ./trace-ust-all.h:35388:1: error: redefinition of
> ‘__tp_event_signature___qemu___resettable_transitional_function’
> 35388 | TRACEPOINT_EVENT(
>       | ^~~~~~~~~~~~~~~~
> ./trace-ust-all.h:32028:1: note: previous definition of
> ‘__tp_event_signature___qemu___resettable_transitional_function’ was here
> 32028 | TRACEPOINT_EVENT(
>       | ^~~~~~~~~~~~~~~~
> In file included from /usr/include/lttng/tracepoint-event.h:58,
>                  from trace-ust-all.h:35401,
>                  from trace-ust-all.c:13:
> 
> Indeed:
> 
> 32028 TRACEPOINT_EVENT(
> 32029    qemu,
> 32030    resettable_transitional_function,
> 32031    TP_ARGS(void *, obj, const char *, objtype),
> 32032    TP_FIELDS(
> 32033        ctf_integer_hex(void *, obj, obj)
> 32034        ctf_string(objtype, objtype)
> 32035    )
> 32036 )
> 32037
> ...
> 35388 TRACEPOINT_EVENT(
> 35389    qemu,
> 35390    resettable_transitional_function,
> 35391    TP_ARGS(void *, obj, const char *, objtype),
> 35392    TP_FIELDS(
> 35393        ctf_integer_hex(void *, obj, obj)
> 35394        ctf_string(objtype, objtype)
> 35395    )
> 35396 )
> 35397
> 35398 #endif /* TRACE_ALL_GENERATED_UST_H */
> 
> Ah! I was going to say "no clue what could be wrong, so Cc'ing Stefan"
> but got it:
> 
> $ git grep hw/core Makefile.objs
> Makefile.objs:194:trace-events-subdirs += hw/core
> Makefile.objs:207:trace-events-subdirs += hw/core
> 
> We might already have a 'uniq' makefile function to do:
> 
> trace-events-subdirs = $(call uniq $(trace-events-subdirs))
> 
> or maybe was it with $filter? I can't find it/remember, too tired.

You can use $sort to remove duplicates in make.

> 
> So the fix is:
> 
> -- >8 --
> --- a/Makefile.objs
> +++ b/Makefile.objs
> @@ -191,7 +191,6 @@ trace-events-subdirs += migration
>  trace-events-subdirs += net
>  trace-events-subdirs += ui
>  endif
> -trace-events-subdirs += hw/core
>  trace-events-subdirs += hw/display
>  trace-events-subdirs += qapi
>  trace-events-subdirs += qom
> ---
> 

I'll remove the duplicate entry.
Thanks,

Damien

Re: [PATCH v7 10/11] vl: replace deprecated qbus_reset_all registration

[Damien Hedde]

On 1/16/20 12:44 AM, Philippe Mathieu-Daudé wrote:
> On 1/15/20 1:36 PM, Damien Hedde wrote:
>> Replace deprecated qbus_reset_all by resettable_cold_reset_fn for
>> the sysbus reset registration.
>>
>> Apart for the raspi machines, this does not impact the behavior
>> because:
>> + at this point resettable just calls the old reset methods of devices
>>    and buses in the same order as qdev/qbus.
>> + resettable handlers registered with qemu_register_reset are
>>    serialized; there is no interleaving.
>> + eventual explicit calls to legacy reset API (device_reset or
>>    qdev/qbus_reset) inside this reset handler will not be masked out
>>    by resettable mechanism; they do not go through resettable api.
>>
>> For the raspi machines, during the sysbus reset the sd-card is not
>> reset twice anymore but only once. This is a consequence of switching
>> both sysbus reset and changing parent to resettable; it detects the
>> second reset is not needed. This has no impact on the state after
>> reset; the sd-card reset method only reset local state and query
>> information from the block backend.
>>
>> Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
>> Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
>> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
>> ---
>>
>> The raspi reset change can be observed by using the following command
>> (reset will occurs, then do Ctrl-C to end qemu; no firmware is
>> given here).
>> qemu-system-aarch64 -M raspi3 \
>>      -trace resettable_phase_hold_exec \
>>      -trace qdev_update_parent_bus \
>>      -trace resettable_change_parent \
>>      -trace qdev_reset -trace qbus_reset
>>
>> Before the patch, the qdev/qbus_reset traces show when reset method are
>> called. After the patch, the resettable_phase_hold_exec show when reset
>> method are called.
>>
>> The traced reset order of the raspi3 is listed below. I've added empty
>> lines and the tree structure.
>>
>>   +->bcm2835-peripherals reset
>>   |
>>   |       +->sd-card reset
>>   |   +->sd-bus reset
>>   +->bcm2835_gpio reset
>>   |      -> dev_update_parent_bus (move the sd-card on the sdhci-bus)
>>   |      -> resettable_change_parent
>>   |
>>   +->bcm2835-dma reset
>>   |
>>   |   +->bcm2835-sdhost-bus reset
>>   +->bcm2835-sdhost reset
>>   |
>>   |       +->sd-card (reset ONLY BEFORE BEFORE THE PATCH)
>>   |   +->sdhci-bus reset
>>   +->generic-sdhci reset
>>   |
>>   +->bcm2835-rng reset
>>   +->bcm2835-property reset
>>   +->bcm2835-fb reset
>>   +->bcm2835-mbox reset
>>   +->bcm2835-aux reset
>>   +->pl011 reset
>>   +->bcm2835-ic reset
>>   +->bcm2836-control reset
>> System reset
>>
>> In both case, the sd-card is reset (being on bcm2835_gpio/sd-bus) then
>> moved
>> to generic-sdhci/sdhci-bus by the bcm2835_gpio reset method.
>>
>> Before the patch, it is then reset again being part of
>> generic-sdhci/sdhci-bus.
>> After the patch, it considered again for reset but its reset method is
>> not
>> called because it is already flagged as reset.
> 
> I find this information helpful, have you considered including it in the
> description?

I wasn't sure, I'll add it since I've to respin anyway to fix patch 3.

Thanks,
Damien

Re: [PATCH v7 03/11] hw/core: create Resettable QOM interface

[Philippe Mathieu-Daudé]

On 1/16/20 9:53 AM, Damien Hedde wrote:
> On 1/16/20 2:59 AM, Philippe Mathieu-Daudé wrote:
>> On 1/15/20 1:36 PM, Damien Hedde wrote:
>>> This commit defines an interface allowing multi-phase reset. This aims
>>> to solve a problem of the actual single-phase reset (built in
>>> DeviceClass and BusClass): reset behavior is dependent on the order
>>> in which reset handlers are called. In particular doing external
>>> side-effect (like setting an qemu_irq) is problematic because receiving
>>> object may not be reset yet.
>>>
>>> The Resettable interface divides the reset in 3 well defined phases.
>>> To reset an object tree, all 1st phases are executed then all 2nd then
>>> all 3rd. See the comments in include/hw/resettable.h for a more complete
>>> description. The interface defines 3 phases to let the future
>>> possibility of holding an object into reset for some time.
>>>
>>> The qdev/qbus reset in DeviceClass and BusClass will be modified in
>>> following commits to use this interface. A mechanism is provided
>>> to allow executing a transitional reset handler in place of the 2nd
>>> phase which is executed in children-then-parent order inside a tree.
>>> This will allow to transition devices and buses smoothly while
>>> keeping the exact current qdev/qbus reset behavior for now.
>>>
>>> Documentation will be added in a following commit.
>>>
>>> Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
>>> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
>>> ---
>>>
>>> v7 update: un-nest struct ResettablePhases
>>> ---
>>>    Makefile.objs           |   1 +
>>>    include/hw/resettable.h | 211 +++++++++++++++++++++++++++++++++++
>>>    hw/core/resettable.c    | 238 ++++++++++++++++++++++++++++++++++++++++
>>>    hw/core/Makefile.objs   |   1 +
>>>    hw/core/trace-events    |  17 +++
>>>    5 files changed, 468 insertions(+)
>>>    create mode 100644 include/hw/resettable.h
>>>    create mode 100644 hw/core/resettable.c
>>>
> 
>>
>> Something here breaks ./configure --enable-trace-backends=ust:
>>
>>    CC      trace-ust-all.o
>> In file included from trace-ust-all.h:13,
>>                   from trace-ust-all.c:13:
>> trace-ust-all.h:35151:1: error: redefinition of
>> ‘__tracepoint_cb_qemu___loader_write_rom’
>> 35151 | TRACEPOINT_EVENT(
>>        | ^~~~~~~~~~~~~~~~
>> trace-ust-all.h:31791:1: note: previous definition of
>> ‘__tracepoint_cb_qemu___loader_write_rom’ was here
>> 31791 | TRACEPOINT_EVENT(
>>        | ^~~~~~~~~~~~~~~~
>> ...
>> ./trace-ust-all.h:35388:1: error: redefinition of
>> ‘__tp_event_signature___qemu___resettable_transitional_function’
>> 35388 | TRACEPOINT_EVENT(
>>        | ^~~~~~~~~~~~~~~~
>> ./trace-ust-all.h:32028:1: note: previous definition of
>> ‘__tp_event_signature___qemu___resettable_transitional_function’ was here
>> 32028 | TRACEPOINT_EVENT(
>>        | ^~~~~~~~~~~~~~~~
>> In file included from /usr/include/lttng/tracepoint-event.h:58,
>>                   from trace-ust-all.h:35401,
>>                   from trace-ust-all.c:13:
>>
>> Indeed:
>>
>> 32028 TRACEPOINT_EVENT(
>> 32029    qemu,
>> 32030    resettable_transitional_function,
>> 32031    TP_ARGS(void *, obj, const char *, objtype),
>> 32032    TP_FIELDS(
>> 32033        ctf_integer_hex(void *, obj, obj)
>> 32034        ctf_string(objtype, objtype)
>> 32035    )
>> 32036 )
>> 32037
>> ...
>> 35388 TRACEPOINT_EVENT(
>> 35389    qemu,
>> 35390    resettable_transitional_function,
>> 35391    TP_ARGS(void *, obj, const char *, objtype),
>> 35392    TP_FIELDS(
>> 35393        ctf_integer_hex(void *, obj, obj)
>> 35394        ctf_string(objtype, objtype)
>> 35395    )
>> 35396 )
>> 35397
>> 35398 #endif /* TRACE_ALL_GENERATED_UST_H */
>>
>> Ah! I was going to say "no clue what could be wrong, so Cc'ing Stefan"
>> but got it:
>>
>> $ git grep hw/core Makefile.objs
>> Makefile.objs:194:trace-events-subdirs += hw/core
>> Makefile.objs:207:trace-events-subdirs += hw/core
>>
>> We might already have a 'uniq' makefile function to do:
>>
>> trace-events-subdirs = $(call uniq $(trace-events-subdirs))
>>
>> or maybe was it with $filter? I can't find it/remember, too tired.
> 
> You can use $sort to remove duplicates in make.

Ah $(sort ...) thanks, I was too tired to remember it =)

>>
>> So the fix is:
>>
>> -- >8 --
>> --- a/Makefile.objs
>> +++ b/Makefile.objs
>> @@ -191,7 +191,6 @@ trace-events-subdirs += migration
>>   trace-events-subdirs += net
>>   trace-events-subdirs += ui
>>   endif
>> -trace-events-subdirs += hw/core
>>   trace-events-subdirs += hw/display
>>   trace-events-subdirs += qapi
>>   trace-events-subdirs += qom
>> ---
>>
> 
> I'll remove the duplicate entry.

I prepared a patch to move hw/core, if qemu-trivial merges it first, you 
shouldn't need to respin your series.

Re: [PATCH v7 03/11] hw/core: create Resettable QOM interface

[Philippe Mathieu-Daudé]

On 1/15/20 1:36 PM, Damien Hedde wrote:
> This commit defines an interface allowing multi-phase reset. This aims
> to solve a problem of the actual single-phase reset (built in
> DeviceClass and BusClass): reset behavior is dependent on the order
> in which reset handlers are called. In particular doing external
> side-effect (like setting an qemu_irq) is problematic because receiving
> object may not be reset yet.
> 
> The Resettable interface divides the reset in 3 well defined phases.
> To reset an object tree, all 1st phases are executed then all 2nd then
> all 3rd. See the comments in include/hw/resettable.h for a more complete
> description. The interface defines 3 phases to let the future
> possibility of holding an object into reset for some time.
> 
> The qdev/qbus reset in DeviceClass and BusClass will be modified in
> following commits to use this interface. A mechanism is provided
> to allow executing a transitional reset handler in place of the 2nd
> phase which is executed in children-then-parent order inside a tree.
> This will allow to transition devices and buses smoothly while
> keeping the exact current qdev/qbus reset behavior for now.
> 
> Documentation will be added in a following commit.
> 
> Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
> ---
> 
> v7 update: un-nest struct ResettablePhases
> ---
>   Makefile.objs           |   1 +
>   include/hw/resettable.h | 211 +++++++++++++++++++++++++++++++++++
>   hw/core/resettable.c    | 238 ++++++++++++++++++++++++++++++++++++++++
>   hw/core/Makefile.objs   |   1 +
>   hw/core/trace-events    |  17 +++
>   5 files changed, 468 insertions(+)
>   create mode 100644 include/hw/resettable.h
>   create mode 100644 hw/core/resettable.c
> 
> diff --git a/Makefile.objs b/Makefile.objs
> index 7c1e50f9d6..9752d549b4 100644
> --- a/Makefile.objs
> +++ b/Makefile.objs
> @@ -191,6 +191,7 @@ trace-events-subdirs += migration
>   trace-events-subdirs += net
>   trace-events-subdirs += ui
>   endif
> +trace-events-subdirs += hw/core
>   trace-events-subdirs += hw/display
>   trace-events-subdirs += qapi
>   trace-events-subdirs += qom
> diff --git a/include/hw/resettable.h b/include/hw/resettable.h
> new file mode 100644
> index 0000000000..58b3df4c22
> --- /dev/null
> +++ b/include/hw/resettable.h
> @@ -0,0 +1,211 @@
> +/*
> + * Resettable interface header.
> + *
> + * Copyright (c) 2019 GreenSocs SAS
> + *
> + * Authors:
> + *   Damien Hedde
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#ifndef HW_RESETTABLE_H
> +#define HW_RESETTABLE_H
> +
> +#include "qom/object.h"
> +
> +#define TYPE_RESETTABLE_INTERFACE "resettable"
> +
> +#define RESETTABLE_CLASS(class) \
> +    OBJECT_CLASS_CHECK(ResettableClass, (class), TYPE_RESETTABLE_INTERFACE)
> +
> +#define RESETTABLE_GET_CLASS(obj) \
> +    OBJECT_GET_CLASS(ResettableClass, (obj), TYPE_RESETTABLE_INTERFACE)
> +
> +typedef struct ResettableState ResettableState;
> +
> +/**
> + * ResetType:
> + * Types of reset.
> + *
> + * + Cold: reset resulting from a power cycle of the object.
> + *
> + * TODO: Support has to be added to handle more types. In particular,
> + * ResettableState structure needs to be expanded.
> + */
> +typedef enum ResetType {
> +    RESET_TYPE_COLD,
> +} ResetType;
> +
> +/*
> + * ResettableClass:
> + * Interface for resettable objects.
> + *
> + * See docs/devel/reset.rst for more detailed information about how QEMU models
> + * reset. This whole API must only be used when holding the iothread mutex.
> + *
> + * All objects which can be reset must implement this interface;
> + * it is usually provided by a base class such as DeviceClass or BusClass.
> + * Every Resettable object must maintain some state tracking the
> + * progress of a reset operation by providing a ResettableState structure.
> + * The functions defined in this module take care of updating the
> + * state of the reset.
> + * The base class implementation of the interface provides this
> + * state and implements the associated method: get_state.
> + *
> + * Concrete object implementations (typically specific devices
> + * such as a UART model) should provide the functions
> + * for the phases.enter, phases.hold and phases.exit methods, which
> + * they can set in their class init function, either directly or
> + * by calling resettable_class_set_parent_phases().
> + * The phase methods are guaranteed to only only ever be called once
> + * for any reset event, in the order 'enter', 'hold', 'exit'.
> + * An object will always move quickly from 'enter' to 'hold'
> + * but might remain in 'hold' for an arbitrary period of time
> + * before eventually reset is deasserted and the 'exit' phase is called.
> + * Object implementations should be prepared for functions handling
> + * inbound connections from other devices (such as qemu_irq handler
> + * functions) to be called at any point during reset after their
> + * 'enter' method has been called.
> + *
> + * Users of a resettable object should not call these methods
> + * directly, but instead use the function resettable_reset().
> + *
> + * @phases.enter: This phase is called when the object enters reset. It
> + * should reset local state of the object, but it must not do anything that
> + * has a side-effect on other objects, such as raising or lowering a qemu_irq
> + * line or reading or writing guest memory. It takes the reset's type as
> + * argument.
> + *
> + * @phases.hold: This phase is called for entry into reset, once every object
> + * in the system which is being reset has had its @phases.enter method called.
> + * At this point devices can do actions that affect other objects.
> + *
> + * @phases.exit: This phase is called when the object leaves the reset state.
> + * Actions affecting other objects are permitted.
> + *
> + * @get_state: Mandatory method which must return a pointer to a
> + * ResettableState.
> + *
> + * @get_transitional_function: transitional method to handle Resettable objects
> + * not yet fully moved to this interface. It will be removed as soon as it is
> + * not needed anymore. This method is optional and may return a pointer to a
> + * function to be used instead of the phases. If the method exists and returns
> + * a non-NULL function pointer then that function is executed as a replacement
> + * of the 'hold' phase method taking the object as argument. The two other phase
> + * methods are not executed.
> + *
> + * @child_foreach: Executes a given callback on every Resettable child. Child
> + * in this context means a child in the qbus tree, so the children of a qbus
> + * are the devices on it, and the children of a device are all the buses it
> + * owns. This is not the same as the QOM object hierarchy. The function takes
> + * additional opaque and ResetType arguments which must be passed unmodified to
> + * the callback.
> + */
> +typedef void (*ResettableEnterPhase)(Object *obj, ResetType type);
> +typedef void (*ResettableHoldPhase)(Object *obj);
> +typedef void (*ResettableExitPhase)(Object *obj);
> +typedef ResettableState * (*ResettableGetState)(Object *obj);
> +typedef void (*ResettableTrFunction)(Object *obj);
> +typedef ResettableTrFunction (*ResettableGetTrFunction)(Object *obj);
> +typedef void (*ResettableChildCallback)(Object *, void *opaque,
> +                                        ResetType type);
> +typedef void (*ResettableChildForeach)(Object *obj,
> +                                       ResettableChildCallback cb,
> +                                       void *opaque, ResetType type);
> +typedef struct ResettablePhases {
> +    ResettableEnterPhase enter;
> +    ResettableHoldPhase hold;
> +    ResettableExitPhase exit;
> +} ResettablePhases;
> +typedef struct ResettableClass {
> +    InterfaceClass parent_class;
> +
> +    /* Phase methods */
> +    ResettablePhases phases;
> +
> +    /* State access method */
> +    ResettableGetState get_state;
> +
> +    /* Transitional method for legacy reset compatibility */
> +    ResettableGetTrFunction get_transitional_function;
> +
> +    /* Hierarchy handling method */
> +    ResettableChildForeach child_foreach;
> +} ResettableClass;
> +
> +/**
> + * ResettableState:
> + * Structure holding reset related state. The fields should not be accessed
> + * directly; the definition is here to allow further inclusion into other
> + * objects.
> + *
> + * @count: Number of reset level the object is into. It is incremented when
> + * the reset operation starts and decremented when it finishes.
> + * @hold_phase_pending: flag which indicates that we need to invoke the 'hold'
> + * phase handler for this object.
> + * @exit_phase_in_progress: true if we are currently in the exit phase
> + */
> +struct ResettableState {
> +    uint32_t count;
> +    bool hold_phase_pending;
> +    bool exit_phase_in_progress;
> +};
> +
> +/**
> + * resettable_reset:
> + * Trigger a reset on an object @obj of type @type. @obj must implement
> + * Resettable interface.
> + *
> + * Calling this function is equivalent to calling @resettable_assert_reset()
> + * then @resettable_release_reset().
> + */
> +void resettable_reset(Object *obj, ResetType type);
> +
> +/**
> + * resettable_assert_reset:
> + * Put an object @obj into reset. @obj must implement Resettable interface.
> + *
> + * @resettable_release_reset() must eventually be called after this call.
> + * There must be one call to @resettable_release_reset() per call of
> + * @resettable_assert_reset(), with the same type argument.
> + *
> + * NOTE: Until support for migration is added, the @resettable_release_reset()
> + * must not be delayed. It must occur just after @resettable_assert_reset() so
> + * that migration cannot be triggered in between. Prefer using
> + * @resettable_reset() for now.
> + */
> +void resettable_assert_reset(Object *obj, ResetType type);
> +
> +/**
> + * resettable_release_reset:
> + * Release the object @obj from reset. @obj must implement Resettable interface.
> + *
> + * See @resettable_assert_reset() description for details.
> + */
> +void resettable_release_reset(Object *obj, ResetType type);
> +
> +/**
> + * resettable_is_in_reset:
> + * Return true if @obj is under reset.
> + *
> + * @obj must implement Resettable interface.
> + */
> +bool resettable_is_in_reset(Object *obj);
> +
> +/**
> + * resettable_class_set_parent_phases:
> + *
> + * Save @rc current reset phases into @parent_phases and override @rc phases
> + * by the given new methods (@enter, @hold and @exit).
> + * Each phase is overridden only if the new one is not NULL allowing to
> + * override a subset of phases.
> + */
> +void resettable_class_set_parent_phases(ResettableClass *rc,
> +                                        ResettableEnterPhase enter,
> +                                        ResettableHoldPhase hold,
> +                                        ResettableExitPhase exit,
> +                                        ResettablePhases *parent_phases);
> +
> +#endif
> diff --git a/hw/core/resettable.c b/hw/core/resettable.c
> new file mode 100644
> index 0000000000..9133208487
> --- /dev/null
> +++ b/hw/core/resettable.c
> @@ -0,0 +1,238 @@
> +/*
> + * Resettable interface.
> + *
> + * Copyright (c) 2019 GreenSocs SAS
> + *
> + * Authors:
> + *   Damien Hedde
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qemu/module.h"
> +#include "hw/resettable.h"
> +#include "trace.h"
> +
> +/**
> + * resettable_phase_enter/hold/exit:
> + * Function executing a phase recursively in a resettable object and its
> + * children.
> + */
> +static void resettable_phase_enter(Object *obj, void *opaque, ResetType type);
> +static void resettable_phase_hold(Object *obj, void *opaque, ResetType type);
> +static void resettable_phase_exit(Object *obj, void *opaque, ResetType type);
> +
> +/**
> + * enter_phase_in_progress:
> + * True if we are currently in reset enter phase.
> + *
> + * Note: This flag is only used to guarantee (using asserts) that the reset
> + * API is used correctly. We can use a global variable because we rely on the
> + * iothread mutex to ensure only one reset operation is in a progress at a
> + * given time.
> + */
> +static bool enter_phase_in_progress;
> +
> +void resettable_reset(Object *obj, ResetType type)
> +{
> +    trace_resettable_reset(obj, type);
> +    resettable_assert_reset(obj, type);
> +    resettable_release_reset(obj, type);
> +}
> +
> +void resettable_assert_reset(Object *obj, ResetType type)
> +{
> +    /* TODO: change this assert when adding support for other reset types */
> +    assert(type == RESET_TYPE_COLD);
> +    trace_resettable_reset_assert_begin(obj, type);
> +    assert(!enter_phase_in_progress);
> +
> +    enter_phase_in_progress = true;
> +    resettable_phase_enter(obj, NULL, type);
> +    enter_phase_in_progress = false;
> +
> +    resettable_phase_hold(obj, NULL, type);
> +
> +    trace_resettable_reset_assert_end(obj);
> +}
> +
> +void resettable_release_reset(Object *obj, ResetType type)
> +{
> +    /* TODO: change this assert when adding support for other reset types */
> +    assert(type == RESET_TYPE_COLD);
> +    trace_resettable_reset_release_begin(obj, type);
> +    assert(!enter_phase_in_progress);
> +
> +    resettable_phase_exit(obj, NULL, type);
> +
> +    trace_resettable_reset_release_end(obj);
> +}
> +
> +bool resettable_is_in_reset(Object *obj)
> +{
> +    ResettableClass *rc = RESETTABLE_GET_CLASS(obj);
> +    ResettableState *s = rc->get_state(obj);
> +
> +    return s->count > 0;
> +}
> +
> +/**
> + * resettable_child_foreach:
> + * helper to avoid checking the existence of the method.
> + */
> +static void resettable_child_foreach(ResettableClass *rc, Object *obj,
> +                                     ResettableChildCallback cb,
> +                                     void *opaque, ResetType type)
> +{
> +    if (rc->child_foreach) {
> +        rc->child_foreach(obj, cb, opaque, type);
> +    }
> +}
> +
> +/**
> + * resettable_get_tr_func:
> + * helper to fetch transitional reset callback if any.
> + */
> +static ResettableTrFunction resettable_get_tr_func(ResettableClass *rc,
> +                                                   Object *obj)
> +{
> +    ResettableTrFunction tr_func = NULL;
> +    if (rc->get_transitional_function) {
> +        tr_func = rc->get_transitional_function(obj);
> +    }
> +    return tr_func;
> +}
> +
> +static void resettable_phase_enter(Object *obj, void *opaque, ResetType type)
> +{
> +    ResettableClass *rc = RESETTABLE_GET_CLASS(obj);
> +    ResettableState *s = rc->get_state(obj);
> +    const char *obj_typename = object_get_typename(obj);
> +    bool action_needed = false;
> +
> +    /* exit phase has to finish properly before entering back in reset */
> +    assert(!s->exit_phase_in_progress);
> +
> +    trace_resettable_phase_enter_begin(obj, obj_typename, s->count, type);
> +
> +    /* Only take action if we really enter reset for the 1st time. */
> +    /*
> +     * TODO: if adding more ResetType support, some additional checks
> +     * are probably needed here.
> +     */
> +    if (s->count++ == 0) {
> +        action_needed = true;
> +    }
> +    /*
> +     * We limit the count to an arbitrary "big" value. The value is big
> +     * enough not to be triggered normally.
> +     * The assert will stop an infinite loop if there is a cycle in the
> +     * reset tree. The loop goes through resettable_foreach_child below
> +     * which at some point will call us again.
> +     */
> +    assert(s->count <= 50);
> +
> +    /*
> +     * handle the children even if action_needed is at false so that
> +     * child counts are incremented too
> +     */
> +    resettable_child_foreach(rc, obj, resettable_phase_enter, NULL, type);
> +
> +    /* execute enter phase for the object if needed */
> +    if (action_needed) {
> +        trace_resettable_phase_enter_exec(obj, obj_typename, type,
> +                                          !!rc->phases.enter);
> +        if (rc->phases.enter && !resettable_get_tr_func(rc, obj)) {
> +            rc->phases.enter(obj, type);
> +        }
> +        s->hold_phase_pending = true;
> +    }
> +    trace_resettable_phase_enter_end(obj, obj_typename, s->count);
> +}
> +
> +static void resettable_phase_hold(Object *obj, void *opaque, ResetType type)
> +{
> +    ResettableClass *rc = RESETTABLE_GET_CLASS(obj);
> +    ResettableState *s = rc->get_state(obj);
> +    const char *obj_typename = object_get_typename(obj);
> +
> +    /* exit phase has to finish properly before entering back in reset */
> +    assert(!s->exit_phase_in_progress);
> +
> +    trace_resettable_phase_hold_begin(obj, obj_typename, s->count, type);
> +
> +    /* handle children first */
> +    resettable_child_foreach(rc, obj, resettable_phase_hold, NULL, type);
> +
> +    /* exec hold phase */
> +    if (s->hold_phase_pending) {
> +        s->hold_phase_pending = false;
> +        ResettableTrFunction tr_func = resettable_get_tr_func(rc, obj);
> +        trace_resettable_phase_hold_exec(obj, obj_typename, !!rc->phases.hold);
> +        if (tr_func) {
> +            trace_resettable_transitional_function(obj, obj_typename);
> +            tr_func(obj);
> +        } else if (rc->phases.hold) {
> +            rc->phases.hold(obj);
> +        }
> +    }
> +    trace_resettable_phase_hold_end(obj, obj_typename, s->count);
> +}
> +
> +static void resettable_phase_exit(Object *obj, void *opaque, ResetType type)
> +{
> +    ResettableClass *rc = RESETTABLE_GET_CLASS(obj);
> +    ResettableState *s = rc->get_state(obj);
> +    const char *obj_typename = object_get_typename(obj);
> +
> +    assert(!s->exit_phase_in_progress);
> +    trace_resettable_phase_exit_begin(obj, obj_typename, s->count, type);
> +
> +    /* exit_phase_in_progress ensures this phase is 'atomic' */
> +    s->exit_phase_in_progress = true;
> +    resettable_child_foreach(rc, obj, resettable_phase_exit, NULL, type);
> +
> +    assert(s->count > 0);
> +    if (s->count == 1) {
> +        trace_resettable_phase_exit_exec(obj, obj_typename, !!rc->phases.exit);
> +        if (rc->phases.exit && !resettable_get_tr_func(rc, obj)) {
> +            rc->phases.exit(obj);
> +        }
> +        s->count = 0;
> +    }
> +    s->exit_phase_in_progress = false;
> +    trace_resettable_phase_exit_end(obj, obj_typename, s->count);
> +}
> +
> +void resettable_class_set_parent_phases(ResettableClass *rc,
> +                                        ResettableEnterPhase enter,
> +                                        ResettableHoldPhase hold,
> +                                        ResettableExitPhase exit,
> +                                        ResettablePhases *parent_phases)
> +{
> +    *parent_phases = rc->phases;
> +    if (enter) {

Why care about checking if handlers are not NULL? It is not like you are 
overwriting a pointer previously set.

Anyway:
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>

> +        rc->phases.enter = enter;
> +    }
> +    if (hold) {
> +        rc->phases.hold = hold;
> +    }
> +    if (exit) {
> +        rc->phases.exit = exit;
> +    }
> +}
> +
> +static const TypeInfo resettable_interface_info = {
> +    .name       = TYPE_RESETTABLE_INTERFACE,
> +    .parent     = TYPE_INTERFACE,
> +    .class_size = sizeof(ResettableClass),
> +};
> +
> +static void reset_register_types(void)
> +{
> +    type_register_static(&resettable_interface_info);
> +}
> +
> +type_init(reset_register_types)
> diff --git a/hw/core/Makefile.objs b/hw/core/Makefile.objs
> index 0edd9e635d..1709a122d4 100644
> --- a/hw/core/Makefile.objs
> +++ b/hw/core/Makefile.objs
> @@ -1,6 +1,7 @@
>   # core qdev-related obj files, also used by *-user:
>   common-obj-y += qdev.o qdev-properties.o
>   common-obj-y += bus.o reset.o
> +common-obj-y += resettable.o
>   common-obj-$(CONFIG_SOFTMMU) += qdev-fw.o
>   common-obj-$(CONFIG_SOFTMMU) += fw-path-provider.o
>   # irq.o needed for qdev GPIO handling:
> diff --git a/hw/core/trace-events b/hw/core/trace-events
> index a375aa88a4..a2e43f1120 100644
> --- a/hw/core/trace-events
> +++ b/hw/core/trace-events
> @@ -9,3 +9,20 @@ qbus_reset(void *obj, const char *objtype) "obj=%p(%s)"
>   qbus_reset_all(void *obj, const char *objtype) "obj=%p(%s)"
>   qbus_reset_tree(void *obj, const char *objtype) "obj=%p(%s)"
>   qdev_update_parent_bus(void *obj, const char *objtype, void *oldp, const char *oldptype, void *newp, const char *newptype) "obj=%p(%s) old_parent=%p(%s) new_parent=%p(%s)"
> +
> +# resettable.c
> +resettable_reset(void *obj, int cold) "obj=%p cold=%d"
> +resettable_reset_assert_begin(void *obj, int cold) "obj=%p cold=%d"
> +resettable_reset_assert_end(void *obj) "obj=%p"
> +resettable_reset_release_begin(void *obj, int cold) "obj=%p cold=%d"
> +resettable_reset_release_end(void *obj) "obj=%p"
> +resettable_phase_enter_begin(void *obj, const char *objtype, uint32_t count, int type) "obj=%p(%s) count=%" PRIu32 " type=%d"
> +resettable_phase_enter_exec(void *obj, const char *objtype, int type, int has_method) "obj=%p(%s) type=%d method=%d"
> +resettable_phase_enter_end(void *obj, const char *objtype, uint32_t count) "obj=%p(%s) count=%" PRIu32
> +resettable_phase_hold_begin(void *obj, const char *objtype, uint32_t count, int type) "obj=%p(%s) count=%" PRIu32 " type=%d"
> +resettable_phase_hold_exec(void *obj, const char *objtype, int has_method) "obj=%p(%s) method=%d"
> +resettable_phase_hold_end(void *obj, const char *objtype, uint32_t count) "obj=%p(%s) count=%" PRIu32
> +resettable_phase_exit_begin(void *obj, const char *objtype, uint32_t count, int type) "obj=%p(%s) count=%" PRIu32 " type=%d"
> +resettable_phase_exit_exec(void *obj, const char *objtype, int has_method) "obj=%p(%s) method=%d"
> +resettable_phase_exit_end(void *obj, const char *objtype, uint32_t count) "obj=%p(%s) count=%" PRIu32
> +resettable_transitional_function(void *obj, const char *objtype) "obj=%p(%s)"
> 

Re: [PATCH v7 03/11] hw/core: create Resettable QOM interface

[Philippe Mathieu-Daudé]

On 1/15/20 1:36 PM, Damien Hedde wrote:
> This commit defines an interface allowing multi-phase reset. This aims
> to solve a problem of the actual single-phase reset (built in
> DeviceClass and BusClass): reset behavior is dependent on the order
> in which reset handlers are called. In particular doing external
> side-effect (like setting an qemu_irq) is problematic because receiving
> object may not be reset yet.
> 
> The Resettable interface divides the reset in 3 well defined phases.
> To reset an object tree, all 1st phases are executed then all 2nd then
> all 3rd. See the comments in include/hw/resettable.h for a more complete
> description. The interface defines 3 phases to let the future
> possibility of holding an object into reset for some time.
> 
> The qdev/qbus reset in DeviceClass and BusClass will be modified in
> following commits to use this interface. A mechanism is provided
> to allow executing a transitional reset handler in place of the 2nd
> phase which is executed in children-then-parent order inside a tree.
> This will allow to transition devices and buses smoothly while
> keeping the exact current qdev/qbus reset behavior for now.
> 
> Documentation will be added in a following commit.
> 
> Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
> ---
> 
> v7 update: un-nest struct ResettablePhases
> ---
>   Makefile.objs           |   1 +
>   include/hw/resettable.h | 211 +++++++++++++++++++++++++++++++++++
>   hw/core/resettable.c    | 238 ++++++++++++++++++++++++++++++++++++++++
>   hw/core/Makefile.objs   |   1 +
>   hw/core/trace-events    |  17 +++
>   5 files changed, 468 insertions(+)
>   create mode 100644 include/hw/resettable.h
>   create mode 100644 hw/core/resettable.c
> 
> diff --git a/Makefile.objs b/Makefile.objs
> index 7c1e50f9d6..9752d549b4 100644
> --- a/Makefile.objs
> +++ b/Makefile.objs
> @@ -191,6 +191,7 @@ trace-events-subdirs += migration
>   trace-events-subdirs += net
>   trace-events-subdirs += ui
>   endif
> +trace-events-subdirs += hw/core
>   trace-events-subdirs += hw/display
>   trace-events-subdirs += qapi
>   trace-events-subdirs += qom
> diff --git a/include/hw/resettable.h b/include/hw/resettable.h
> new file mode 100644
> index 0000000000..58b3df4c22
> --- /dev/null
> +++ b/include/hw/resettable.h
> @@ -0,0 +1,211 @@
> +/*
> + * Resettable interface header.
> + *
> + * Copyright (c) 2019 GreenSocs SAS
> + *
> + * Authors:
> + *   Damien Hedde
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#ifndef HW_RESETTABLE_H
> +#define HW_RESETTABLE_H
> +
> +#include "qom/object.h"
> +
> +#define TYPE_RESETTABLE_INTERFACE "resettable"
> +
> +#define RESETTABLE_CLASS(class) \
> +    OBJECT_CLASS_CHECK(ResettableClass, (class), TYPE_RESETTABLE_INTERFACE)
> +
> +#define RESETTABLE_GET_CLASS(obj) \
> +    OBJECT_GET_CLASS(ResettableClass, (obj), TYPE_RESETTABLE_INTERFACE)
> +
> +typedef struct ResettableState ResettableState;
> +
> +/**
> + * ResetType:
> + * Types of reset.
> + *
> + * + Cold: reset resulting from a power cycle of the object.
> + *
> + * TODO: Support has to be added to handle more types. In particular,
> + * ResettableState structure needs to be expanded.
> + */
> +typedef enum ResetType {
> +    RESET_TYPE_COLD,
> +} ResetType;
> +
> +/*
> + * ResettableClass:
> + * Interface for resettable objects.
> + *
> + * See docs/devel/reset.rst for more detailed information about how QEMU models
> + * reset. This whole API must only be used when holding the iothread mutex.
> + *
> + * All objects which can be reset must implement this interface;
> + * it is usually provided by a base class such as DeviceClass or BusClass.
> + * Every Resettable object must maintain some state tracking the
> + * progress of a reset operation by providing a ResettableState structure.
> + * The functions defined in this module take care of updating the
> + * state of the reset.
> + * The base class implementation of the interface provides this
> + * state and implements the associated method: get_state.
> + *
> + * Concrete object implementations (typically specific devices
> + * such as a UART model) should provide the functions
> + * for the phases.enter, phases.hold and phases.exit methods, which
> + * they can set in their class init function, either directly or
> + * by calling resettable_class_set_parent_phases().
> + * The phase methods are guaranteed to only only ever be called once
> + * for any reset event, in the order 'enter', 'hold', 'exit'.
> + * An object will always move quickly from 'enter' to 'hold'
> + * but might remain in 'hold' for an arbitrary period of time
> + * before eventually reset is deasserted and the 'exit' phase is called.
> + * Object implementations should be prepared for functions handling
> + * inbound connections from other devices (such as qemu_irq handler
> + * functions) to be called at any point during reset after their
> + * 'enter' method has been called.
> + *
> + * Users of a resettable object should not call these methods
> + * directly, but instead use the function resettable_reset().
> + *
> + * @phases.enter: This phase is called when the object enters reset. It
> + * should reset local state of the object, but it must not do anything that
> + * has a side-effect on other objects, such as raising or lowering a qemu_irq
> + * line or reading or writing guest memory. It takes the reset's type as
> + * argument.
> + *
> + * @phases.hold: This phase is called for entry into reset, once every object
> + * in the system which is being reset has had its @phases.enter method called.
> + * At this point devices can do actions that affect other objects.
> + *
> + * @phases.exit: This phase is called when the object leaves the reset state.
> + * Actions affecting other objects are permitted.
> + *
> + * @get_state: Mandatory method which must return a pointer to a
> + * ResettableState.
> + *
> + * @get_transitional_function: transitional method to handle Resettable objects
> + * not yet fully moved to this interface. It will be removed as soon as it is
> + * not needed anymore. This method is optional and may return a pointer to a
> + * function to be used instead of the phases. If the method exists and returns
> + * a non-NULL function pointer then that function is executed as a replacement
> + * of the 'hold' phase method taking the object as argument. The two other phase
> + * methods are not executed.
> + *
> + * @child_foreach: Executes a given callback on every Resettable child. Child
> + * in this context means a child in the qbus tree, so the children of a qbus
> + * are the devices on it, and the children of a device are all the buses it
> + * owns. This is not the same as the QOM object hierarchy. The function takes
> + * additional opaque and ResetType arguments which must be passed unmodified to
> + * the callback.
> + */
> +typedef void (*ResettableEnterPhase)(Object *obj, ResetType type);
> +typedef void (*ResettableHoldPhase)(Object *obj);
> +typedef void (*ResettableExitPhase)(Object *obj);
> +typedef ResettableState * (*ResettableGetState)(Object *obj);
> +typedef void (*ResettableTrFunction)(Object *obj);
> +typedef ResettableTrFunction (*ResettableGetTrFunction)(Object *obj);
> +typedef void (*ResettableChildCallback)(Object *, void *opaque,
> +                                        ResetType type);
> +typedef void (*ResettableChildForeach)(Object *obj,
> +                                       ResettableChildCallback cb,
> +                                       void *opaque, ResetType type);
> +typedef struct ResettablePhases {
> +    ResettableEnterPhase enter;
> +    ResettableHoldPhase hold;
> +    ResettableExitPhase exit;
> +} ResettablePhases;
> +typedef struct ResettableClass {
> +    InterfaceClass parent_class;
> +
> +    /* Phase methods */
> +    ResettablePhases phases;
> +
> +    /* State access method */
> +    ResettableGetState get_state;
> +
> +    /* Transitional method for legacy reset compatibility */
> +    ResettableGetTrFunction get_transitional_function;
> +
> +    /* Hierarchy handling method */
> +    ResettableChildForeach child_foreach;
> +} ResettableClass;
> +
> +/**
> + * ResettableState:
> + * Structure holding reset related state. The fields should not be accessed
> + * directly; the definition is here to allow further inclusion into other
> + * objects.
> + *
> + * @count: Number of reset level the object is into. It is incremented when
> + * the reset operation starts and decremented when it finishes.

Maybe you can add this comment and the variable in patch 5/11, that 
would make patch 5 easier to review.

> + * @hold_phase_pending: flag which indicates that we need to invoke the 'hold'
> + * phase handler for this object.
> + * @exit_phase_in_progress: true if we are currently in the exit phase
> + */
> +struct ResettableState {
> +    uint32_t count;

Maybe simply 'unsigned'?

> +    bool hold_phase_pending;
> +    bool exit_phase_in_progress;
> +};
> +
> +/**
> + * resettable_reset:
> + * Trigger a reset on an object @obj of type @type. @obj must implement
> + * Resettable interface.
> + *
> + * Calling this function is equivalent to calling @resettable_assert_reset()
> + * then @resettable_release_reset().
> + */
> +void resettable_reset(Object *obj, ResetType type);
> +
> +/**
> + * resettable_assert_reset:
> + * Put an object @obj into reset. @obj must implement Resettable interface.
> + *
> + * @resettable_release_reset() must eventually be called after this call.
> + * There must be one call to @resettable_release_reset() per call of
> + * @resettable_assert_reset(), with the same type argument.
> + *
> + * NOTE: Until support for migration is added, the @resettable_release_reset()
> + * must not be delayed. It must occur just after @resettable_assert_reset() so
> + * that migration cannot be triggered in between. Prefer using
> + * @resettable_reset() for now.
> + */
> +void resettable_assert_reset(Object *obj, ResetType type);
> +
> +/**
> + * resettable_release_reset:
> + * Release the object @obj from reset. @obj must implement Resettable interface.
> + *
> + * See @resettable_assert_reset() description for details.
> + */
> +void resettable_release_reset(Object *obj, ResetType type);
> +
> +/**
> + * resettable_is_in_reset:
> + * Return true if @obj is under reset.
> + *
> + * @obj must implement Resettable interface.
> + */
> +bool resettable_is_in_reset(Object *obj);
> +
> +/**
> + * resettable_class_set_parent_phases:
> + *
> + * Save @rc current reset phases into @parent_phases and override @rc phases
> + * by the given new methods (@enter, @hold and @exit).
> + * Each phase is overridden only if the new one is not NULL allowing to
> + * override a subset of phases.
> + */
> +void resettable_class_set_parent_phases(ResettableClass *rc,
> +                                        ResettableEnterPhase enter,
> +                                        ResettableHoldPhase hold,
> +                                        ResettableExitPhase exit,
> +                                        ResettablePhases *parent_phases);
> +
> +#endif
> diff --git a/hw/core/resettable.c b/hw/core/resettable.c
> new file mode 100644
> index 0000000000..9133208487
> --- /dev/null
> +++ b/hw/core/resettable.c
> @@ -0,0 +1,238 @@
> +/*
> + * Resettable interface.
> + *
> + * Copyright (c) 2019 GreenSocs SAS
> + *
> + * Authors:
> + *   Damien Hedde
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qemu/module.h"
> +#include "hw/resettable.h"
> +#include "trace.h"
> +
> +/**
> + * resettable_phase_enter/hold/exit:
> + * Function executing a phase recursively in a resettable object and its
> + * children.
> + */
> +static void resettable_phase_enter(Object *obj, void *opaque, ResetType type);
> +static void resettable_phase_hold(Object *obj, void *opaque, ResetType type);
> +static void resettable_phase_exit(Object *obj, void *opaque, ResetType type);
> +
> +/**
> + * enter_phase_in_progress:
> + * True if we are currently in reset enter phase.
> + *
> + * Note: This flag is only used to guarantee (using asserts) that the reset
> + * API is used correctly. We can use a global variable because we rely on the
> + * iothread mutex to ensure only one reset operation is in a progress at a
> + * given time.
> + */
> +static bool enter_phase_in_progress;
> +
> +void resettable_reset(Object *obj, ResetType type)
> +{
> +    trace_resettable_reset(obj, type);
> +    resettable_assert_reset(obj, type);
> +    resettable_release_reset(obj, type);
> +}
> +
> +void resettable_assert_reset(Object *obj, ResetType type)
> +{
> +    /* TODO: change this assert when adding support for other reset types */
> +    assert(type == RESET_TYPE_COLD);
> +    trace_resettable_reset_assert_begin(obj, type);
> +    assert(!enter_phase_in_progress);
> +
> +    enter_phase_in_progress = true;
> +    resettable_phase_enter(obj, NULL, type);
> +    enter_phase_in_progress = false;
> +
> +    resettable_phase_hold(obj, NULL, type);
> +
> +    trace_resettable_reset_assert_end(obj);
> +}
> +
> +void resettable_release_reset(Object *obj, ResetType type)
> +{
> +    /* TODO: change this assert when adding support for other reset types */
> +    assert(type == RESET_TYPE_COLD);
> +    trace_resettable_reset_release_begin(obj, type);
> +    assert(!enter_phase_in_progress);
> +
> +    resettable_phase_exit(obj, NULL, type);
> +
> +    trace_resettable_reset_release_end(obj);
> +}
> +
> +bool resettable_is_in_reset(Object *obj)
> +{
> +    ResettableClass *rc = RESETTABLE_GET_CLASS(obj);
> +    ResettableState *s = rc->get_state(obj);
> +
> +    return s->count > 0;
> +}
> +
> +/**
> + * resettable_child_foreach:
> + * helper to avoid checking the existence of the method.
> + */
> +static void resettable_child_foreach(ResettableClass *rc, Object *obj,
> +                                     ResettableChildCallback cb,
> +                                     void *opaque, ResetType type)
> +{
> +    if (rc->child_foreach) {
> +        rc->child_foreach(obj, cb, opaque, type);
> +    }
> +}
> +
> +/**
> + * resettable_get_tr_func:
> + * helper to fetch transitional reset callback if any.
> + */
> +static ResettableTrFunction resettable_get_tr_func(ResettableClass *rc,
> +                                                   Object *obj)
> +{
> +    ResettableTrFunction tr_func = NULL;
> +    if (rc->get_transitional_function) {
> +        tr_func = rc->get_transitional_function(obj);
> +    }
> +    return tr_func;
> +}
> +
> +static void resettable_phase_enter(Object *obj, void *opaque, ResetType type)
> +{
> +    ResettableClass *rc = RESETTABLE_GET_CLASS(obj);
> +    ResettableState *s = rc->get_state(obj);
> +    const char *obj_typename = object_get_typename(obj);
> +    bool action_needed = false;
> +
> +    /* exit phase has to finish properly before entering back in reset */
> +    assert(!s->exit_phase_in_progress);
> +
> +    trace_resettable_phase_enter_begin(obj, obj_typename, s->count, type);
> +
> +    /* Only take action if we really enter reset for the 1st time. */
> +    /*
> +     * TODO: if adding more ResetType support, some additional checks
> +     * are probably needed here.
> +     */
> +    if (s->count++ == 0) {
> +        action_needed = true;
> +    }
> +    /*
> +     * We limit the count to an arbitrary "big" value. The value is big
> +     * enough not to be triggered normally.
> +     * The assert will stop an infinite loop if there is a cycle in the
> +     * reset tree. The loop goes through resettable_foreach_child below
> +     * which at some point will call us again.
> +     */
> +    assert(s->count <= 50);
> +
> +    /*
> +     * handle the children even if action_needed is at false so that
> +     * child counts are incremented too
> +     */
> +    resettable_child_foreach(rc, obj, resettable_phase_enter, NULL, type);
> +
> +    /* execute enter phase for the object if needed */
> +    if (action_needed) {
> +        trace_resettable_phase_enter_exec(obj, obj_typename, type,
> +                                          !!rc->phases.enter);
> +        if (rc->phases.enter && !resettable_get_tr_func(rc, obj)) {
> +            rc->phases.enter(obj, type);
> +        }
> +        s->hold_phase_pending = true;
> +    }
> +    trace_resettable_phase_enter_end(obj, obj_typename, s->count);
> +}
> +
> +static void resettable_phase_hold(Object *obj, void *opaque, ResetType type)
> +{
> +    ResettableClass *rc = RESETTABLE_GET_CLASS(obj);
> +    ResettableState *s = rc->get_state(obj);
> +    const char *obj_typename = object_get_typename(obj);
> +
> +    /* exit phase has to finish properly before entering back in reset */
> +    assert(!s->exit_phase_in_progress);
> +
> +    trace_resettable_phase_hold_begin(obj, obj_typename, s->count, type);
> +
> +    /* handle children first */
> +    resettable_child_foreach(rc, obj, resettable_phase_hold, NULL, type);
> +
> +    /* exec hold phase */
> +    if (s->hold_phase_pending) {
> +        s->hold_phase_pending = false;
> +        ResettableTrFunction tr_func = resettable_get_tr_func(rc, obj);
> +        trace_resettable_phase_hold_exec(obj, obj_typename, !!rc->phases.hold);
> +        if (tr_func) {
> +            trace_resettable_transitional_function(obj, obj_typename);
> +            tr_func(obj);
> +        } else if (rc->phases.hold) {
> +            rc->phases.hold(obj);
> +        }
> +    }
> +    trace_resettable_phase_hold_end(obj, obj_typename, s->count);
> +}
> +
> +static void resettable_phase_exit(Object *obj, void *opaque, ResetType type)
> +{
> +    ResettableClass *rc = RESETTABLE_GET_CLASS(obj);
> +    ResettableState *s = rc->get_state(obj);
> +    const char *obj_typename = object_get_typename(obj);
> +
> +    assert(!s->exit_phase_in_progress);
> +    trace_resettable_phase_exit_begin(obj, obj_typename, s->count, type);
> +
> +    /* exit_phase_in_progress ensures this phase is 'atomic' */
> +    s->exit_phase_in_progress = true;
> +    resettable_child_foreach(rc, obj, resettable_phase_exit, NULL, type);
> +
> +    assert(s->count > 0);
> +    if (s->count == 1) {
> +        trace_resettable_phase_exit_exec(obj, obj_typename, !!rc->phases.exit);
> +        if (rc->phases.exit && !resettable_get_tr_func(rc, obj)) {
> +            rc->phases.exit(obj);
> +        }
> +        s->count = 0;
> +    }
> +    s->exit_phase_in_progress = false;
> +    trace_resettable_phase_exit_end(obj, obj_typename, s->count);
> +}
> +
> +void resettable_class_set_parent_phases(ResettableClass *rc,
> +                                        ResettableEnterPhase enter,
> +                                        ResettableHoldPhase hold,
> +                                        ResettableExitPhase exit,
> +                                        ResettablePhases *parent_phases)
> +{
> +    *parent_phases = rc->phases;
> +    if (enter) {
> +        rc->phases.enter = enter;
> +    }
> +    if (hold) {
> +        rc->phases.hold = hold;
> +    }
> +    if (exit) {
> +        rc->phases.exit = exit;
> +    }
> +}
> +
> +static const TypeInfo resettable_interface_info = {
> +    .name       = TYPE_RESETTABLE_INTERFACE,
> +    .parent     = TYPE_INTERFACE,
> +    .class_size = sizeof(ResettableClass),
> +};
> +
> +static void reset_register_types(void)
> +{
> +    type_register_static(&resettable_interface_info);
> +}
> +
> +type_init(reset_register_types)
> diff --git a/hw/core/Makefile.objs b/hw/core/Makefile.objs
> index 0edd9e635d..1709a122d4 100644
> --- a/hw/core/Makefile.objs
> +++ b/hw/core/Makefile.objs
> @@ -1,6 +1,7 @@
>   # core qdev-related obj files, also used by *-user:
>   common-obj-y += qdev.o qdev-properties.o
>   common-obj-y += bus.o reset.o
> +common-obj-y += resettable.o
>   common-obj-$(CONFIG_SOFTMMU) += qdev-fw.o
>   common-obj-$(CONFIG_SOFTMMU) += fw-path-provider.o
>   # irq.o needed for qdev GPIO handling:
> diff --git a/hw/core/trace-events b/hw/core/trace-events
> index a375aa88a4..a2e43f1120 100644
> --- a/hw/core/trace-events
> +++ b/hw/core/trace-events
> @@ -9,3 +9,20 @@ qbus_reset(void *obj, const char *objtype) "obj=%p(%s)"
>   qbus_reset_all(void *obj, const char *objtype) "obj=%p(%s)"
>   qbus_reset_tree(void *obj, const char *objtype) "obj=%p(%s)"
>   qdev_update_parent_bus(void *obj, const char *objtype, void *oldp, const char *oldptype, void *newp, const char *newptype) "obj=%p(%s) old_parent=%p(%s) new_parent=%p(%s)"
> +
> +# resettable.c
> +resettable_reset(void *obj, int cold) "obj=%p cold=%d"
> +resettable_reset_assert_begin(void *obj, int cold) "obj=%p cold=%d"
> +resettable_reset_assert_end(void *obj) "obj=%p"
> +resettable_reset_release_begin(void *obj, int cold) "obj=%p cold=%d"
> +resettable_reset_release_end(void *obj) "obj=%p"
> +resettable_phase_enter_begin(void *obj, const char *objtype, uint32_t count, int type) "obj=%p(%s) count=%" PRIu32 " type=%d"
> +resettable_phase_enter_exec(void *obj, const char *objtype, int type, int has_method) "obj=%p(%s) type=%d method=%d"
> +resettable_phase_enter_end(void *obj, const char *objtype, uint32_t count) "obj=%p(%s) count=%" PRIu32
> +resettable_phase_hold_begin(void *obj, const char *objtype, uint32_t count, int type) "obj=%p(%s) count=%" PRIu32 " type=%d"
> +resettable_phase_hold_exec(void *obj, const char *objtype, int has_method) "obj=%p(%s) method=%d"
> +resettable_phase_hold_end(void *obj, const char *objtype, uint32_t count) "obj=%p(%s) count=%" PRIu32
> +resettable_phase_exit_begin(void *obj, const char *objtype, uint32_t count, int type) "obj=%p(%s) count=%" PRIu32 " type=%d"
> +resettable_phase_exit_exec(void *obj, const char *objtype, int has_method) "obj=%p(%s) method=%d"
> +resettable_phase_exit_end(void *obj, const char *objtype, uint32_t count) "obj=%p(%s) count=%" PRIu32
> +resettable_transitional_function(void *obj, const char *objtype) "obj=%p(%s)"
> 

Re: [PATCH v7 05/11] hw/core/resettable: add support for changing parent

[Philippe Mathieu-Daudé]

On 1/15/20 1:36 PM, Damien Hedde wrote:
> Add a function resettable_change_parent() to do the required
> plumbing when changing the parent a of Resettable object.
> 
> We need to make sure that the reset state of the object remains
> coherent with the reset state of the new parent.
> 
> We make the 2 following hypothesis:
> + when an object is put in a parent under reset, the object goes in
> reset.
> + when an object is removed from a parent under reset, the object
> leaves reset.
> 
> The added function avoids any glitch if both old and new parent are
> already in reset.
> 
> Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>   include/hw/resettable.h | 16 +++++++++++
>   hw/core/resettable.c    | 62 +++++++++++++++++++++++++++++++++++++++--
>   hw/core/trace-events    |  1 +
>   3 files changed, 77 insertions(+), 2 deletions(-)
> 
> diff --git a/include/hw/resettable.h b/include/hw/resettable.h
> index 58b3df4c22..3c87ab86c7 100644
> --- a/include/hw/resettable.h
> +++ b/include/hw/resettable.h
> @@ -194,6 +194,22 @@ void resettable_release_reset(Object *obj, ResetType type);
>    */
>   bool resettable_is_in_reset(Object *obj);
>   
> +/**
> + * resettable_change_parent:
> + * Indicate that the parent of Ressettable @obj is changing from @oldp to @newp.
> + * All 3 objects must implement resettable interface. @oldp or @newp may be
> + * NULL.
> + *
> + * This function will adapt the reset state of @obj so that it is coherent
> + * with the reset state of @newp. It may trigger @resettable_assert_reset()
> + * or @resettable_release_reset(). It will do such things only if the reset
> + * state of @newp and @oldp are different.
> + *
> + * When using this function during reset, it must only be called during
> + * a hold phase method. Calling this during enter or exit phase is an error.
> + */
> +void resettable_change_parent(Object *obj, Object *newp, Object *oldp);
> +
>   /**
>    * resettable_class_set_parent_phases:
>    *
> diff --git a/hw/core/resettable.c b/hw/core/resettable.c
> index 9133208487..e99bb30058 100644
> --- a/hw/core/resettable.c
> +++ b/hw/core/resettable.c
> @@ -28,12 +28,16 @@ static void resettable_phase_exit(Object *obj, void *opaque, ResetType type);
>    * enter_phase_in_progress:
>    * True if we are currently in reset enter phase.
>    *
> - * Note: This flag is only used to guarantee (using asserts) that the reset
> - * API is used correctly. We can use a global variable because we rely on the
> + * exit_phase_in_progress:
> + * count the number of exit phase we are in.
> + *
> + * Note: These flags are only used to guarantee (using asserts) that the reset
> + * API is used correctly. We can use global variables because we rely on the
>    * iothread mutex to ensure only one reset operation is in a progress at a
>    * given time.
>    */
>   static bool enter_phase_in_progress;
> +static unsigned exit_phase_in_progress;
>   
>   void resettable_reset(Object *obj, ResetType type)
>   {
> @@ -65,7 +69,9 @@ void resettable_release_reset(Object *obj, ResetType type)
>       trace_resettable_reset_release_begin(obj, type);
>       assert(!enter_phase_in_progress);
>   
> +    exit_phase_in_progress += 1;
>       resettable_phase_exit(obj, NULL, type);
> +    exit_phase_in_progress -= 1;
>   
>       trace_resettable_reset_release_end(obj);
>   }
> @@ -206,6 +212,58 @@ static void resettable_phase_exit(Object *obj, void *opaque, ResetType type)
>       trace_resettable_phase_exit_end(obj, obj_typename, s->count);
>   }
>   
> +/*
> + * resettable_get_count:
> + * Get the count of the Resettable object @obj. Return 0 if @obj is NULL.
> + */
> +static uint32_t resettable_get_count(Object *obj)

In patch #3 I suggested to use 'unsigned' instead (and add the new 
ResettableState::count field here with the rest of this current patch).

Using 'unsigned' imply trivial format string update in trace events, so 
regardless:

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>

> +{
> +    if (obj) {
> +        ResettableClass *rc = RESETTABLE_GET_CLASS(obj);
> +        return rc->get_state(obj)->count;
> +    }
> +    return 0;
> +}
> +
> +void resettable_change_parent(Object *obj, Object *newp, Object *oldp)
> +{
> +    ResettableClass *rc = RESETTABLE_GET_CLASS(obj);
> +    ResettableState *s = rc->get_state(obj);
> +    uint32_t newp_count = resettable_get_count(newp);
> +    uint32_t oldp_count = resettable_get_count(oldp);
> +
> +    /*
> +     * Ensure we do not change parent when in enter or exit phase.
> +     * During these phases, the reset subtree being updated is partly in reset
> +     * and partly not in reset (it depends on the actual position in
> +     * resettable_child_foreach()s). We are not able to tell in which part is a
> +     * leaving or arriving device. Thus we cannot set the reset count of the
> +     * moving device to the proper value.
> +     */
> +    assert(!enter_phase_in_progress && !exit_phase_in_progress);
> +    trace_resettable_change_parent(obj, oldp, oldp_count, newp, newp_count);
> +
> +    /*
> +     * At most one of the two 'for' loops will be executed below
> +     * in order to cope with the difference between the two counts.
> +     */
> +    /* if newp is more reset than oldp */
> +    for (uint32_t i = oldp_count; i < newp_count; i++) {
> +        resettable_assert_reset(obj, RESET_TYPE_COLD);
> +    }
> +    /*
> +     * if obj is leaving a bus under reset, we need to ensure
> +     * hold phase is not pending.
> +     */
> +    if (oldp_count && s->hold_phase_pending) {
> +        resettable_phase_hold(obj, NULL, RESET_TYPE_COLD);
> +    }
> +    /* if oldp is more reset than newp */
> +    for (uint32_t i = newp_count; i < oldp_count; i++) {
> +        resettable_release_reset(obj, RESET_TYPE_COLD);
> +    }
> +}
> +
>   void resettable_class_set_parent_phases(ResettableClass *rc,
>                                           ResettableEnterPhase enter,
>                                           ResettableHoldPhase hold,
> diff --git a/hw/core/trace-events b/hw/core/trace-events
> index a2e43f1120..80e6325ab0 100644
> --- a/hw/core/trace-events
> +++ b/hw/core/trace-events
> @@ -16,6 +16,7 @@ resettable_reset_assert_begin(void *obj, int cold) "obj=%p cold=%d"
>   resettable_reset_assert_end(void *obj) "obj=%p"
>   resettable_reset_release_begin(void *obj, int cold) "obj=%p cold=%d"
>   resettable_reset_release_end(void *obj) "obj=%p"
> +resettable_change_parent(void *obj, void *o, uint32_t oc, void *n, uint32_t nc) "obj=%p from=%p(%" PRIu32 ") to=%p(%" PRIu32 ")"
>   resettable_phase_enter_begin(void *obj, const char *objtype, uint32_t count, int type) "obj=%p(%s) count=%" PRIu32 " type=%d"
>   resettable_phase_enter_exec(void *obj, const char *objtype, int type, int has_method) "obj=%p(%s) type=%d method=%d"
>   resettable_phase_enter_end(void *obj, const char *objtype, uint32_t count) "obj=%p(%s) count=%" PRIu32
> 

Re: [PATCH v7 07/11] hw/core/qdev: update hotplug reset regarding resettable

[Philippe Mathieu-Daudé]

On 1/15/20 1:36 PM, Damien Hedde wrote:
> This commit make use of the resettable API to reset the device being
> hotplugged when it is realized. Also it ensures it is put in a reset
> state coherent with the parent it is plugged into.
> 
> Note that there is a difference in the reset. Instead of resetting
> only the hotplugged device, we reset also its subtree (switch to
> resettable API). This is not expected to be a problem because
> sub-buses are just realized too. If a hotplugged device has any
> sub-buses it is logical to reset them too at this point.
> 
> The recently added should_be_hidden and PCI's partially_hotplugged
> mechanisms do not interfere with realize operation:
> + In the should_be_hidden use case, device creation is
> delayed.
> + The partially_hotplugged mechanism prevents a device to be
> unplugged and unrealized from qdev POV and unrealized.
> 
> Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
> ---
> 
> v7 update: inline resettable_state_clear()
> 
> v6 update: clear the reset state before doing any reset. Although it
> is apparently highly improbable that a device be realized again after
> being unrealized. See here for a discussion about this point and the
> partially_hotplugged/shoud_be_hidden cases.
> https://lists.nongnu.org/archive/html/qemu-devel/2019-11/msg04897.html
> ---
>   include/hw/resettable.h | 11 +++++++++++
>   hw/core/qdev.c          | 15 ++++++++++++++-
>   2 files changed, 25 insertions(+), 1 deletion(-)
> 
> diff --git a/include/hw/resettable.h b/include/hw/resettable.h
> index 3c87ab86c7..3f90da5b5b 100644
> --- a/include/hw/resettable.h
> +++ b/include/hw/resettable.h
> @@ -153,6 +153,17 @@ struct ResettableState {
>       bool exit_phase_in_progress;
>   };
>   
> +/**
> + * resettable_state_clear:
> + * Clear the state. It puts the state to the initial (zeroed) state required
> + * to reuse an object. Typically used in realize step of base classes
> + * implementing the interface.
> + */
> +static inline void resettable_state_clear(ResettableState *state)
> +{
> +    memset(state, 0, sizeof(ResettableState));
> +}
> +
>   /**
>    * resettable_reset:
>    * Trigger a reset on an object @obj of type @type. @obj must implement
> diff --git a/hw/core/qdev.c b/hw/core/qdev.c
> index 310b87e25a..5fac4cd8fc 100644
> --- a/hw/core/qdev.c
> +++ b/hw/core/qdev.c
> @@ -937,6 +937,12 @@ static void device_set_realized(Object *obj, bool value, Error **errp)
>               }
>           }
>   
> +        /*
> +         * Clear the reset state, in case the object was previously unrealized
> +         * with a dirty state.
> +         */
> +        resettable_state_clear(&dev->reset);
> +
>           QLIST_FOREACH(bus, &dev->child_bus, sibling) {
>               object_property_set_bool(OBJECT(bus), true, "realized",
>                                            &local_err);
> @@ -945,7 +951,14 @@ static void device_set_realized(Object *obj, bool value, Error **errp)
>               }
>           }
>           if (dev->hotplugged) {
> -            device_legacy_reset(dev);
> +            /*
> +             * Reset the device, as well as its subtree which, at this point,
> +             * should be realized too.
> +             */
> +            resettable_assert_reset(OBJECT(dev), RESET_TYPE_COLD);
> +            resettable_change_parent(OBJECT(dev), OBJECT(dev->parent_bus),
> +                                     NULL);
> +            resettable_release_reset(OBJECT(dev), RESET_TYPE_COLD);
>           }
>           dev->pending_deleted_event = false;
>   
> 

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>

Re: [PATCH v7 08/11] hw/core: deprecate old reset functions and introduce new ones

[Philippe Mathieu-Daudé]

On 1/15/20 1:36 PM, Damien Hedde wrote:
> Deprecate device_legacy_reset(), qdev_reset_all() and
> qbus_reset_all() to be replaced by new functions
> device_cold_reset() and bus_cold_reset() which uses resettable API.
> 
> Also introduce resettable_cold_reset_fn() which may be used as a
> replacement for qdev_reset_all_fn and qbus_reset_all_fn().
> 
> Following patches will be needed to look at legacy reset call sites
> and switch to resettable api. The legacy functions will be removed
> when unused.
> 
> Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>   include/hw/qdev-core.h  | 27 +++++++++++++++++++++++++++
>   include/hw/resettable.h |  9 +++++++++
>   hw/core/bus.c           |  5 +++++
>   hw/core/qdev.c          |  5 +++++
>   hw/core/resettable.c    |  5 +++++
>   5 files changed, 51 insertions(+)
> 
> diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
> index 1b4b420617..b84fcc32bf 100644
> --- a/include/hw/qdev-core.h
> +++ b/include/hw/qdev-core.h
> @@ -406,6 +406,13 @@ int qdev_walk_children(DeviceState *dev,
>                          qdev_walkerfn *post_devfn, qbus_walkerfn *post_busfn,
>                          void *opaque);
>   
> +/**
> + * @qdev_reset_all:
> + * Reset @dev. See @qbus_reset_all() for more details.
> + *
> + * Note: This function is deprecated and will be removed when it becomes unused.
> + * Please use device_cold_reset() now.
> + */
>   void qdev_reset_all(DeviceState *dev);
>   void qdev_reset_all_fn(void *opaque);
>   
> @@ -418,10 +425,28 @@ void qdev_reset_all_fn(void *opaque);
>    * hard reset means that qbus_reset_all will reset all state of the device.
>    * For PCI devices, for example, this will include the base address registers
>    * or configuration space.
> + *
> + * Note: This function is deprecated and will be removed when it becomes unused.
> + * Please use bus_cold_reset() now.
>    */
>   void qbus_reset_all(BusState *bus);
>   void qbus_reset_all_fn(void *opaque);
>   
> +/**
> + * device_cold_reset:
> + * Reset device @dev and perform a recursive processing using the resettable
> + * interface. It triggers a RESET_TYPE_COLD.
> + */
> +void device_cold_reset(DeviceState *dev);
> +
> +/**
> + * bus_cold_reset:
> + *
> + * Reset bus @bus and perform a recursive processing using the resettable
> + * interface. It triggers a RESET_TYPE_COLD.
> + */
> +void bus_cold_reset(BusState *bus);
> +
>   /**
>    * device_is_in_reset:
>    * Return true if the device @dev is currently being reset.
> @@ -452,6 +477,8 @@ void qdev_machine_init(void);
>    * device_legacy_reset:
>    *
>    * Reset a single device (by calling the reset method).
> + * Note: This function is deprecated and will be removed when it becomes unused.
> + * Please use device_cold_reset() now.
>    */
>   void device_legacy_reset(DeviceState *dev);
>   
> diff --git a/include/hw/resettable.h b/include/hw/resettable.h
> index 3f90da5b5b..0c1adf49ee 100644
> --- a/include/hw/resettable.h
> +++ b/include/hw/resettable.h
> @@ -221,6 +221,15 @@ bool resettable_is_in_reset(Object *obj);
>    */
>   void resettable_change_parent(Object *obj, Object *newp, Object *oldp);
>   
> +/**
> + * resettable_cold_reset_fn:
> + * Helper to call resettable_reset((Object *) opaque, RESET_TYPE_COLD).
> + *
> + * This function is typically useful to register a reset handler with
> + * qemu_register_reset.
> + */
> +void resettable_cold_reset_fn(void *opaque);
> +
>   /**
>    * resettable_class_set_parent_phases:
>    *
> diff --git a/hw/core/bus.c b/hw/core/bus.c
> index 2698f715bd..3dc0a825f0 100644
> --- a/hw/core/bus.c
> +++ b/hw/core/bus.c
> @@ -68,6 +68,11 @@ int qbus_walk_children(BusState *bus,
>       return 0;
>   }
>   
> +void bus_cold_reset(BusState *bus)
> +{
> +    resettable_reset(OBJECT(bus), RESET_TYPE_COLD);
> +}
> +
>   bool bus_is_in_reset(BusState *bus)
>   {
>       return resettable_is_in_reset(OBJECT(bus));
> diff --git a/hw/core/qdev.c b/hw/core/qdev.c
> index 5fac4cd8fc..a7a7abe569 100644
> --- a/hw/core/qdev.c
> +++ b/hw/core/qdev.c
> @@ -361,6 +361,11 @@ void qbus_reset_all_fn(void *opaque)
>       qbus_reset_all(bus);
>   }
>   
> +void device_cold_reset(DeviceState *dev)
> +{
> +    resettable_reset(OBJECT(dev), RESET_TYPE_COLD);
> +}
> +
>   bool device_is_in_reset(DeviceState *dev)
>   {
>       return resettable_is_in_reset(OBJECT(dev));
> diff --git a/hw/core/resettable.c b/hw/core/resettable.c
> index e99bb30058..7647ef6863 100644
> --- a/hw/core/resettable.c
> +++ b/hw/core/resettable.c
> @@ -264,6 +264,11 @@ void resettable_change_parent(Object *obj, Object *newp, Object *oldp)
>       }
>   }
>   
> +void resettable_cold_reset_fn(void *opaque)
> +{
> +    resettable_reset((Object *) opaque, RESET_TYPE_COLD);
> +}
> +
>   void resettable_class_set_parent_phases(ResettableClass *rc,
>                                           ResettableEnterPhase enter,
>                                           ResettableHoldPhase hold,
> 

Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>

Re: [PATCH v7 01/11] add device_legacy_reset function to prepare for reset api change

[Philippe Mathieu-Daudé]

On 1/15/20 1:36 PM, Damien Hedde wrote:
> Provide a temporary device_legacy_reset function doing what
> device_reset does to prepare for the transition with Resettable
> API.
> 
> All occurrence of device_reset in the code tree are also replaced
> by device_legacy_reset.
> 
> The new resettable API has different prototype and semantics
> (resetting child buses as well as the specified device). Subsequent
> commits will make the changeover for each call site individually; once
> that is complete device_legacy_reset() will be removed.
> 
> Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
> Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
> Acked-by: David Gibson <david@gibson.dropbear.id.au>
> Acked-by: Cornelia Huck <cohuck@redhat.com>
> ---
> v7 update: added new occurence due to rebase
> 
> Cc: Gerd Hoffmann <kraxel@redhat.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: "Daniel P. Berrangé" <berrange@redhat.com>
> Cc: Eduardo Habkost <ehabkost@redhat.com>
> Cc: Richard Henderson <rth@twiddle.net>
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Cc: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
> Cc: John Snow <jsnow@redhat.com>
> Cc: "Cédric Le Goater" <clg@kaod.org>
> Cc: Collin Walling <walling@linux.ibm.com>
> Cc: Cornelia Huck <cohuck@redhat.com>
> Cc: David Hildenbrand <david@redhat.com>
> Cc: Halil Pasic <pasic@linux.ibm.com>
> Cc: Christian Borntraeger <borntraeger@de.ibm.com>
> Cc: Dmitry Fleytman <dmitry.fleytman@gmail.com>
> Cc: Fam Zheng <fam@euphon.net>
> ---
>   include/hw/qdev-core.h   | 4 ++--
>   hw/audio/intel-hda.c     | 2 +-
>   hw/core/qdev.c           | 6 +++---
>   hw/hyperv/hyperv.c       | 2 +-
>   hw/i386/microvm.c        | 2 +-
>   hw/i386/pc.c             | 2 +-
>   hw/ide/microdrive.c      | 8 ++++----
>   hw/intc/spapr_xive.c     | 2 +-
>   hw/ppc/pnv_psi.c         | 4 ++--
>   hw/ppc/spapr_pci.c       | 2 +-
>   hw/ppc/spapr_vio.c       | 2 +-
>   hw/s390x/s390-pci-inst.c | 2 +-
>   hw/scsi/vmw_pvscsi.c     | 2 +-
>   hw/sd/omap_mmc.c         | 2 +-
>   hw/sd/pl181.c            | 2 +-
>   15 files changed, 22 insertions(+), 22 deletions(-)
> 
> diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
> index 1518495b1e..b8341b0fb0 100644
> --- a/include/hw/qdev-core.h
> +++ b/include/hw/qdev-core.h
> @@ -427,11 +427,11 @@ char *qdev_get_own_fw_dev_path_from_handler(BusState *bus, DeviceState *dev);
>   void qdev_machine_init(void);
>   
>   /**
> - * @device_reset
> + * device_legacy_reset:
>    *
>    * Reset a single device (by calling the reset method).
>    */
> -void device_reset(DeviceState *dev);
> +void device_legacy_reset(DeviceState *dev);
>   
>   void device_class_set_parent_reset(DeviceClass *dc,
>                                      DeviceReset dev_reset,
> diff --git a/hw/audio/intel-hda.c b/hw/audio/intel-hda.c
> index 6ecd383540..27b71c57cf 100644
> --- a/hw/audio/intel-hda.c
> +++ b/hw/audio/intel-hda.c
> @@ -1087,7 +1087,7 @@ static void intel_hda_reset(DeviceState *dev)
>       QTAILQ_FOREACH(kid, &d->codecs.qbus.children, sibling) {
>           DeviceState *qdev = kid->child;
>           cdev = HDA_CODEC_DEVICE(qdev);
> -        device_reset(DEVICE(cdev));
> +        device_legacy_reset(DEVICE(cdev));
>           d->state_sts |= (1 << cdev->cad);
>       }
>       intel_hda_update_irq(d);
> diff --git a/hw/core/qdev.c b/hw/core/qdev.c
> index 9f1753f5cf..8c0c8284c8 100644
> --- a/hw/core/qdev.c
> +++ b/hw/core/qdev.c
> @@ -298,7 +298,7 @@ HotplugHandler *qdev_get_hotplug_handler(DeviceState *dev)
>   
>   static int qdev_reset_one(DeviceState *dev, void *opaque)
>   {
> -    device_reset(dev);
> +    device_legacy_reset(dev);
>   
>       return 0;
>   }
> @@ -895,7 +895,7 @@ static void device_set_realized(Object *obj, bool value, Error **errp)
>               }
>           }
>           if (dev->hotplugged) {
> -            device_reset(dev);
> +            device_legacy_reset(dev);
>           }
>           dev->pending_deleted_event = false;
>   
> @@ -1127,7 +1127,7 @@ void device_class_set_parent_unrealize(DeviceClass *dc,
>       dc->unrealize = dev_unrealize;
>   }
>   
> -void device_reset(DeviceState *dev)
> +void device_legacy_reset(DeviceState *dev)
>   {
>       DeviceClass *klass = DEVICE_GET_CLASS(dev);
>   
> diff --git a/hw/hyperv/hyperv.c b/hw/hyperv/hyperv.c
> index da8ce82725..8ca3706f5b 100644
> --- a/hw/hyperv/hyperv.c
> +++ b/hw/hyperv/hyperv.c
> @@ -140,7 +140,7 @@ void hyperv_synic_reset(CPUState *cs)
>       SynICState *synic = get_synic(cs);
>   
>       if (synic) {
> -        device_reset(DEVICE(synic));
> +        device_legacy_reset(DEVICE(synic));
>       }
>   }
>   
> diff --git a/hw/i386/microvm.c b/hw/i386/microvm.c
> index 827ce29e58..d23485108d 100644
> --- a/hw/i386/microvm.c
> +++ b/hw/i386/microvm.c
> @@ -370,7 +370,7 @@ static void microvm_machine_reset(MachineState *machine)
>           cpu = X86_CPU(cs);
>   
>           if (cpu->apic_state) {
> -            device_reset(cpu->apic_state);
> +            device_legacy_reset(cpu->apic_state);
>           }
>       }
>   }
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index 8054bc4147..91c7fdaab1 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -1877,7 +1877,7 @@ static void pc_machine_reset(MachineState *machine)
>           cpu = X86_CPU(cs);
>   
>           if (cpu->apic_state) {
> -            device_reset(cpu->apic_state);
> +            device_legacy_reset(cpu->apic_state);
>           }
>       }
>   }
> diff --git a/hw/ide/microdrive.c b/hw/ide/microdrive.c
> index b0272ea14b..6b30e36ed8 100644
> --- a/hw/ide/microdrive.c
> +++ b/hw/ide/microdrive.c
> @@ -173,7 +173,7 @@ static void md_attr_write(PCMCIACardState *card, uint32_t at, uint8_t value)
>       case 0x00:	/* Configuration Option Register */
>           s->opt = value & 0xcf;
>           if (value & OPT_SRESET) {
> -            device_reset(DEVICE(s));
> +            device_legacy_reset(DEVICE(s));
>           }
>           md_interrupt_update(s);
>           break;
> @@ -316,7 +316,7 @@ static void md_common_write(PCMCIACardState *card, uint32_t at, uint16_t value)
>       case 0xe:	/* Device Control */
>           s->ctrl = value;
>           if (value & CTRL_SRST) {
> -            device_reset(DEVICE(s));
> +            device_legacy_reset(DEVICE(s));
>           }
>           md_interrupt_update(s);
>           break;
> @@ -541,7 +541,7 @@ static int dscm1xxxx_attach(PCMCIACardState *card)
>       md->attr_base = pcc->cis[0x74] | (pcc->cis[0x76] << 8);
>       md->io_base = 0x0;
>   
> -    device_reset(DEVICE(md));
> +    device_legacy_reset(DEVICE(md));
>       md_interrupt_update(md);
>   
>       return 0;
> @@ -551,7 +551,7 @@ static int dscm1xxxx_detach(PCMCIACardState *card)
>   {
>       MicroDriveState *md = MICRODRIVE(card);
>   
> -    device_reset(DEVICE(md));
> +    device_legacy_reset(DEVICE(md));
>       return 0;
>   }
>   
> diff --git a/hw/intc/spapr_xive.c b/hw/intc/spapr_xive.c
> index 7663123878..52bab29784 100644
> --- a/hw/intc/spapr_xive.c
> +++ b/hw/intc/spapr_xive.c
> @@ -1766,7 +1766,7 @@ static target_ulong h_int_reset(PowerPCCPU *cpu,
>           return H_PARAMETER;
>       }
>   
> -    device_reset(DEVICE(xive));
> +    device_legacy_reset(DEVICE(xive));
>   
>       if (kvm_irqchip_in_kernel()) {
>           Error *local_err = NULL;
> diff --git a/hw/ppc/pnv_psi.c b/hw/ppc/pnv_psi.c
> index 1d8da31738..916e2a9ba7 100644
> --- a/hw/ppc/pnv_psi.c
> +++ b/hw/ppc/pnv_psi.c
> @@ -466,7 +466,7 @@ static void pnv_psi_reset(DeviceState *dev)
>   
>   static void pnv_psi_reset_handler(void *dev)
>   {
> -    device_reset(DEVICE(dev));
> +    device_legacy_reset(DEVICE(dev));
>   }
>   
>   static void pnv_psi_realize(DeviceState *dev, Error **errp)
> @@ -715,7 +715,7 @@ static void pnv_psi_p9_mmio_write(void *opaque, hwaddr addr,
>           break;
>       case PSIHB9_INTERRUPT_CONTROL:
>           if (val & PSIHB9_IRQ_RESET) {
> -            device_reset(DEVICE(&psi9->source));
> +            device_legacy_reset(DEVICE(&psi9->source));
>           }
>           psi->regs[reg] = val;
>           break;
> diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
> index 723373de73..81b5d1b6f2 100644
> --- a/hw/ppc/spapr_pci.c
> +++ b/hw/ppc/spapr_pci.c
> @@ -2014,7 +2014,7 @@ static int spapr_phb_children_reset(Object *child, void *opaque)
>       DeviceState *dev = (DeviceState *) object_dynamic_cast(child, TYPE_DEVICE);
>   
>       if (dev) {
> -        device_reset(dev);
> +        device_legacy_reset(dev);
>       }
>   
>       return 0;
> diff --git a/hw/ppc/spapr_vio.c b/hw/ppc/spapr_vio.c
> index 554de9930d..f14944e900 100644
> --- a/hw/ppc/spapr_vio.c
> +++ b/hw/ppc/spapr_vio.c
> @@ -304,7 +304,7 @@ int spapr_vio_send_crq(SpaprVioDevice *dev, uint8_t *crq)
>   static void spapr_vio_quiesce_one(SpaprVioDevice *dev)
>   {
>       if (dev->tcet) {
> -        device_reset(DEVICE(dev->tcet));
> +        device_legacy_reset(DEVICE(dev->tcet));
>       }
>       free_crq(dev);
>   }
> diff --git a/hw/s390x/s390-pci-inst.c b/hw/s390x/s390-pci-inst.c
> index 92c7e45df5..2f7a7d7bd1 100644
> --- a/hw/s390x/s390-pci-inst.c
> +++ b/hw/s390x/s390-pci-inst.c
> @@ -243,7 +243,7 @@ int clp_service_call(S390CPU *cpu, uint8_t r2, uintptr_t ra)
>                   stw_p(&ressetpci->hdr.rsp, CLP_RC_SETPCIFN_FHOP);
>                   goto out;
>               }
> -            device_reset(DEVICE(pbdev));
> +            device_legacy_reset(DEVICE(pbdev));
>               pbdev->fh &= ~FH_MASK_ENABLE;
>               pbdev->state = ZPCI_FS_DISABLED;
>               stl_p(&ressetpci->fh, pbdev->fh);
> diff --git a/hw/scsi/vmw_pvscsi.c b/hw/scsi/vmw_pvscsi.c
> index 452a3b63b2..7baab1532f 100644
> --- a/hw/scsi/vmw_pvscsi.c
> +++ b/hw/scsi/vmw_pvscsi.c
> @@ -838,7 +838,7 @@ pvscsi_on_cmd_reset_device(PVSCSIState *s)
>   
>       if (sdev != NULL) {
>           s->resetting++;
> -        device_reset(&sdev->qdev);
> +        device_legacy_reset(&sdev->qdev);
>           s->resetting--;
>           return PVSCSI_COMMAND_PROCESSING_SUCCEEDED;
>       }
> diff --git a/hw/sd/omap_mmc.c b/hw/sd/omap_mmc.c
> index c6e516b611..4088a8a80b 100644
> --- a/hw/sd/omap_mmc.c
> +++ b/hw/sd/omap_mmc.c
> @@ -318,7 +318,7 @@ void omap_mmc_reset(struct omap_mmc_s *host)
>        * into any bus, and we must reset it manually. When omap_mmc is
>        * QOMified this must move into the QOM reset function.
>        */
> -    device_reset(DEVICE(host->card));
> +    device_legacy_reset(DEVICE(host->card));
>   }
>   
>   static uint64_t omap_mmc_read(void *opaque, hwaddr offset,
> diff --git a/hw/sd/pl181.c b/hw/sd/pl181.c
> index 8033fe455d..2b3776a6a0 100644
> --- a/hw/sd/pl181.c
> +++ b/hw/sd/pl181.c
> @@ -482,7 +482,7 @@ static void pl181_reset(DeviceState *d)
>       /* Since we're still using the legacy SD API the card is not plugged
>        * into any bus, and we must reset it manually.
>        */
> -    device_reset(DEVICE(s->card));
> +    device_legacy_reset(DEVICE(s->card));
>   }
>   
>   static void pl181_init(Object *obj)
> 

Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>

Re: [PATCH v7 03/11] hw/core: create Resettable QOM interface

[Damien Hedde]

On 1/18/20 7:35 AM, Philippe Mathieu-Daudé wrote:
> On 1/15/20 1:36 PM, Damien Hedde wrote:
>> This commit defines an interface allowing multi-phase reset. This aims
>> to solve a problem of the actual single-phase reset (built in
>> DeviceClass and BusClass): reset behavior is dependent on the order
>> in which reset handlers are called. In particular doing external
>> side-effect (like setting an qemu_irq) is problematic because receiving
>> object may not be reset yet.
>>
>> The Resettable interface divides the reset in 3 well defined phases.
>> To reset an object tree, all 1st phases are executed then all 2nd then
>> all 3rd. See the comments in include/hw/resettable.h for a more complete
>> description. The interface defines 3 phases to let the future
>> possibility of holding an object into reset for some time.
>>
>> The qdev/qbus reset in DeviceClass and BusClass will be modified in
>> following commits to use this interface. A mechanism is provided
>> to allow executing a transitional reset handler in place of the 2nd
>> phase which is executed in children-then-parent order inside a tree.
>> This will allow to transition devices and buses smoothly while
>> keeping the exact current qdev/qbus reset behavior for now.
>>
>> Documentation will be added in a following commit.
>>
>> Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
>> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
>> ---
>>
>> v7 update: un-nest struct ResettablePhases
>> ---
>>   Makefile.objs           |   1 +
>>   include/hw/resettable.h | 211 +++++++++++++++++++++++++++++++++++
>>   hw/core/resettable.c    | 238 ++++++++++++++++++++++++++++++++++++++++
>>   hw/core/Makefile.objs   |   1 +
>>   hw/core/trace-events    |  17 +++
>>   5 files changed, 468 insertions(+)
>>   create mode 100644 include/hw/resettable.h
>>   create mode 100644 hw/core/resettable.c
>>
>> diff --git a/Makefile.objs b/Makefile.objs
>> index 7c1e50f9d6..9752d549b4 100644
>> --- a/Makefile.objs
>> +++ b/Makefile.objs
>> @@ -191,6 +191,7 @@ trace-events-subdirs += migration
>>   trace-events-subdirs += net
>>   trace-events-subdirs += ui
>>   endif
>> +trace-events-subdirs += hw/core
>>   trace-events-subdirs += hw/display
>>   trace-events-subdirs += qapi
>>   trace-events-subdirs += qom
>> diff --git a/include/hw/resettable.h b/include/hw/resettable.h
>> new file mode 100644
>> index 0000000000..58b3df4c22
>> --- /dev/null
>> +++ b/include/hw/resettable.h
>> @@ -0,0 +1,211 @@
>> +/*
>> + * Resettable interface header.
>> + *
>> + * Copyright (c) 2019 GreenSocs SAS
>> + *
>> + * Authors:
>> + *   Damien Hedde
>> + *
>> + * This work is licensed under the terms of the GNU GPL, version 2 or
>> later.
>> + * See the COPYING file in the top-level directory.
>> + */
>> +
>> +#ifndef HW_RESETTABLE_H
>> +#define HW_RESETTABLE_H
>> +
>> +#include "qom/object.h"
>> +
>> +#define TYPE_RESETTABLE_INTERFACE "resettable"
>> +
>> +#define RESETTABLE_CLASS(class) \
>> +    OBJECT_CLASS_CHECK(ResettableClass, (class),
>> TYPE_RESETTABLE_INTERFACE)
>> +
>> +#define RESETTABLE_GET_CLASS(obj) \
>> +    OBJECT_GET_CLASS(ResettableClass, (obj), TYPE_RESETTABLE_INTERFACE)
>> +
>> +typedef struct ResettableState ResettableState;
>> +
>> +/**
>> + * ResetType:
>> + * Types of reset.
>> + *
>> + * + Cold: reset resulting from a power cycle of the object.
>> + *
>> + * TODO: Support has to be added to handle more types. In particular,
>> + * ResettableState structure needs to be expanded.
>> + */
>> +typedef enum ResetType {
>> +    RESET_TYPE_COLD,
>> +} ResetType;
>> +
>> +/*
>> + * ResettableClass:
>> + * Interface for resettable objects.
>> + *
>> + * See docs/devel/reset.rst for more detailed information about how
>> QEMU models
>> + * reset. This whole API must only be used when holding the iothread
>> mutex.
>> + *
>> + * All objects which can be reset must implement this interface;
>> + * it is usually provided by a base class such as DeviceClass or
>> BusClass.
>> + * Every Resettable object must maintain some state tracking the
>> + * progress of a reset operation by providing a ResettableState
>> structure.
>> + * The functions defined in this module take care of updating the
>> + * state of the reset.
>> + * The base class implementation of the interface provides this
>> + * state and implements the associated method: get_state.
>> + *
>> + * Concrete object implementations (typically specific devices
>> + * such as a UART model) should provide the functions
>> + * for the phases.enter, phases.hold and phases.exit methods, which
>> + * they can set in their class init function, either directly or
>> + * by calling resettable_class_set_parent_phases().
>> + * The phase methods are guaranteed to only only ever be called once
>> + * for any reset event, in the order 'enter', 'hold', 'exit'.
>> + * An object will always move quickly from 'enter' to 'hold'
>> + * but might remain in 'hold' for an arbitrary period of time
>> + * before eventually reset is deasserted and the 'exit' phase is called.
>> + * Object implementations should be prepared for functions handling
>> + * inbound connections from other devices (such as qemu_irq handler
>> + * functions) to be called at any point during reset after their
>> + * 'enter' method has been called.
>> + *
>> + * Users of a resettable object should not call these methods
>> + * directly, but instead use the function resettable_reset().
>> + *
>> + * @phases.enter: This phase is called when the object enters reset. It
>> + * should reset local state of the object, but it must not do
>> anything that
>> + * has a side-effect on other objects, such as raising or lowering a
>> qemu_irq
>> + * line or reading or writing guest memory. It takes the reset's type as
>> + * argument.
>> + *
>> + * @phases.hold: This phase is called for entry into reset, once
>> every object
>> + * in the system which is being reset has had its @phases.enter
>> method called.
>> + * At this point devices can do actions that affect other objects.
>> + *
>> + * @phases.exit: This phase is called when the object leaves the
>> reset state.
>> + * Actions affecting other objects are permitted.
>> + *
>> + * @get_state: Mandatory method which must return a pointer to a
>> + * ResettableState.
>> + *
>> + * @get_transitional_function: transitional method to handle
>> Resettable objects
>> + * not yet fully moved to this interface. It will be removed as soon
>> as it is
>> + * not needed anymore. This method is optional and may return a
>> pointer to a
>> + * function to be used instead of the phases. If the method exists
>> and returns
>> + * a non-NULL function pointer then that function is executed as a
>> replacement
>> + * of the 'hold' phase method taking the object as argument. The two
>> other phase
>> + * methods are not executed.
>> + *
>> + * @child_foreach: Executes a given callback on every Resettable
>> child. Child
>> + * in this context means a child in the qbus tree, so the children of
>> a qbus
>> + * are the devices on it, and the children of a device are all the
>> buses it
>> + * owns. This is not the same as the QOM object hierarchy. The
>> function takes
>> + * additional opaque and ResetType arguments which must be passed
>> unmodified to
>> + * the callback.
>> + */
>> +typedef void (*ResettableEnterPhase)(Object *obj, ResetType type);
>> +typedef void (*ResettableHoldPhase)(Object *obj);
>> +typedef void (*ResettableExitPhase)(Object *obj);
>> +typedef ResettableState * (*ResettableGetState)(Object *obj);
>> +typedef void (*ResettableTrFunction)(Object *obj);
>> +typedef ResettableTrFunction (*ResettableGetTrFunction)(Object *obj);
>> +typedef void (*ResettableChildCallback)(Object *, void *opaque,
>> +                                        ResetType type);
>> +typedef void (*ResettableChildForeach)(Object *obj,
>> +                                       ResettableChildCallback cb,
>> +                                       void *opaque, ResetType type);
>> +typedef struct ResettablePhases {
>> +    ResettableEnterPhase enter;
>> +    ResettableHoldPhase hold;
>> +    ResettableExitPhase exit;
>> +} ResettablePhases;
>> +typedef struct ResettableClass {
>> +    InterfaceClass parent_class;
>> +
>> +    /* Phase methods */
>> +    ResettablePhases phases;
>> +
>> +    /* State access method */
>> +    ResettableGetState get_state;
>> +
>> +    /* Transitional method for legacy reset compatibility */
>> +    ResettableGetTrFunction get_transitional_function;
>> +
>> +    /* Hierarchy handling method */
>> +    ResettableChildForeach child_foreach;
>> +} ResettableClass;
>> +
>> +/**
>> + * ResettableState:
>> + * Structure holding reset related state. The fields should not be
>> accessed
>> + * directly; the definition is here to allow further inclusion into
>> other
>> + * objects.
>> + *
>> + * @count: Number of reset level the object is into. It is
>> incremented when
>> + * the reset operation starts and decremented when it finishes.
>> + * @hold_phase_pending: flag which indicates that we need to invoke
>> the 'hold'
>> + * phase handler for this object.
>> + * @exit_phase_in_progress: true if we are currently in the exit phase
>> + */
>> +struct ResettableState {
>> +    uint32_t count;
>> +    bool hold_phase_pending;
>> +    bool exit_phase_in_progress;
>> +};
>> +
>> +/**
>> + * resettable_reset:
>> + * Trigger a reset on an object @obj of type @type. @obj must implement
>> + * Resettable interface.
>> + *
>> + * Calling this function is equivalent to calling
>> @resettable_assert_reset()
>> + * then @resettable_release_reset().
>> + */
>> +void resettable_reset(Object *obj, ResetType type);
>> +
>> +/**
>> + * resettable_assert_reset:
>> + * Put an object @obj into reset. @obj must implement Resettable
>> interface.
>> + *
>> + * @resettable_release_reset() must eventually be called after this
>> call.
>> + * There must be one call to @resettable_release_reset() per call of
>> + * @resettable_assert_reset(), with the same type argument.
>> + *
>> + * NOTE: Until support for migration is added, the
>> @resettable_release_reset()
>> + * must not be delayed. It must occur just after
>> @resettable_assert_reset() so
>> + * that migration cannot be triggered in between. Prefer using
>> + * @resettable_reset() for now.
>> + */
>> +void resettable_assert_reset(Object *obj, ResetType type);
>> +
>> +/**
>> + * resettable_release_reset:
>> + * Release the object @obj from reset. @obj must implement Resettable
>> interface.
>> + *
>> + * See @resettable_assert_reset() description for details.
>> + */
>> +void resettable_release_reset(Object *obj, ResetType type);
>> +
>> +/**
>> + * resettable_is_in_reset:
>> + * Return true if @obj is under reset.
>> + *
>> + * @obj must implement Resettable interface.
>> + */
>> +bool resettable_is_in_reset(Object *obj);
>> +
>> +/**
>> + * resettable_class_set_parent_phases:
>> + *
>> + * Save @rc current reset phases into @parent_phases and override @rc
>> phases
>> + * by the given new methods (@enter, @hold and @exit).
>> + * Each phase is overridden only if the new one is not NULL allowing to
>> + * override a subset of phases.
>> + */
>> +void resettable_class_set_parent_phases(ResettableClass *rc,
>> +                                        ResettableEnterPhase enter,
>> +                                        ResettableHoldPhase hold,
>> +                                        ResettableExitPhase exit,
>> +                                        ResettablePhases
>> *parent_phases);
>> +
>> +#endif
>> diff --git a/hw/core/resettable.c b/hw/core/resettable.c
>> new file mode 100644
>> index 0000000000..9133208487
>> --- /dev/null
>> +++ b/hw/core/resettable.c
>> @@ -0,0 +1,238 @@
>> +/*
>> + * Resettable interface.
>> + *
>> + * Copyright (c) 2019 GreenSocs SAS
>> + *
>> + * Authors:
>> + *   Damien Hedde
>> + *
>> + * This work is licensed under the terms of the GNU GPL, version 2 or
>> later.
>> + * See the COPYING file in the top-level directory.
>> + */
>> +
>> +#include "qemu/osdep.h"
>> +#include "qemu/module.h"
>> +#include "hw/resettable.h"
>> +#include "trace.h"
>> +
>> +/**
>> + * resettable_phase_enter/hold/exit:
>> + * Function executing a phase recursively in a resettable object and its
>> + * children.
>> + */
>> +static void resettable_phase_enter(Object *obj, void *opaque,
>> ResetType type);
>> +static void resettable_phase_hold(Object *obj, void *opaque,
>> ResetType type);
>> +static void resettable_phase_exit(Object *obj, void *opaque,
>> ResetType type);
>> +
>> +/**
>> + * enter_phase_in_progress:
>> + * True if we are currently in reset enter phase.
>> + *
>> + * Note: This flag is only used to guarantee (using asserts) that the
>> reset
>> + * API is used correctly. We can use a global variable because we
>> rely on the
>> + * iothread mutex to ensure only one reset operation is in a progress
>> at a
>> + * given time.
>> + */
>> +static bool enter_phase_in_progress;
>> +
>> +void resettable_reset(Object *obj, ResetType type)
>> +{
>> +    trace_resettable_reset(obj, type);
>> +    resettable_assert_reset(obj, type);
>> +    resettable_release_reset(obj, type);
>> +}
>> +
>> +void resettable_assert_reset(Object *obj, ResetType type)
>> +{
>> +    /* TODO: change this assert when adding support for other reset
>> types */
>> +    assert(type == RESET_TYPE_COLD);
>> +    trace_resettable_reset_assert_begin(obj, type);
>> +    assert(!enter_phase_in_progress);
>> +
>> +    enter_phase_in_progress = true;
>> +    resettable_phase_enter(obj, NULL, type);
>> +    enter_phase_in_progress = false;
>> +
>> +    resettable_phase_hold(obj, NULL, type);
>> +
>> +    trace_resettable_reset_assert_end(obj);
>> +}
>> +
>> +void resettable_release_reset(Object *obj, ResetType type)
>> +{
>> +    /* TODO: change this assert when adding support for other reset
>> types */
>> +    assert(type == RESET_TYPE_COLD);
>> +    trace_resettable_reset_release_begin(obj, type);
>> +    assert(!enter_phase_in_progress);
>> +
>> +    resettable_phase_exit(obj, NULL, type);
>> +
>> +    trace_resettable_reset_release_end(obj);
>> +}
>> +
>> +bool resettable_is_in_reset(Object *obj)
>> +{
>> +    ResettableClass *rc = RESETTABLE_GET_CLASS(obj);
>> +    ResettableState *s = rc->get_state(obj);
>> +
>> +    return s->count > 0;
>> +}
>> +
>> +/**
>> + * resettable_child_foreach:
>> + * helper to avoid checking the existence of the method.
>> + */
>> +static void resettable_child_foreach(ResettableClass *rc, Object *obj,
>> +                                     ResettableChildCallback cb,
>> +                                     void *opaque, ResetType type)
>> +{
>> +    if (rc->child_foreach) {
>> +        rc->child_foreach(obj, cb, opaque, type);
>> +    }
>> +}
>> +
>> +/**
>> + * resettable_get_tr_func:
>> + * helper to fetch transitional reset callback if any.
>> + */
>> +static ResettableTrFunction resettable_get_tr_func(ResettableClass *rc,
>> +                                                   Object *obj)
>> +{
>> +    ResettableTrFunction tr_func = NULL;
>> +    if (rc->get_transitional_function) {
>> +        tr_func = rc->get_transitional_function(obj);
>> +    }
>> +    return tr_func;
>> +}
>> +
>> +static void resettable_phase_enter(Object *obj, void *opaque,
>> ResetType type)
>> +{
>> +    ResettableClass *rc = RESETTABLE_GET_CLASS(obj);
>> +    ResettableState *s = rc->get_state(obj);
>> +    const char *obj_typename = object_get_typename(obj);
>> +    bool action_needed = false;
>> +
>> +    /* exit phase has to finish properly before entering back in
>> reset */
>> +    assert(!s->exit_phase_in_progress);
>> +
>> +    trace_resettable_phase_enter_begin(obj, obj_typename, s->count,
>> type);
>> +
>> +    /* Only take action if we really enter reset for the 1st time. */
>> +    /*
>> +     * TODO: if adding more ResetType support, some additional checks
>> +     * are probably needed here.
>> +     */
>> +    if (s->count++ == 0) {
>> +        action_needed = true;
>> +    }
>> +    /*
>> +     * We limit the count to an arbitrary "big" value. The value is big
>> +     * enough not to be triggered normally.
>> +     * The assert will stop an infinite loop if there is a cycle in the
>> +     * reset tree. The loop goes through resettable_foreach_child below
>> +     * which at some point will call us again.
>> +     */
>> +    assert(s->count <= 50);
>> +
>> +    /*
>> +     * handle the children even if action_needed is at false so that
>> +     * child counts are incremented too
>> +     */
>> +    resettable_child_foreach(rc, obj, resettable_phase_enter, NULL,
>> type);
>> +
>> +    /* execute enter phase for the object if needed */
>> +    if (action_needed) {
>> +        trace_resettable_phase_enter_exec(obj, obj_typename, type,
>> +                                          !!rc->phases.enter);
>> +        if (rc->phases.enter && !resettable_get_tr_func(rc, obj)) {
>> +            rc->phases.enter(obj, type);
>> +        }
>> +        s->hold_phase_pending = true;
>> +    }
>> +    trace_resettable_phase_enter_end(obj, obj_typename, s->count);
>> +}
>> +
>> +static void resettable_phase_hold(Object *obj, void *opaque,
>> ResetType type)
>> +{
>> +    ResettableClass *rc = RESETTABLE_GET_CLASS(obj);
>> +    ResettableState *s = rc->get_state(obj);
>> +    const char *obj_typename = object_get_typename(obj);
>> +
>> +    /* exit phase has to finish properly before entering back in
>> reset */
>> +    assert(!s->exit_phase_in_progress);
>> +
>> +    trace_resettable_phase_hold_begin(obj, obj_typename, s->count,
>> type);
>> +
>> +    /* handle children first */
>> +    resettable_child_foreach(rc, obj, resettable_phase_hold, NULL,
>> type);
>> +
>> +    /* exec hold phase */
>> +    if (s->hold_phase_pending) {
>> +        s->hold_phase_pending = false;
>> +        ResettableTrFunction tr_func = resettable_get_tr_func(rc, obj);
>> +        trace_resettable_phase_hold_exec(obj, obj_typename,
>> !!rc->phases.hold);
>> +        if (tr_func) {
>> +            trace_resettable_transitional_function(obj, obj_typename);
>> +            tr_func(obj);
>> +        } else if (rc->phases.hold) {
>> +            rc->phases.hold(obj);
>> +        }
>> +    }
>> +    trace_resettable_phase_hold_end(obj, obj_typename, s->count);
>> +}
>> +
>> +static void resettable_phase_exit(Object *obj, void *opaque,
>> ResetType type)
>> +{
>> +    ResettableClass *rc = RESETTABLE_GET_CLASS(obj);
>> +    ResettableState *s = rc->get_state(obj);
>> +    const char *obj_typename = object_get_typename(obj);
>> +
>> +    assert(!s->exit_phase_in_progress);
>> +    trace_resettable_phase_exit_begin(obj, obj_typename, s->count,
>> type);
>> +
>> +    /* exit_phase_in_progress ensures this phase is 'atomic' */
>> +    s->exit_phase_in_progress = true;
>> +    resettable_child_foreach(rc, obj, resettable_phase_exit, NULL,
>> type);
>> +
>> +    assert(s->count > 0);
>> +    if (s->count == 1) {
>> +        trace_resettable_phase_exit_exec(obj, obj_typename,
>> !!rc->phases.exit);
>> +        if (rc->phases.exit && !resettable_get_tr_func(rc, obj)) {
>> +            rc->phases.exit(obj);
>> +        }
>> +        s->count = 0;
>> +    }
>> +    s->exit_phase_in_progress = false;
>> +    trace_resettable_phase_exit_end(obj, obj_typename, s->count);
>> +}
>> +
>> +void resettable_class_set_parent_phases(ResettableClass *rc,
>> +                                        ResettableEnterPhase enter,
>> +                                        ResettableHoldPhase hold,
>> +                                        ResettableExitPhase exit,
>> +                                        ResettablePhases *parent_phases)
>> +{
>> +    *parent_phases = rc->phases;
>> +    if (enter) {
> 
> Why care about checking if handlers are not NULL? It is not like you are
> overwriting a pointer previously set.

It may be previously set. You may just want to override one of the 3
phases and inherit the 2 others from the parent class version.

> 
> Anyway:
> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> 
>> +        rc->phases.enter = enter;
>> +    }
>> +    if (hold) {
>> +        rc->phases.hold = hold;
>> +    }
>> +    if (exit) {
>> +        rc->phases.exit = exit;
>> +    }
>> +}
>> +
>> +static const TypeInfo resettable_interface_info = {
>> +    .name       = TYPE_RESETTABLE_INTERFACE,
>> +    .parent     = TYPE_INTERFACE,
>> +    .class_size = sizeof(ResettableClass),
>> +};
>> +
>> +static void reset_register_types(void)
>> +{
>> +    type_register_static(&resettable_interface_info);
>> +}
>> +
>> +type_init(reset_register_types)
>> diff --git a/hw/core/Makefile.objs b/hw/core/Makefile.objs
>> index 0edd9e635d..1709a122d4 100644
>> --- a/hw/core/Makefile.objs
>> +++ b/hw/core/Makefile.objs
>> @@ -1,6 +1,7 @@
>>   # core qdev-related obj files, also used by *-user:
>>   common-obj-y += qdev.o qdev-properties.o
>>   common-obj-y += bus.o reset.o
>> +common-obj-y += resettable.o
>>   common-obj-$(CONFIG_SOFTMMU) += qdev-fw.o
>>   common-obj-$(CONFIG_SOFTMMU) += fw-path-provider.o
>>   # irq.o needed for qdev GPIO handling:
>> diff --git a/hw/core/trace-events b/hw/core/trace-events
>> index a375aa88a4..a2e43f1120 100644
>> --- a/hw/core/trace-events
>> +++ b/hw/core/trace-events
>> @@ -9,3 +9,20 @@ qbus_reset(void *obj, const char *objtype) "obj=%p(%s)"
>>   qbus_reset_all(void *obj, const char *objtype) "obj=%p(%s)"
>>   qbus_reset_tree(void *obj, const char *objtype) "obj=%p(%s)"
>>   qdev_update_parent_bus(void *obj, const char *objtype, void *oldp,
>> const char *oldptype, void *newp, const char *newptype) "obj=%p(%s)
>> old_parent=%p(%s) new_parent=%p(%s)"
>> +
>> +# resettable.c
>> +resettable_reset(void *obj, int cold) "obj=%p cold=%d"
>> +resettable_reset_assert_begin(void *obj, int cold) "obj=%p cold=%d"
>> +resettable_reset_assert_end(void *obj) "obj=%p"
>> +resettable_reset_release_begin(void *obj, int cold) "obj=%p cold=%d"
>> +resettable_reset_release_end(void *obj) "obj=%p"
>> +resettable_phase_enter_begin(void *obj, const char *objtype, uint32_t
>> count, int type) "obj=%p(%s) count=%" PRIu32 " type=%d"
>> +resettable_phase_enter_exec(void *obj, const char *objtype, int type,
>> int has_method) "obj=%p(%s) type=%d method=%d"
>> +resettable_phase_enter_end(void *obj, const char *objtype, uint32_t
>> count) "obj=%p(%s) count=%" PRIu32
>> +resettable_phase_hold_begin(void *obj, const char *objtype, uint32_t
>> count, int type) "obj=%p(%s) count=%" PRIu32 " type=%d"
>> +resettable_phase_hold_exec(void *obj, const char *objtype, int
>> has_method) "obj=%p(%s) method=%d"
>> +resettable_phase_hold_end(void *obj, const char *objtype, uint32_t
>> count) "obj=%p(%s) count=%" PRIu32
>> +resettable_phase_exit_begin(void *obj, const char *objtype, uint32_t
>> count, int type) "obj=%p(%s) count=%" PRIu32 " type=%d"
>> +resettable_phase_exit_exec(void *obj, const char *objtype, int
>> has_method) "obj=%p(%s) method=%d"
>> +resettable_phase_exit_end(void *obj, const char *objtype, uint32_t
>> count) "obj=%p(%s) count=%" PRIu32
>> +resettable_transitional_function(void *obj, const char *objtype)
>> "obj=%p(%s)"
>>
> 

Re: [PATCH v7 03/11] hw/core: create Resettable QOM interface

[Damien Hedde]

On 1/18/20 7:42 AM, Philippe Mathieu-Daudé wrote:
> On 1/15/20 1:36 PM, Damien Hedde wrote:
>> This commit defines an interface allowing multi-phase reset. This aims
>> to solve a problem of the actual single-phase reset (built in
>> DeviceClass and BusClass): reset behavior is dependent on the order
>> in which reset handlers are called. In particular doing external
>> side-effect (like setting an qemu_irq) is problematic because receiving
>> object may not be reset yet.
>>
>> The Resettable interface divides the reset in 3 well defined phases.
>> To reset an object tree, all 1st phases are executed then all 2nd then
>> all 3rd. See the comments in include/hw/resettable.h for a more complete
>> description. The interface defines 3 phases to let the future
>> possibility of holding an object into reset for some time.
>>
>> The qdev/qbus reset in DeviceClass and BusClass will be modified in
>> following commits to use this interface. A mechanism is provided
>> to allow executing a transitional reset handler in place of the 2nd
>> phase which is executed in children-then-parent order inside a tree.
>> This will allow to transition devices and buses smoothly while
>> keeping the exact current qdev/qbus reset behavior for now.
>>
>> Documentation will be added in a following commit.
>>
>> Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
>> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
>> ---
>>
>> v7 update: un-nest struct ResettablePhases
>> ---
>>   Makefile.objs           |   1 +
>>   include/hw/resettable.h | 211 +++++++++++++++++++++++++++++++++++
>>   hw/core/resettable.c    | 238 ++++++++++++++++++++++++++++++++++++++++
>>   hw/core/Makefile.objs   |   1 +
>>   hw/core/trace-events    |  17 +++
>>   5 files changed, 468 insertions(+)
>>   create mode 100644 include/hw/resettable.h
>>   create mode 100644 hw/core/resettable.c
>>
>> diff --git a/Makefile.objs b/Makefile.objs
>> index 7c1e50f9d6..9752d549b4 100644
>> --- a/Makefile.objs
>> +++ b/Makefile.objs
>> @@ -191,6 +191,7 @@ trace-events-subdirs += migration
>>   trace-events-subdirs += net
>>   trace-events-subdirs += ui
>>   endif
>> +trace-events-subdirs += hw/core
>>   trace-events-subdirs += hw/display
>>   trace-events-subdirs += qapi
>>   trace-events-subdirs += qom
>> diff --git a/include/hw/resettable.h b/include/hw/resettable.h
>> new file mode 100644
>> index 0000000000..58b3df4c22
>> --- /dev/null
>> +++ b/include/hw/resettable.h
>> @@ -0,0 +1,211 @@
>> +/*
>> + * Resettable interface header.
>> + *
>> + * Copyright (c) 2019 GreenSocs SAS
>> + *
>> + * Authors:
>> + *   Damien Hedde
>> + *
>> + * This work is licensed under the terms of the GNU GPL, version 2 or
>> later.
>> + * See the COPYING file in the top-level directory.
>> + */
>> +
>> +#ifndef HW_RESETTABLE_H
>> +#define HW_RESETTABLE_H
>> +
>> +#include "qom/object.h"
>> +
>> +#define TYPE_RESETTABLE_INTERFACE "resettable"
>> +
>> +#define RESETTABLE_CLASS(class) \
>> +    OBJECT_CLASS_CHECK(ResettableClass, (class),
>> TYPE_RESETTABLE_INTERFACE)
>> +
>> +#define RESETTABLE_GET_CLASS(obj) \
>> +    OBJECT_GET_CLASS(ResettableClass, (obj), TYPE_RESETTABLE_INTERFACE)
>> +
>> +typedef struct ResettableState ResettableState;
>> +
>> +/**
>> + * ResetType:
>> + * Types of reset.
>> + *
>> + * + Cold: reset resulting from a power cycle of the object.
>> + *
>> + * TODO: Support has to be added to handle more types. In particular,
>> + * ResettableState structure needs to be expanded.
>> + */
>> +typedef enum ResetType {
>> +    RESET_TYPE_COLD,
>> +} ResetType;
>> +
>> +/*
>> + * ResettableClass:
>> + * Interface for resettable objects.
>> + *
>> + * See docs/devel/reset.rst for more detailed information about how
>> QEMU models
>> + * reset. This whole API must only be used when holding the iothread
>> mutex.
>> + *
>> + * All objects which can be reset must implement this interface;
>> + * it is usually provided by a base class such as DeviceClass or
>> BusClass.
>> + * Every Resettable object must maintain some state tracking the
>> + * progress of a reset operation by providing a ResettableState
>> structure.
>> + * The functions defined in this module take care of updating the
>> + * state of the reset.
>> + * The base class implementation of the interface provides this
>> + * state and implements the associated method: get_state.
>> + *
>> + * Concrete object implementations (typically specific devices
>> + * such as a UART model) should provide the functions
>> + * for the phases.enter, phases.hold and phases.exit methods, which
>> + * they can set in their class init function, either directly or
>> + * by calling resettable_class_set_parent_phases().
>> + * The phase methods are guaranteed to only only ever be called once
>> + * for any reset event, in the order 'enter', 'hold', 'exit'.
>> + * An object will always move quickly from 'enter' to 'hold'
>> + * but might remain in 'hold' for an arbitrary period of time
>> + * before eventually reset is deasserted and the 'exit' phase is called.
>> + * Object implementations should be prepared for functions handling
>> + * inbound connections from other devices (such as qemu_irq handler
>> + * functions) to be called at any point during reset after their
>> + * 'enter' method has been called.
>> + *
>> + * Users of a resettable object should not call these methods
>> + * directly, but instead use the function resettable_reset().
>> + *
>> + * @phases.enter: This phase is called when the object enters reset. It
>> + * should reset local state of the object, but it must not do
>> anything that
>> + * has a side-effect on other objects, such as raising or lowering a
>> qemu_irq
>> + * line or reading or writing guest memory. It takes the reset's type as
>> + * argument.
>> + *
>> + * @phases.hold: This phase is called for entry into reset, once
>> every object
>> + * in the system which is being reset has had its @phases.enter
>> method called.
>> + * At this point devices can do actions that affect other objects.
>> + *
>> + * @phases.exit: This phase is called when the object leaves the
>> reset state.
>> + * Actions affecting other objects are permitted.
>> + *
>> + * @get_state: Mandatory method which must return a pointer to a
>> + * ResettableState.
>> + *
>> + * @get_transitional_function: transitional method to handle
>> Resettable objects
>> + * not yet fully moved to this interface. It will be removed as soon
>> as it is
>> + * not needed anymore. This method is optional and may return a
>> pointer to a
>> + * function to be used instead of the phases. If the method exists
>> and returns
>> + * a non-NULL function pointer then that function is executed as a
>> replacement
>> + * of the 'hold' phase method taking the object as argument. The two
>> other phase
>> + * methods are not executed.
>> + *
>> + * @child_foreach: Executes a given callback on every Resettable
>> child. Child
>> + * in this context means a child in the qbus tree, so the children of
>> a qbus
>> + * are the devices on it, and the children of a device are all the
>> buses it
>> + * owns. This is not the same as the QOM object hierarchy. The
>> function takes
>> + * additional opaque and ResetType arguments which must be passed
>> unmodified to
>> + * the callback.
>> + */
>> +typedef void (*ResettableEnterPhase)(Object *obj, ResetType type);
>> +typedef void (*ResettableHoldPhase)(Object *obj);
>> +typedef void (*ResettableExitPhase)(Object *obj);
>> +typedef ResettableState * (*ResettableGetState)(Object *obj);
>> +typedef void (*ResettableTrFunction)(Object *obj);
>> +typedef ResettableTrFunction (*ResettableGetTrFunction)(Object *obj);
>> +typedef void (*ResettableChildCallback)(Object *, void *opaque,
>> +                                        ResetType type);
>> +typedef void (*ResettableChildForeach)(Object *obj,
>> +                                       ResettableChildCallback cb,
>> +                                       void *opaque, ResetType type);
>> +typedef struct ResettablePhases {
>> +    ResettableEnterPhase enter;
>> +    ResettableHoldPhase hold;
>> +    ResettableExitPhase exit;
>> +} ResettablePhases;
>> +typedef struct ResettableClass {
>> +    InterfaceClass parent_class;
>> +
>> +    /* Phase methods */
>> +    ResettablePhases phases;
>> +
>> +    /* State access method */
>> +    ResettableGetState get_state;
>> +
>> +    /* Transitional method for legacy reset compatibility */
>> +    ResettableGetTrFunction get_transitional_function;
>> +
>> +    /* Hierarchy handling method */
>> +    ResettableChildForeach child_foreach;
>> +} ResettableClass;
>> +
>> +/**
>> + * ResettableState:
>> + * Structure holding reset related state. The fields should not be
>> accessed
>> + * directly; the definition is here to allow further inclusion into
>> other
>> + * objects.
>> + *
>> + * @count: Number of reset level the object is into. It is
>> incremented when
>> + * the reset operation starts and decremented when it finishes.
> 
> Maybe you can add this comment and the variable in patch 5/11, that
> would make patch 5 easier to review.

The variable is used in this patch so I cannot do that.

> 
>> + * @hold_phase_pending: flag which indicates that we need to invoke
>> the 'hold'
>> + * phase handler for this object.
>> + * @exit_phase_in_progress: true if we are currently in the exit phase
>> + */
>> +struct ResettableState {
>> +    uint32_t count;
> 
> Maybe simply 'unsigned'?
> 

Ok.

--
Damien

Re: [PATCH v7 03/11] hw/core: create Resettable QOM interface

[Philippe Mathieu-Daudé]

On 1/20/20 10:08 AM, Damien Hedde wrote:
> On 1/18/20 7:42 AM, Philippe Mathieu-Daudé wrote:
>> On 1/15/20 1:36 PM, Damien Hedde wrote:
>>> This commit defines an interface allowing multi-phase reset. This aims
>>> to solve a problem of the actual single-phase reset (built in
>>> DeviceClass and BusClass): reset behavior is dependent on the order
>>> in which reset handlers are called. In particular doing external
>>> side-effect (like setting an qemu_irq) is problematic because receiving
>>> object may not be reset yet.
>>>
>>> The Resettable interface divides the reset in 3 well defined phases.
>>> To reset an object tree, all 1st phases are executed then all 2nd then
>>> all 3rd. See the comments in include/hw/resettable.h for a more complete
>>> description. The interface defines 3 phases to let the future
>>> possibility of holding an object into reset for some time.
>>>
>>> The qdev/qbus reset in DeviceClass and BusClass will be modified in
>>> following commits to use this interface. A mechanism is provided
>>> to allow executing a transitional reset handler in place of the 2nd
>>> phase which is executed in children-then-parent order inside a tree.
>>> This will allow to transition devices and buses smoothly while
>>> keeping the exact current qdev/qbus reset behavior for now.
>>>
>>> Documentation will be added in a following commit.
>>>
>>> Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
>>> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
>>> ---
>>>
>>> v7 update: un-nest struct ResettablePhases
>>> ---
>>>    Makefile.objs           |   1 +
>>>    include/hw/resettable.h | 211 +++++++++++++++++++++++++++++++++++
>>>    hw/core/resettable.c    | 238 ++++++++++++++++++++++++++++++++++++++++
>>>    hw/core/Makefile.objs   |   1 +
>>>    hw/core/trace-events    |  17 +++
>>>    5 files changed, 468 insertions(+)
>>>    create mode 100644 include/hw/resettable.h
>>>    create mode 100644 hw/core/resettable.c
>>>
>>> diff --git a/Makefile.objs b/Makefile.objs
>>> index 7c1e50f9d6..9752d549b4 100644
>>> --- a/Makefile.objs
>>> +++ b/Makefile.objs
>>> @@ -191,6 +191,7 @@ trace-events-subdirs += migration
>>>    trace-events-subdirs += net
>>>    trace-events-subdirs += ui
>>>    endif
>>> +trace-events-subdirs += hw/core
>>>    trace-events-subdirs += hw/display
>>>    trace-events-subdirs += qapi
>>>    trace-events-subdirs += qom
>>> diff --git a/include/hw/resettable.h b/include/hw/resettable.h
>>> new file mode 100644
>>> index 0000000000..58b3df4c22
>>> --- /dev/null
>>> +++ b/include/hw/resettable.h
>>> @@ -0,0 +1,211 @@
>>> +/*
>>> + * Resettable interface header.
>>> + *
>>> + * Copyright (c) 2019 GreenSocs SAS
>>> + *
>>> + * Authors:
>>> + *   Damien Hedde
>>> + *
>>> + * This work is licensed under the terms of the GNU GPL, version 2 or
>>> later.
>>> + * See the COPYING file in the top-level directory.
>>> + */
>>> +
>>> +#ifndef HW_RESETTABLE_H
>>> +#define HW_RESETTABLE_H
>>> +
>>> +#include "qom/object.h"
>>> +
>>> +#define TYPE_RESETTABLE_INTERFACE "resettable"
>>> +
>>> +#define RESETTABLE_CLASS(class) \
>>> +    OBJECT_CLASS_CHECK(ResettableClass, (class),
>>> TYPE_RESETTABLE_INTERFACE)
>>> +
>>> +#define RESETTABLE_GET_CLASS(obj) \
>>> +    OBJECT_GET_CLASS(ResettableClass, (obj), TYPE_RESETTABLE_INTERFACE)
>>> +
>>> +typedef struct ResettableState ResettableState;
>>> +
>>> +/**
>>> + * ResetType:
>>> + * Types of reset.
>>> + *
>>> + * + Cold: reset resulting from a power cycle of the object.
>>> + *
>>> + * TODO: Support has to be added to handle more types. In particular,
>>> + * ResettableState structure needs to be expanded.
>>> + */
>>> +typedef enum ResetType {
>>> +    RESET_TYPE_COLD,
>>> +} ResetType;
>>> +
>>> +/*
>>> + * ResettableClass:
>>> + * Interface for resettable objects.
>>> + *
>>> + * See docs/devel/reset.rst for more detailed information about how
>>> QEMU models
>>> + * reset. This whole API must only be used when holding the iothread
>>> mutex.
>>> + *
>>> + * All objects which can be reset must implement this interface;
>>> + * it is usually provided by a base class such as DeviceClass or
>>> BusClass.
>>> + * Every Resettable object must maintain some state tracking the
>>> + * progress of a reset operation by providing a ResettableState
>>> structure.
>>> + * The functions defined in this module take care of updating the
>>> + * state of the reset.
>>> + * The base class implementation of the interface provides this
>>> + * state and implements the associated method: get_state.
>>> + *
>>> + * Concrete object implementations (typically specific devices
>>> + * such as a UART model) should provide the functions
>>> + * for the phases.enter, phases.hold and phases.exit methods, which
>>> + * they can set in their class init function, either directly or
>>> + * by calling resettable_class_set_parent_phases().
>>> + * The phase methods are guaranteed to only only ever be called once
>>> + * for any reset event, in the order 'enter', 'hold', 'exit'.
>>> + * An object will always move quickly from 'enter' to 'hold'
>>> + * but might remain in 'hold' for an arbitrary period of time
>>> + * before eventually reset is deasserted and the 'exit' phase is called.
>>> + * Object implementations should be prepared for functions handling
>>> + * inbound connections from other devices (such as qemu_irq handler
>>> + * functions) to be called at any point during reset after their
>>> + * 'enter' method has been called.
>>> + *
>>> + * Users of a resettable object should not call these methods
>>> + * directly, but instead use the function resettable_reset().
>>> + *
>>> + * @phases.enter: This phase is called when the object enters reset. It
>>> + * should reset local state of the object, but it must not do
>>> anything that
>>> + * has a side-effect on other objects, such as raising or lowering a
>>> qemu_irq
>>> + * line or reading or writing guest memory. It takes the reset's type as
>>> + * argument.
>>> + *
>>> + * @phases.hold: This phase is called for entry into reset, once
>>> every object
>>> + * in the system which is being reset has had its @phases.enter
>>> method called.
>>> + * At this point devices can do actions that affect other objects.
>>> + *
>>> + * @phases.exit: This phase is called when the object leaves the
>>> reset state.
>>> + * Actions affecting other objects are permitted.
>>> + *
>>> + * @get_state: Mandatory method which must return a pointer to a
>>> + * ResettableState.
>>> + *
>>> + * @get_transitional_function: transitional method to handle
>>> Resettable objects
>>> + * not yet fully moved to this interface. It will be removed as soon
>>> as it is
>>> + * not needed anymore. This method is optional and may return a
>>> pointer to a
>>> + * function to be used instead of the phases. If the method exists
>>> and returns
>>> + * a non-NULL function pointer then that function is executed as a
>>> replacement
>>> + * of the 'hold' phase method taking the object as argument. The two
>>> other phase
>>> + * methods are not executed.
>>> + *
>>> + * @child_foreach: Executes a given callback on every Resettable
>>> child. Child
>>> + * in this context means a child in the qbus tree, so the children of
>>> a qbus
>>> + * are the devices on it, and the children of a device are all the
>>> buses it
>>> + * owns. This is not the same as the QOM object hierarchy. The
>>> function takes
>>> + * additional opaque and ResetType arguments which must be passed
>>> unmodified to
>>> + * the callback.
>>> + */
>>> +typedef void (*ResettableEnterPhase)(Object *obj, ResetType type);
>>> +typedef void (*ResettableHoldPhase)(Object *obj);
>>> +typedef void (*ResettableExitPhase)(Object *obj);
>>> +typedef ResettableState * (*ResettableGetState)(Object *obj);
>>> +typedef void (*ResettableTrFunction)(Object *obj);
>>> +typedef ResettableTrFunction (*ResettableGetTrFunction)(Object *obj);
>>> +typedef void (*ResettableChildCallback)(Object *, void *opaque,
>>> +                                        ResetType type);
>>> +typedef void (*ResettableChildForeach)(Object *obj,
>>> +                                       ResettableChildCallback cb,
>>> +                                       void *opaque, ResetType type);
>>> +typedef struct ResettablePhases {
>>> +    ResettableEnterPhase enter;
>>> +    ResettableHoldPhase hold;
>>> +    ResettableExitPhase exit;
>>> +} ResettablePhases;
>>> +typedef struct ResettableClass {
>>> +    InterfaceClass parent_class;
>>> +
>>> +    /* Phase methods */
>>> +    ResettablePhases phases;
>>> +
>>> +    /* State access method */
>>> +    ResettableGetState get_state;
>>> +
>>> +    /* Transitional method for legacy reset compatibility */
>>> +    ResettableGetTrFunction get_transitional_function;
>>> +
>>> +    /* Hierarchy handling method */
>>> +    ResettableChildForeach child_foreach;
>>> +} ResettableClass;
>>> +
>>> +/**
>>> + * ResettableState:
>>> + * Structure holding reset related state. The fields should not be
>>> accessed
>>> + * directly; the definition is here to allow further inclusion into
>>> other
>>> + * objects.
>>> + *
>>> + * @count: Number of reset level the object is into. It is
>>> incremented when
>>> + * the reset operation starts and decremented when it finishes.
>>
>> Maybe you can add this comment and the variable in patch 5/11, that
>> would make patch 5 easier to review.
> 
> The variable is used in this patch so I cannot do that.

Oops you are right o_O ...

>>
>>> + * @hold_phase_pending: flag which indicates that we need to invoke
>>> the 'hold'
>>> + * phase handler for this object.
>>> + * @exit_phase_in_progress: true if we are currently in the exit phase
>>> + */
>>> +struct ResettableState {
>>> +    uint32_t count;
>>
>> Maybe simply 'unsigned'?
>>
> 
> Ok.
> 
> --
> Damien