[Qemu-devel] [PATCH RFC V2 0/8] virtio: migrate new properties

[Qemu-devel] [PATCH RFC V2 0/8] virtio: migrate new properties

[Greg Kurz]

Hi,

This patch set tries to address comments from the initial
review. For this round, I have focused on two changes:
- as suggested by Andreas, we now call the device specific
  code from the generic code to ease the implementation of
  future devices. This is achieved with the addition of
  load/save methods to VirtioDeviceClass.
- virtio subsections now implement a "needed" concept with
  the same semantics as in the VMState code.

I haven't looked at compat mode issues yet, but it is
on my TODO list.

Cheers.

---

Greg Kurz (8):
      virtio: introduce device specific migration calls
      virtio-net: implement per-device migration calls
      virtio-blk: implement per-device migration calls
      virtio-serial: implement per-device migration calls
      virtio-balloon: implement per-device migration calls
      virtio-rng: implement per-device migration calls
      virtio: add subsections to the migration stream
      virtio: add endian-ambivalent support to VirtIODevice


 exec.c                      |    8 --
 hw/block/virtio-blk.c       |   24 ++++--
 hw/char/virtio-serial-bus.c |   32 +++++---
 hw/net/virtio-net.c         |   22 ++++--
 hw/scsi/virtio-scsi.c       |    2 -
 hw/virtio/virtio-balloon.c  |   25 ++++--
 hw/virtio/virtio-pci.c      |   11 +--
 hw/virtio/virtio-rng.c      |   12 ++-
 hw/virtio/virtio.c          |  169 ++++++++++++++++++++++++++++++++++++++++---
 include/exec/cpu-common.h   |    1 
 include/hw/virtio/virtio.h  |   17 ++++
 11 files changed, 251 insertions(+), 72 deletions(-)

-- 
Greg

[Qemu-devel] [PATCH RFC 1/8] virtio: introduce device specific migration calls

[Greg Kurz]

In order to migrate virtio subsections, we need the device specific
code to be called from the common migration code. This patch introduces
load and save methods for this purpose.

Suggested-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
---
 hw/block/virtio-blk.c       |    2 +-
 hw/char/virtio-serial-bus.c |    2 +-
 hw/net/virtio-net.c         |    2 +-
 hw/scsi/virtio-scsi.c       |    2 +-
 hw/virtio/virtio-balloon.c  |    2 +-
 hw/virtio/virtio-rng.c      |    2 +-
 hw/virtio/virtio.c          |   13 ++++++++++++-
 include/hw/virtio/virtio.h  |    4 +++-
 8 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index 8a568e5..63d4ccd 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -611,7 +611,7 @@ static int virtio_blk_load(QEMUFile *f, void *opaque, int version_id)
     if (version_id != 2)
         return -EINVAL;
 
-    ret = virtio_load(vdev, f);
+    ret = virtio_load(vdev, f, version_id);
     if (ret) {
         return ret;
     }
diff --git a/hw/char/virtio-serial-bus.c b/hw/char/virtio-serial-bus.c
index 2b647b6..b0f322a 100644
--- a/hw/char/virtio-serial-bus.c
+++ b/hw/char/virtio-serial-bus.c
@@ -676,7 +676,7 @@ static int virtio_serial_load(QEMUFile *f, void *opaque, int version_id)
     }
 
     /* The virtio device */
-    ret = virtio_load(VIRTIO_DEVICE(s), f);
+    ret = virtio_load(VIRTIO_DEVICE(s), f, version_id);
     if (ret) {
         return ret;
     }
diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index fd23c46..e0dc544 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -1311,7 +1311,7 @@ static int virtio_net_load(QEMUFile *f, void *opaque, int version_id)
     if (version_id < 2 || version_id > VIRTIO_NET_VM_VERSION)
         return -EINVAL;
 
-    ret = virtio_load(vdev, f);
+    ret = virtio_load(vdev, f, version_id);
     if (ret) {
         return ret;
     }
diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
index b0d7517..e82e66d 100644
--- a/hw/scsi/virtio-scsi.c
+++ b/hw/scsi/virtio-scsi.c
@@ -478,7 +478,7 @@ static int virtio_scsi_load(QEMUFile *f, void *opaque, int version_id)
     VirtIODevice *vdev = VIRTIO_DEVICE(opaque);
     int ret;
 
-    ret = virtio_load(vdev, f);
+    ret = virtio_load(vdev, f, version_id);
     if (ret) {
         return ret;
     }
diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
index a470a0b..6d8ec72 100644
--- a/hw/virtio/virtio-balloon.c
+++ b/hw/virtio/virtio-balloon.c
@@ -327,7 +327,7 @@ static int virtio_balloon_load(QEMUFile *f, void *opaque, int version_id)
     if (version_id != 1)
         return -EINVAL;
 
-    ret = virtio_load(vdev, f);
+    ret = virtio_load(vdev, f, version_id);
     if (ret) {
         return ret;
     }
diff --git a/hw/virtio/virtio-rng.c b/hw/virtio/virtio-rng.c
index b6ab361..025de81 100644
--- a/hw/virtio/virtio-rng.c
+++ b/hw/virtio/virtio-rng.c
@@ -113,7 +113,7 @@ static int virtio_rng_load(QEMUFile *f, void *opaque, int version_id)
     if (version_id != 1) {
         return -EINVAL;
     }
-    virtio_load(vdev, f);
+    virtio_load(vdev, f, version_id);
 
     /* We may have an element ready but couldn't process it due to a quota
      * limit.  Make sure to try again after live migration when the quota may
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index aeabf3a..cf87b44 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -837,6 +837,7 @@ void virtio_save(VirtIODevice *vdev, QEMUFile *f)
 {
     BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
+    VirtioDeviceClass *vdc = VIRTIO_DEVICE_GET_CLASS(vdev);
     int i;
 
     if (k->save_config) {
@@ -871,6 +872,10 @@ void virtio_save(VirtIODevice *vdev, QEMUFile *f)
             k->save_queue(qbus->parent, i, f);
         }
     }
+
+    if (vdc->save != NULL) {
+        vdc->save(vdev, f);
+    }
 }
 
 int virtio_set_features(VirtIODevice *vdev, uint32_t val)
@@ -889,13 +894,14 @@ int virtio_set_features(VirtIODevice *vdev, uint32_t val)
     return bad ? -1 : 0;
 }
 
-int virtio_load(VirtIODevice *vdev, QEMUFile *f)
+int virtio_load(VirtIODevice *vdev, QEMUFile *f, int version_id)
 {
     int num, i, ret;
     uint32_t features;
     uint32_t supported_features;
     BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
+    VirtioDeviceClass *vdc = VIRTIO_DEVICE_GET_CLASS(vdev);
 
     if (k->load_config) {
         ret = k->load_config(qbus->parent, f);
@@ -956,6 +962,11 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f)
     }
 
     virtio_notify_vector(vdev, VIRTIO_NO_VECTOR);
+
+    if (vdc->load != NULL) {
+        return vdc->load(vdev, f, version_id);
+    }
+
     return 0;
 }
 
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index 3e54e90..3505ce5 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -150,6 +150,8 @@ typedef struct VirtioDeviceClass {
      * must mask in frontend instead.
      */
     void (*guest_notifier_mask)(VirtIODevice *vdev, int n, bool mask);
+    void (*save)(VirtIODevice *vdev, QEMUFile *f);
+    int (*load)(VirtIODevice *vdev, QEMUFile *f, int version_id);
 } VirtioDeviceClass;
 
 void virtio_init(VirtIODevice *vdev, const char *name,
@@ -184,7 +186,7 @@ void virtio_notify(VirtIODevice *vdev, VirtQueue *vq);
 
 void virtio_save(VirtIODevice *vdev, QEMUFile *f);
 
-int virtio_load(VirtIODevice *vdev, QEMUFile *f);
+int virtio_load(VirtIODevice *vdev, QEMUFile *f, int version_id);
 
 void virtio_notify_config(VirtIODevice *vdev);
 

[Qemu-devel] [PATCH RFC 2/8] virtio-net: implement per-device migration calls

[Greg Kurz]

Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
---
 hw/net/virtio-net.c |   22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index e0dc544..d319ac2 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -1263,7 +1263,6 @@ static void virtio_net_set_multiqueue(VirtIONet *n, int multiqueue)
 
 static void virtio_net_save(QEMUFile *f, void *opaque)
 {
-    int i;
     VirtIONet *n = opaque;
     VirtIODevice *vdev = VIRTIO_DEVICE(n);
 
@@ -1271,6 +1270,12 @@ static void virtio_net_save(QEMUFile *f, void *opaque)
      * it might keep writing to memory. */
     assert(!n->vhost_started);
     virtio_save(vdev, f);
+}
+
+static void virtio_net_save_device(VirtIODevice *vdev, QEMUFile *f)
+{
+    VirtIONet *n = VIRTIO_NET(vdev);
+    int i;
 
     qemu_put_buffer(f, n->mac, ETH_ALEN);
     qemu_put_be32(f, n->vqs[0].tx_waiting);
@@ -1306,15 +1311,18 @@ static int virtio_net_load(QEMUFile *f, void *opaque, int version_id)
 {
     VirtIONet *n = opaque;
     VirtIODevice *vdev = VIRTIO_DEVICE(n);
-    int ret, i, link_down;
 
     if (version_id < 2 || version_id > VIRTIO_NET_VM_VERSION)
         return -EINVAL;
 
-    ret = virtio_load(vdev, f, version_id);
-    if (ret) {
-        return ret;
-    }
+    return virtio_load(vdev, f, version_id);
+}
+
+static int virtio_net_load_device(VirtIODevice *vdev, QEMUFile *f,
+                                  int version_id)
+{
+    VirtIONet *n = VIRTIO_NET(vdev);
+    int i, link_down;
 
     qemu_get_buffer(f, n->mac, ETH_ALEN);
     n->vqs[0].tx_waiting = qemu_get_be32(f);
@@ -1651,6 +1659,8 @@ static void virtio_net_class_init(ObjectClass *klass, void *data)
     vdc->set_status = virtio_net_set_status;
     vdc->guest_notifier_mask = virtio_net_guest_notifier_mask;
     vdc->guest_notifier_pending = virtio_net_guest_notifier_pending;
+    vdc->load = virtio_net_load_device;
+    vdc->save = virtio_net_save_device;
 }
 
 static const TypeInfo virtio_net_info = {

[Qemu-devel] [PATCH RFC 3/8] virtio-blk: implement per-device migration calls

[Greg Kurz]

Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
---
 hw/block/virtio-blk.c |   24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index 63d4ccd..a50be54 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -588,12 +588,16 @@ static void virtio_blk_set_status(VirtIODevice *vdev, uint8_t status)
 
 static void virtio_blk_save(QEMUFile *f, void *opaque)
 {
-    VirtIOBlock *s = opaque;
-    VirtIODevice *vdev = VIRTIO_DEVICE(s);
-    VirtIOBlockReq *req = s->rq;
+    VirtIODevice *vdev = VIRTIO_DEVICE(opaque);
 
     virtio_save(vdev, f);
+}
     
+static void virtio_blk_save_device(VirtIODevice *vdev, QEMUFile *f)
+{
+    VirtIOBlock *s = VIRTIO_BLK(vdev);
+    VirtIOBlockReq *req = s->rq;
+
     while (req) {
         qemu_put_sbyte(f, 1);
         qemu_put_buffer(f, (unsigned char*)&req->elem, sizeof(req->elem));
@@ -606,15 +610,17 @@ static int virtio_blk_load(QEMUFile *f, void *opaque, int version_id)
 {
     VirtIOBlock *s = opaque;
     VirtIODevice *vdev = VIRTIO_DEVICE(s);
-    int ret;
 
     if (version_id != 2)
         return -EINVAL;
 
-    ret = virtio_load(vdev, f, version_id);
-    if (ret) {
-        return ret;
-    }
+    return virtio_load(vdev, f, version_id);
+}
+
+static int virtio_blk_load_device(VirtIODevice *vdev, QEMUFile *f,
+                                  int version_id)
+{
+    VirtIOBlock *s = VIRTIO_BLK(vdev);
 
     while (qemu_get_sbyte(f)) {
         VirtIOBlockReq *req = virtio_blk_alloc_request(s);
@@ -773,6 +779,8 @@ static void virtio_blk_class_init(ObjectClass *klass, void *data)
     vdc->get_features = virtio_blk_get_features;
     vdc->set_status = virtio_blk_set_status;
     vdc->reset = virtio_blk_reset;
+    vdc->save = virtio_blk_save_device;
+    vdc->load = virtio_blk_load_device;
 }
 
 static const TypeInfo virtio_device_info = {

[Qemu-devel] [PATCH RFC 4/8] virtio-serial: implement per-device migration calls

[Greg Kurz]

Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
---
 hw/char/virtio-serial-bus.c |   32 +++++++++++++++++++-------------
 1 file changed, 19 insertions(+), 13 deletions(-)

diff --git a/hw/char/virtio-serial-bus.c b/hw/char/virtio-serial-bus.c
index b0f322a..ce336a0 100644
--- a/hw/char/virtio-serial-bus.c
+++ b/hw/char/virtio-serial-bus.c
@@ -521,14 +521,17 @@ static void vser_reset(VirtIODevice *vdev)
 
 static void virtio_serial_save(QEMUFile *f, void *opaque)
 {
-    VirtIOSerial *s = VIRTIO_SERIAL(opaque);
+    /* The virtio device */
+    virtio_save(VIRTIO_DEVICE(opaque), f);
+}
+
+static void virtio_serial_save_device(VirtIODevice *vdev, QEMUFile *f)
+{
+    VirtIOSerial *s = VIRTIO_SERIAL(vdev);
     VirtIOSerialPort *port;
     uint32_t nr_active_ports;
     unsigned int i, max_nr_ports;
 
-    /* The virtio device */
-    virtio_save(VIRTIO_DEVICE(s), f);
-
     /* The config space */
     qemu_put_be16s(f, &s->config.cols);
     qemu_put_be16s(f, &s->config.rows);
@@ -666,20 +669,21 @@ static int fetch_active_ports_list(QEMUFile *f, int version_id,
 
 static int virtio_serial_load(QEMUFile *f, void *opaque, int version_id)
 {
-    VirtIOSerial *s = VIRTIO_SERIAL(opaque);
-    uint32_t max_nr_ports, nr_active_ports, ports_map;
-    unsigned int i;
-    int ret;
-
     if (version_id > 3) {
         return -EINVAL;
     }
 
     /* The virtio device */
-    ret = virtio_load(VIRTIO_DEVICE(s), f, version_id);
-    if (ret) {
-        return ret;
-    }
+    return virtio_load(VIRTIO_DEVICE(opaque), f, version_id);
+}
+
+static int virtio_serial_load_device(VirtIODevice *vdev, QEMUFile *f,
+                                     int version_id)
+{
+    VirtIOSerial *s = VIRTIO_SERIAL(vdev);
+    uint32_t max_nr_ports, nr_active_ports, ports_map;
+    unsigned int i;
+    int ret;
 
     if (version_id < 2) {
         return 0;
@@ -1027,6 +1031,8 @@ static void virtio_serial_class_init(ObjectClass *klass, void *data)
     vdc->set_config = set_config;
     vdc->set_status = set_status;
     vdc->reset = vser_reset;
+    vdc->save = virtio_serial_save_device;
+    vdc->load = virtio_serial_load_device;
 }
 
 static const TypeInfo virtio_device_info = {

[Qemu-devel] [PATCH RFC 5/8] virtio-balloon: implement per-device migration calls

[Greg Kurz]

Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
---
 hw/virtio/virtio-balloon.c |   25 ++++++++++++++-----------
 1 file changed, 14 insertions(+), 11 deletions(-)

diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
index 6d8ec72..a3a9ac1 100644
--- a/hw/virtio/virtio-balloon.c
+++ b/hw/virtio/virtio-balloon.c
@@ -309,10 +309,12 @@ static void virtio_balloon_to_target(void *opaque, ram_addr_t target)
 
 static void virtio_balloon_save(QEMUFile *f, void *opaque)
 {
-    VirtIOBalloon *s = VIRTIO_BALLOON(opaque);
-    VirtIODevice *vdev = VIRTIO_DEVICE(s);
+    virtio_save(VIRTIO_DEVICE(opaque), f);
+}
 
-    virtio_save(vdev, f);
+static void virtio_balloon_save_device(VirtIODevice *vdev, QEMUFile *f)
+{
+    VirtIOBalloon *s = VIRTIO_BALLOON(vdev);
 
     qemu_put_be32(f, s->num_pages);
     qemu_put_be32(f, s->actual);
@@ -320,17 +322,16 @@ static void virtio_balloon_save(QEMUFile *f, void *opaque)
 
 static int virtio_balloon_load(QEMUFile *f, void *opaque, int version_id)
 {
-    VirtIOBalloon *s = VIRTIO_BALLOON(opaque);
-    VirtIODevice *vdev = VIRTIO_DEVICE(s);
-    int ret;
-
     if (version_id != 1)
         return -EINVAL;
 
-    ret = virtio_load(vdev, f, version_id);
-    if (ret) {
-        return ret;
-    }
+    return virtio_load(VIRTIO_DEVICE(opaque), f, version_id);
+}
+
+static int virtio_balloon_load_device(VirtIODevice *vdev, QEMUFile *f,
+                                      int version_id)
+{
+    VirtIOBalloon *s = VIRTIO_BALLOON(vdev);
 
     s->num_pages = qemu_get_be32(f);
     s->actual = qemu_get_be32(f);
@@ -398,6 +399,8 @@ static void virtio_balloon_class_init(ObjectClass *klass, void *data)
     vdc->get_config = virtio_balloon_get_config;
     vdc->set_config = virtio_balloon_set_config;
     vdc->get_features = virtio_balloon_get_features;
+    vdc->save = virtio_balloon_save_device;
+    vdc->load = virtio_balloon_load_device;
 }
 
 static const TypeInfo virtio_balloon_info = {

[Qemu-devel] [PATCH RFC 6/8] virtio-rng: implement per-device migration calls

[Greg Kurz]

While we are here, we also check virtio_load() return value.

Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
---
 hw/virtio/virtio-rng.c |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/hw/virtio/virtio-rng.c b/hw/virtio/virtio-rng.c
index 025de81..1356aca 100644
--- a/hw/virtio/virtio-rng.c
+++ b/hw/virtio/virtio-rng.c
@@ -107,19 +107,20 @@ static void virtio_rng_save(QEMUFile *f, void *opaque)
 
 static int virtio_rng_load(QEMUFile *f, void *opaque, int version_id)
 {
-    VirtIORNG *vrng = opaque;
-    VirtIODevice *vdev = VIRTIO_DEVICE(vrng);
-
     if (version_id != 1) {
         return -EINVAL;
     }
-    virtio_load(vdev, f, version_id);
+    return virtio_load(VIRTIO_DEVICE(opaque), f, version_id);
+}
 
+static int virtio_rng_load_device(VirtIODevice *vdev, QEMUFile *f,
+                                  int version_id)
+{
     /* We may have an element ready but couldn't process it due to a quota
      * limit.  Make sure to try again after live migration when the quota may
      * have been reset.
      */
-    virtio_rng_process(vrng);
+    virtio_rng_process(VIRTIO_RNG(vdev));
 
     return 0;
 }
@@ -219,6 +220,7 @@ static void virtio_rng_class_init(ObjectClass *klass, void *data)
     vdc->realize = virtio_rng_device_realize;
     vdc->unrealize = virtio_rng_device_unrealize;
     vdc->get_features = get_features;
+    vdc->load = virtio_rng_load_device;
 }
 
 static void virtio_rng_initfn(Object *obj)

[Qemu-devel] [PATCH RFC 7/8] virtio: add subsections to the migration stream

[Greg Kurz]

There is a need to add some more fields to VirtIODevice that should be
migrated (broken status, endianness). The problem is that we do not
want to break compatibility while adding a new feature... This issue has
been addressed in the generic VMState code with the use of optional
subsections. As a *temporary* alternative to port the whole virtio
migration code to VMState, this patch mimics a similar subsectionning
ability for virtio.

Since each virtio device is streamed in its own section, the idea is to
stream subsections between the end of the device section and the start
of the next sections. This allows an older QEMU to complain and exit
when fed with subsections:

Unknown savevm section type 5
Error -22 while loading VM state

The virtio subsections honor the same protocol than the VMState ones:

 +-------------------------+
 |QEMU_VM_SUBSECTION (byte)| 1 byte
 +-------------------------+
 | subsection name length  | 1 byte
 +-------------------------+
 |                         |
 : subsection name buffer  : length bytes
 |                         |
 +-------------------------+
 |       version_id        | 4 bytes (be32)
 +-------------------------+
 |                         |
 :    subsection data      :
 |                         |
 +-------------------------+

The model differs from VMState though as we don't describe the fields in
the subsections. As a consequence, there is no "field exists" concept and
this impacts backwards migration.

Suggested-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
---
 hw/virtio/virtio.c |   78 +++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 77 insertions(+), 1 deletion(-)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index cf87b44..7fbad29 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -19,6 +19,7 @@
 #include "hw/virtio/virtio.h"
 #include "qemu/atomic.h"
 #include "hw/virtio/virtio-bus.h"
+#include "migration/migration.h"
 
 /*
  * The alignment to use between consumer and producer parts of vring.
@@ -833,6 +834,79 @@ void virtio_notify_config(VirtIODevice *vdev)
     virtio_notify_vector(vdev, vdev->config_vector);
 }
 
+typedef struct VirtIOSubsection {
+    const char *name;
+    int version_id;
+    void (*save)(VirtIODevice *vdev, QEMUFile *f);
+    int (*load)(VirtIODevice *vdev, QEMUFile *f);
+    int (*needed)(VirtIODevice *vdev);
+} VirtIOSubsection;
+
+static const VirtIOSubsection virtio_subsection[] = {
+    { .name = NULL }
+};
+
+static void virtio_save_subsections(VirtIODevice *vdev, QEMUFile *f)
+{
+    int i;
+
+    for (i = 0; virtio_subsection[i].name; i++) {
+        VirtIOSubsection sub = virtio_subsection[i];
+
+        if (sub.needed != NULL && (*sub.needed)(vdev)) {
+            const char *name = sub.name;
+            uint8_t len = strlen(name);
+
+            qemu_put_byte(f, QEMU_VM_SUBSECTION);
+            qemu_put_byte(f, len);
+            qemu_put_buffer(f, (uint8_t *) name, len);
+            qemu_put_be32(f, sub.version_id);
+            (*sub.save)(vdev, f);
+        }
+    }
+}
+
+static int virtio_load_subsections(VirtIODevice *vdev, QEMUFile *f)
+{
+    while (qemu_peek_byte(f, 0) == QEMU_VM_SUBSECTION) {
+        char idstr[256];
+        uint8_t len, size;
+        int i;
+
+        len = qemu_peek_byte(f, 1);
+        size = qemu_peek_buffer(f, (uint8_t *) idstr, len, 2);
+        if (size != len) {
+            break;
+        }
+
+        idstr[size] = 0;
+
+        for (i = 0; virtio_subsection[i].name; i++) {
+            VirtIOSubsection sub = virtio_subsection[i];
+
+            if (strcmp(sub.name, idstr) == 0) {
+                uint32_t version_id;
+                int ret;
+
+                qemu_file_skip(f, 1);   /* subsection */
+                qemu_file_skip(f, 1);   /* len */
+                qemu_file_skip(f, len); /* idstr */
+
+                version_id = qemu_get_be32(f);
+                if (version_id > sub.version_id) {
+                    return -EINVAL;
+                }
+                ret = (*sub.load)(vdev, f);
+                if (ret) {
+                    return ret;
+                }
+            }
+        }
+    }
+
+    return 0;
+}
+
 void virtio_save(VirtIODevice *vdev, QEMUFile *f)
 {
     BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
@@ -876,6 +950,8 @@ void virtio_save(VirtIODevice *vdev, QEMUFile *f)
     if (vdc->save != NULL) {
         vdc->save(vdev, f);
     }
+
+    virtio_save_subsections(vdev, f);
 }
 
 int virtio_set_features(VirtIODevice *vdev, uint32_t val)
@@ -967,7 +1043,7 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f, int version_id)
         return vdc->load(vdev, f, version_id);
     }
 
-    return 0;
+    return virtio_load_subsections(vdev, f);
 }
 
 void virtio_cleanup(VirtIODevice *vdev)

[Qemu-devel] [PATCH RFC 8/8] virtio: add endian-ambivalent support to VirtIODevice

[Greg Kurz]

Some CPU families can dynamically change their endianness. This means we
can have little endian ppc or big endian arm guests for example. This has
an impact on legacy virtio data structures since they are target endian.
We hence introduce a new property to track the endianness of each virtio
device. It is reasonnably assumed that endianness won't change while the
device is in use : we hence capture the device endianness when it gets
reset.

Of course this property must be part of the migration stream as most of
the virtio code will depend on it. It is hence migrated in a subsection
to preserve compatibility with older migration streams. The tricky part
is that the endianness gets known quite late and we must ensure no access
is made to virtio data before that. It is for example invalid to call
vring_avail_idx() as does the actual migration code: the VQ indexes sanity
checks had to be moved from virtio_load() to virtio_load_subsections()
because of that.

We enforce some paranoia by making the endianness a 3-value enum so
that we can temporarily poison it while loading state.

Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
---
 exec.c                     |    8 +---
 hw/virtio/virtio-pci.c     |   11 ++----
 hw/virtio/virtio.c         |   80 +++++++++++++++++++++++++++++++++++++-------
 include/exec/cpu-common.h  |    1 +
 include/hw/virtio/virtio.h |   13 +++++++
 5 files changed, 87 insertions(+), 26 deletions(-)

diff --git a/exec.c b/exec.c
index 91513c6..4e83588 100644
--- a/exec.c
+++ b/exec.c
@@ -2740,13 +2740,7 @@ int cpu_memory_rw_debug(CPUState *cpu, target_ulong addr,
 #endif
 
 #if !defined(CONFIG_USER_ONLY)
-
-/*
- * A helper function for the _utterly broken_ virtio device model to find out if
- * it's running on a big endian machine. Don't do this at home kids!
- */
-bool virtio_is_big_endian(void);
-bool virtio_is_big_endian(void)
+bool target_words_bigendian(void)
 {
 #if defined(TARGET_WORDS_BIGENDIAN)
     return true;
diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index ce97514..2ffceb8 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -89,9 +89,6 @@
 /* Flags track per-device state like workarounds for quirks in older guests. */
 #define VIRTIO_PCI_FLAG_BUS_MASTER_BUG  (1 << 0)
 
-/* HACK for virtio to determine if it's running a big endian guest */
-bool virtio_is_big_endian(void);
-
 static void virtio_pci_bus_new(VirtioBusState *bus, size_t bus_size,
                                VirtIOPCIProxy *dev);
 
@@ -409,13 +406,13 @@ static uint64_t virtio_pci_config_read(void *opaque, hwaddr addr,
         break;
     case 2:
         val = virtio_config_readw(vdev, addr);
-        if (virtio_is_big_endian()) {
+        if (virtio_is_big_endian(vdev)) {
             val = bswap16(val);
         }
         break;
     case 4:
         val = virtio_config_readl(vdev, addr);
-        if (virtio_is_big_endian()) {
+        if (virtio_is_big_endian(vdev)) {
             val = bswap32(val);
         }
         break;
@@ -443,13 +440,13 @@ static void virtio_pci_config_write(void *opaque, hwaddr addr,
         virtio_config_writeb(vdev, addr, val);
         break;
     case 2:
-        if (virtio_is_big_endian()) {
+        if (virtio_is_big_endian(vdev)) {
             val = bswap16(val);
         }
         virtio_config_writew(vdev, addr, val);
         break;
     case 4:
-        if (virtio_is_big_endian()) {
+        if (virtio_is_big_endian(vdev)) {
             val = bswap32(val);
         }
         virtio_config_writel(vdev, addr, val);
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 7fbad29..6578854 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -539,6 +539,15 @@ void virtio_set_status(VirtIODevice *vdev, uint8_t val)
     vdev->status = val;
 }
 
+static void virtio_set_endian_target_default(VirtIODevice *vdev)
+{
+    if (target_words_bigendian()) {
+        vdev->device_endian = VIRTIO_DEVICE_ENDIAN_BIG;
+    } else {
+        vdev->device_endian = VIRTIO_DEVICE_ENDIAN_LITTLE;
+    }
+}
+
 void virtio_reset(void *opaque)
 {
     VirtIODevice *vdev = opaque;
@@ -546,6 +555,7 @@ void virtio_reset(void *opaque)
     int i;
 
     virtio_set_status(vdev, 0);
+    virtio_set_endian_target_default(vdev);
 
     if (k->reset) {
         k->reset(vdev);
@@ -839,10 +849,39 @@ typedef struct VirtIOSubsection {
     int version_id;
     void (*save)(VirtIODevice *vdev, QEMUFile *f);
     int (*load)(VirtIODevice *vdev, QEMUFile *f);
-    int (*needed)(VirtIODevice *vdev);
+    bool (*needed)(VirtIODevice *vdev);
 } VirtIOSubsection;
 
+static void virtio_save_device_endian(VirtIODevice *vdev, QEMUFile *f)
+{
+    qemu_put_byte(f, vdev->device_endian);
+}
+
+static int virtio_load_device_endian(VirtIODevice *vdev, QEMUFile *f)
+{
+    vdev->device_endian = qemu_get_byte(f);
+    return 0;
+}
+
+static bool virtio_device_endian_needed(VirtIODevice *vdev)
+{
+    /* No migration is supposed to occur while we are loading state.
+     */
+    assert(vdev->device_endian != VIRTIO_DEVICE_ENDIAN_UNKNOWN);
+    if (target_words_bigendian()) {
+        return vdev->device_endian == VIRTIO_DEVICE_ENDIAN_LITTLE;
+    } else {
+        return vdev->device_endian == VIRTIO_DEVICE_ENDIAN_BIG;
+    }
+}
+
 static const VirtIOSubsection virtio_subsection[] = {
+    { .name = "virtio/device_endian",
+      .version_id = 1,
+      .save = virtio_save_device_endian,
+      .load = virtio_load_device_endian,
+      .needed = virtio_device_endian_needed,
+    },
     { .name = NULL }
 };
 
@@ -868,6 +907,8 @@ static void virtio_save_subsections(VirtIODevice *vdev, QEMUFile *f)
 
 static int virtio_load_subsections(VirtIODevice *vdev, QEMUFile *f)
 {
+    int i;
+
     while (qemu_peek_byte(f, 0) == QEMU_VM_SUBSECTION) {
         char idstr[256];
         uint8_t len, size;
@@ -904,6 +945,26 @@ static int virtio_load_subsections(VirtIODevice *vdev, QEMUFile *f)
         }
     }
 
+    for (i = 0; i < VIRTIO_PCI_QUEUE_MAX; i++) {
+        if (vdev->vq[i].vring.num == 0) {
+            break;
+        }
+
+        if (vdev->vq[i].pa) {
+            uint16_t nheads;
+            nheads = vring_avail_idx(&vdev->vq[i]) - vdev->vq[i].last_avail_idx;
+            /* Check it isn't doing strange things with descriptor numbers. */
+            if (nheads > vdev->vq[i].vring.num) {
+                error_report("VQ %d size 0x%x Guest index 0x%x "
+                             "inconsistent with Host index 0x%x: delta 0x%x",
+                             i, vdev->vq[i].vring.num,
+                             vring_avail_idx(&vdev->vq[i]),
+                             vdev->vq[i].last_avail_idx, nheads);
+                return -1;
+            }
+        }
+    }
+
     return 0;
 }
 
@@ -979,6 +1040,11 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f, int version_id)
     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
     VirtioDeviceClass *vdc = VIRTIO_DEVICE_GET_CLASS(vdev);
 
+    /* We poison the endianness to ensure it does not get used before
+     * subsections have been loaded.
+     */
+    vdev->device_endian = VIRTIO_DEVICE_ENDIAN_UNKNOWN;
+
     if (k->load_config) {
         ret = k->load_config(qbus->parent, f);
         if (ret)
@@ -1012,18 +1078,7 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f, int version_id)
         vdev->vq[i].notification = true;
 
         if (vdev->vq[i].pa) {
-            uint16_t nheads;
             virtqueue_init(&vdev->vq[i]);
-            nheads = vring_avail_idx(&vdev->vq[i]) - vdev->vq[i].last_avail_idx;
-            /* Check it isn't doing very strange things with descriptor numbers. */
-            if (nheads > vdev->vq[i].vring.num) {
-                error_report("VQ %d size 0x%x Guest index 0x%x "
-                             "inconsistent with Host index 0x%x: delta 0x%x",
-                             i, vdev->vq[i].vring.num,
-                             vring_avail_idx(&vdev->vq[i]),
-                             vdev->vq[i].last_avail_idx, nheads);
-                return -1;
-            }
         } else if (vdev->vq[i].last_avail_idx) {
             error_report("VQ %d address 0x0 "
                          "inconsistent with Host index 0x%x",
@@ -1100,6 +1155,7 @@ void virtio_init(VirtIODevice *vdev, const char *name,
     }
     vdev->vmstate = qemu_add_vm_change_state_handler(virtio_vmstate_change,
                                                      vdev);
+    virtio_set_endian_target_default(vdev);
 }
 
 hwaddr virtio_queue_get_desc_addr(VirtIODevice *vdev, int n)
diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
index a21b65a..eb798c1 100644
--- a/include/exec/cpu-common.h
+++ b/include/exec/cpu-common.h
@@ -122,4 +122,5 @@ void qemu_ram_foreach_block(RAMBlockIterFunc func, void *opaque);
 
 #endif
 
+bool target_words_bigendian(void);
 #endif /* !CPU_COMMON_H */
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index 3505ce5..1c4a736 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -104,6 +104,12 @@ typedef struct VirtQueueElement
 #define VIRTIO_DEVICE(obj) \
         OBJECT_CHECK(VirtIODevice, (obj), TYPE_VIRTIO_DEVICE)
 
+enum virtio_device_endian {
+    VIRTIO_DEVICE_ENDIAN_UNKNOWN,
+    VIRTIO_DEVICE_ENDIAN_LITTLE,
+    VIRTIO_DEVICE_ENDIAN_BIG,
+};
+
 struct VirtIODevice
 {
     DeviceState parent_obj;
@@ -121,6 +127,7 @@ struct VirtIODevice
     bool vm_running;
     VMChangeStateEntry *vmstate;
     char *bus_name;
+    enum virtio_device_endian device_endian;
 };
 
 typedef struct VirtioDeviceClass {
@@ -255,4 +262,10 @@ void virtio_queue_set_host_notifier_fd_handler(VirtQueue *vq, bool assign,
                                                bool set_handler);
 void virtio_queue_notify_vq(VirtQueue *vq);
 void virtio_irq(VirtQueue *vq);
+
+static inline bool virtio_is_big_endian(VirtIODevice *vdev)
+{
+    assert(vdev->device_endian != VIRTIO_DEVICE_ENDIAN_UNKNOWN);
+    return vdev->device_endian == VIRTIO_DEVICE_ENDIAN_BIG;
+}
 #endif

Re: [Qemu-devel] [PATCH RFC 8/8] virtio: add endian-ambivalent support to VirtIODevice

[Greg Kurz]

On Mon, 19 May 2014 10:39:09 +0200
Greg Kurz <gkurz@linux.vnet.ibm.com> wrote:

> Some CPU families can dynamically change their endianness. This means we
> can have little endian ppc or big endian arm guests for example. This has
> an impact on legacy virtio data structures since they are target endian.
> We hence introduce a new property to track the endianness of each virtio
> device. It is reasonnably assumed that endianness won't change while the
> device is in use : we hence capture the device endianness when it gets
> reset.
> 
> Of course this property must be part of the migration stream as most of
> the virtio code will depend on it. It is hence migrated in a subsection
> to preserve compatibility with older migration streams. The tricky part
> is that the endianness gets known quite late and we must ensure no access
> is made to virtio data before that. It is for example invalid to call
> vring_avail_idx() as does the actual migration code: the VQ indexes sanity
> checks had to be moved from virtio_load() to virtio_load_subsections()
> because of that.
> 
> We enforce some paranoia by making the endianness a 3-value enum so
> that we can temporarily poison it while loading state.
> 
> Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
> ---
>  exec.c                     |    8 +---
>  hw/virtio/virtio-pci.c     |   11 ++----
>  hw/virtio/virtio.c         |   80 +++++++++++++++++++++++++++++++++++++-------
>  include/exec/cpu-common.h  |    1 +
>  include/hw/virtio/virtio.h |   13 +++++++
>  5 files changed, 87 insertions(+), 26 deletions(-)
> 
> diff --git a/exec.c b/exec.c
> index 91513c6..4e83588 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -2740,13 +2740,7 @@ int cpu_memory_rw_debug(CPUState *cpu, target_ulong addr,
>  #endif
> 
>  #if !defined(CONFIG_USER_ONLY)
> -
> -/*
> - * A helper function for the _utterly broken_ virtio device model to find out if
> - * it's running on a big endian machine. Don't do this at home kids!
> - */
> -bool virtio_is_big_endian(void);
> -bool virtio_is_big_endian(void)
> +bool target_words_bigendian(void)
>  {
>  #if defined(TARGET_WORDS_BIGENDIAN)
>      return true;
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index ce97514..2ffceb8 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -89,9 +89,6 @@
>  /* Flags track per-device state like workarounds for quirks in older guests. */
>  #define VIRTIO_PCI_FLAG_BUS_MASTER_BUG  (1 << 0)
> 
> -/* HACK for virtio to determine if it's running a big endian guest */
> -bool virtio_is_big_endian(void);
> -
>  static void virtio_pci_bus_new(VirtioBusState *bus, size_t bus_size,
>                                 VirtIOPCIProxy *dev);
> 
> @@ -409,13 +406,13 @@ static uint64_t virtio_pci_config_read(void *opaque, hwaddr addr,
>          break;
>      case 2:
>          val = virtio_config_readw(vdev, addr);
> -        if (virtio_is_big_endian()) {
> +        if (virtio_is_big_endian(vdev)) {
>              val = bswap16(val);
>          }
>          break;
>      case 4:
>          val = virtio_config_readl(vdev, addr);
> -        if (virtio_is_big_endian()) {
> +        if (virtio_is_big_endian(vdev)) {
>              val = bswap32(val);
>          }
>          break;
> @@ -443,13 +440,13 @@ static void virtio_pci_config_write(void *opaque, hwaddr addr,
>          virtio_config_writeb(vdev, addr, val);
>          break;
>      case 2:
> -        if (virtio_is_big_endian()) {
> +        if (virtio_is_big_endian(vdev)) {
>              val = bswap16(val);
>          }
>          virtio_config_writew(vdev, addr, val);
>          break;
>      case 4:
> -        if (virtio_is_big_endian()) {
> +        if (virtio_is_big_endian(vdev)) {
>              val = bswap32(val);
>          }
>          virtio_config_writel(vdev, addr, val);
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 7fbad29..6578854 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -539,6 +539,15 @@ void virtio_set_status(VirtIODevice *vdev, uint8_t val)
>      vdev->status = val;
>  }
> 
> +static void virtio_set_endian_target_default(VirtIODevice *vdev)
> +{
> +    if (target_words_bigendian()) {
> +        vdev->device_endian = VIRTIO_DEVICE_ENDIAN_BIG;
> +    } else {
> +        vdev->device_endian = VIRTIO_DEVICE_ENDIAN_LITTLE;
> +    }
> +}
> +
>  void virtio_reset(void *opaque)
>  {
>      VirtIODevice *vdev = opaque;
> @@ -546,6 +555,7 @@ void virtio_reset(void *opaque)
>      int i;
> 
>      virtio_set_status(vdev, 0);
> +    virtio_set_endian_target_default(vdev);
> 
>      if (k->reset) {
>          k->reset(vdev);
> @@ -839,10 +849,39 @@ typedef struct VirtIOSubsection {
>      int version_id;
>      void (*save)(VirtIODevice *vdev, QEMUFile *f);
>      int (*load)(VirtIODevice *vdev, QEMUFile *f);
> -    int (*needed)(VirtIODevice *vdev);
> +    bool (*needed)(VirtIODevice *vdev);
>  } VirtIOSubsection;
> 
> +static void virtio_save_device_endian(VirtIODevice *vdev, QEMUFile *f)
> +{
> +    qemu_put_byte(f, vdev->device_endian);
> +}
> +
> +static int virtio_load_device_endian(VirtIODevice *vdev, QEMUFile *f)
> +{
> +    vdev->device_endian = qemu_get_byte(f);
> +    return 0;
> +}
> +
> +static bool virtio_device_endian_needed(VirtIODevice *vdev)
> +{
> +    /* No migration is supposed to occur while we are loading state.
> +     */
> +    assert(vdev->device_endian != VIRTIO_DEVICE_ENDIAN_UNKNOWN);
> +    if (target_words_bigendian()) {
> +        return vdev->device_endian == VIRTIO_DEVICE_ENDIAN_LITTLE;
> +    } else {
> +        return vdev->device_endian == VIRTIO_DEVICE_ENDIAN_BIG;
> +    }
> +}
> +
>  static const VirtIOSubsection virtio_subsection[] = {
> +    { .name = "virtio/device_endian",

Can anyone comment the subsection name ? Is there a chance the
VMState port would come up with the same ?

> +      .version_id = 1,
> +      .save = virtio_save_device_endian,
> +      .load = virtio_load_device_endian,
> +      .needed = virtio_device_endian_needed,
> +    },
>      { .name = NULL }
>  };
> 
> @@ -868,6 +907,8 @@ static void virtio_save_subsections(VirtIODevice *vdev, QEMUFile *f)
> 
>  static int virtio_load_subsections(VirtIODevice *vdev, QEMUFile *f)
>  {
> +    int i;
> +
>      while (qemu_peek_byte(f, 0) == QEMU_VM_SUBSECTION) {
>          char idstr[256];
>          uint8_t len, size;
> @@ -904,6 +945,26 @@ static int virtio_load_subsections(VirtIODevice *vdev, QEMUFile *f)
>          }
>      }
> 
> +    for (i = 0; i < VIRTIO_PCI_QUEUE_MAX; i++) {
> +        if (vdev->vq[i].vring.num == 0) {
> +            break;
> +        }
> +
> +        if (vdev->vq[i].pa) {
> +            uint16_t nheads;
> +            nheads = vring_avail_idx(&vdev->vq[i]) - vdev->vq[i].last_avail_idx;
> +            /* Check it isn't doing strange things with descriptor numbers. */
> +            if (nheads > vdev->vq[i].vring.num) {
> +                error_report("VQ %d size 0x%x Guest index 0x%x "
> +                             "inconsistent with Host index 0x%x: delta 0x%x",
> +                             i, vdev->vq[i].vring.num,
> +                             vring_avail_idx(&vdev->vq[i]),
> +                             vdev->vq[i].last_avail_idx, nheads);
> +                return -1;
> +            }
> +        }
> +    }
> +
>      return 0;
>  }
> 
> @@ -979,6 +1040,11 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f, int version_id)
>      VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
>      VirtioDeviceClass *vdc = VIRTIO_DEVICE_GET_CLASS(vdev);
> 
> +    /* We poison the endianness to ensure it does not get used before
> +     * subsections have been loaded.
> +     */
> +    vdev->device_endian = VIRTIO_DEVICE_ENDIAN_UNKNOWN;
> +
>      if (k->load_config) {
>          ret = k->load_config(qbus->parent, f);
>          if (ret)
> @@ -1012,18 +1078,7 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f, int version_id)
>          vdev->vq[i].notification = true;
> 
>          if (vdev->vq[i].pa) {
> -            uint16_t nheads;
>              virtqueue_init(&vdev->vq[i]);
> -            nheads = vring_avail_idx(&vdev->vq[i]) - vdev->vq[i].last_avail_idx;
> -            /* Check it isn't doing very strange things with descriptor numbers. */
> -            if (nheads > vdev->vq[i].vring.num) {
> -                error_report("VQ %d size 0x%x Guest index 0x%x "
> -                             "inconsistent with Host index 0x%x: delta 0x%x",
> -                             i, vdev->vq[i].vring.num,
> -                             vring_avail_idx(&vdev->vq[i]),
> -                             vdev->vq[i].last_avail_idx, nheads);
> -                return -1;
> -            }
>          } else if (vdev->vq[i].last_avail_idx) {
>              error_report("VQ %d address 0x0 "
>                           "inconsistent with Host index 0x%x",
> @@ -1100,6 +1155,7 @@ void virtio_init(VirtIODevice *vdev, const char *name,
>      }
>      vdev->vmstate = qemu_add_vm_change_state_handler(virtio_vmstate_change,
>                                                       vdev);
> +    virtio_set_endian_target_default(vdev);
>  }
> 
>  hwaddr virtio_queue_get_desc_addr(VirtIODevice *vdev, int n)
> diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
> index a21b65a..eb798c1 100644
> --- a/include/exec/cpu-common.h
> +++ b/include/exec/cpu-common.h
> @@ -122,4 +122,5 @@ void qemu_ram_foreach_block(RAMBlockIterFunc func, void *opaque);
> 
>  #endif
> 
> +bool target_words_bigendian(void);
>  #endif /* !CPU_COMMON_H */
> diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> index 3505ce5..1c4a736 100644
> --- a/include/hw/virtio/virtio.h
> +++ b/include/hw/virtio/virtio.h
> @@ -104,6 +104,12 @@ typedef struct VirtQueueElement
>  #define VIRTIO_DEVICE(obj) \
>          OBJECT_CHECK(VirtIODevice, (obj), TYPE_VIRTIO_DEVICE)
> 
> +enum virtio_device_endian {
> +    VIRTIO_DEVICE_ENDIAN_UNKNOWN,
> +    VIRTIO_DEVICE_ENDIAN_LITTLE,
> +    VIRTIO_DEVICE_ENDIAN_BIG,
> +};
> +
>  struct VirtIODevice
>  {
>      DeviceState parent_obj;
> @@ -121,6 +127,7 @@ struct VirtIODevice
>      bool vm_running;
>      VMChangeStateEntry *vmstate;
>      char *bus_name;
> +    enum virtio_device_endian device_endian;
>  };
> 
>  typedef struct VirtioDeviceClass {
> @@ -255,4 +262,10 @@ void virtio_queue_set_host_notifier_fd_handler(VirtQueue *vq, bool assign,
>                                                 bool set_handler);
>  void virtio_queue_notify_vq(VirtQueue *vq);
>  void virtio_irq(VirtQueue *vq);
> +
> +static inline bool virtio_is_big_endian(VirtIODevice *vdev)
> +{
> +    assert(vdev->device_endian != VIRTIO_DEVICE_ENDIAN_UNKNOWN);
> +    return vdev->device_endian == VIRTIO_DEVICE_ENDIAN_BIG;
> +}
>  #endif
> 
> 



-- 
Gregory Kurz                                     kurzgreg@fr.ibm.com
                                                 gkurz@linux.vnet.ibm.com
Software Engineer @ IBM/Meiosys                  http://www.ibm.com
Tel +33 (0)562 165 496

"Anarchy is about taking complete responsibility for yourself."
        Alan Moore.

Re: [Qemu-devel] [PATCH RFC 8/8] virtio: add endian-ambivalent support to VirtIODevice

[Andreas Färber]

Am 19.05.2014 15:06, schrieb Greg Kurz:
> On Mon, 19 May 2014 10:39:09 +0200
> Greg Kurz <gkurz@linux.vnet.ibm.com> wrote:
>> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
>> index 7fbad29..6578854 100644
>> --- a/hw/virtio/virtio.c
>> +++ b/hw/virtio/virtio.c
[...]
>> @@ -839,10 +849,39 @@ typedef struct VirtIOSubsection {
>>      int version_id;
>>      void (*save)(VirtIODevice *vdev, QEMUFile *f);
>>      int (*load)(VirtIODevice *vdev, QEMUFile *f);
>> -    int (*needed)(VirtIODevice *vdev);
>> +    bool (*needed)(VirtIODevice *vdev);
>>  } VirtIOSubsection;
>>
>> +static void virtio_save_device_endian(VirtIODevice *vdev, QEMUFile *f)
>> +{
>> +    qemu_put_byte(f, vdev->device_endian);
>> +}
>> +
>> +static int virtio_load_device_endian(VirtIODevice *vdev, QEMUFile *f)
>> +{
>> +    vdev->device_endian = qemu_get_byte(f);
>> +    return 0;
>> +}
>> +
>> +static bool virtio_device_endian_needed(VirtIODevice *vdev)
>> +{
>> +    /* No migration is supposed to occur while we are loading state.
>> +     */
>> +    assert(vdev->device_endian != VIRTIO_DEVICE_ENDIAN_UNKNOWN);
>> +    if (target_words_bigendian()) {
>> +        return vdev->device_endian == VIRTIO_DEVICE_ENDIAN_LITTLE;
>> +    } else {
>> +        return vdev->device_endian == VIRTIO_DEVICE_ENDIAN_BIG;
>> +    }
>> +}
>> +
>>  static const VirtIOSubsection virtio_subsection[] = {
>> +    { .name = "virtio/device_endian",
> 
> Can anyone comment the subsection name ? Is there a chance the
> VMState port would come up with the same ?
> 
>> +      .version_id = 1,
>> +      .save = virtio_save_device_endian,
>> +      .load = virtio_load_device_endian,
>> +      .needed = virtio_device_endian_needed,
>> +    },
>>      { .name = NULL }
>>  };
>>

Different question: With converting VirtIO to VMState in mind, why are
you not using a regular VMStateSubsection and loading/saving that as
part of the old-style load/save functions? Is an API for that missing?

Regards,
Andreas

-- 
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany
GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg

Re: [Qemu-devel] [PATCH RFC 8/8] virtio: add endian-ambivalent support to VirtIODevice

[Greg Kurz]

On Mon, 19 May 2014 19:06:39 +0200
Andreas Färber <afaerber@suse.de> wrote:

> Am 19.05.2014 15:06, schrieb Greg Kurz:
> > On Mon, 19 May 2014 10:39:09 +0200
> > Greg Kurz <gkurz@linux.vnet.ibm.com> wrote:
> >> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> >> index 7fbad29..6578854 100644
> >> --- a/hw/virtio/virtio.c
> >> +++ b/hw/virtio/virtio.c
> [...]
> >> @@ -839,10 +849,39 @@ typedef struct VirtIOSubsection {
> >>      int version_id;
> >>      void (*save)(VirtIODevice *vdev, QEMUFile *f);
> >>      int (*load)(VirtIODevice *vdev, QEMUFile *f);
> >> -    int (*needed)(VirtIODevice *vdev);
> >> +    bool (*needed)(VirtIODevice *vdev);
> >>  } VirtIOSubsection;
> >>
> >> +static void virtio_save_device_endian(VirtIODevice *vdev, QEMUFile *f)
> >> +{
> >> +    qemu_put_byte(f, vdev->device_endian);
> >> +}
> >> +
> >> +static int virtio_load_device_endian(VirtIODevice *vdev, QEMUFile *f)
> >> +{
> >> +    vdev->device_endian = qemu_get_byte(f);
> >> +    return 0;
> >> +}
> >> +
> >> +static bool virtio_device_endian_needed(VirtIODevice *vdev)
> >> +{
> >> +    /* No migration is supposed to occur while we are loading state.
> >> +     */
> >> +    assert(vdev->device_endian != VIRTIO_DEVICE_ENDIAN_UNKNOWN);
> >> +    if (target_words_bigendian()) {
> >> +        return vdev->device_endian == VIRTIO_DEVICE_ENDIAN_LITTLE;
> >> +    } else {
> >> +        return vdev->device_endian == VIRTIO_DEVICE_ENDIAN_BIG;
> >> +    }
> >> +}
> >> +
> >>  static const VirtIOSubsection virtio_subsection[] = {
> >> +    { .name = "virtio/device_endian",
> > 
> > Can anyone comment the subsection name ? Is there a chance the
> > VMState port would come up with the same ?
> > 
> >> +      .version_id = 1,
> >> +      .save = virtio_save_device_endian,
> >> +      .load = virtio_load_device_endian,
> >> +      .needed = virtio_device_endian_needed,
> >> +    },
> >>      { .name = NULL }
> >>  };
> >>
> 
> Different question: With converting VirtIO to VMState in mind, why are
> you not using a regular VMStateSubsection and loading/saving that as
> part of the old-style load/save functions? Is an API for that missing?
> 

I guess because I haven't tried yet. :)
I'll have a closer look at this.

> Regards,
> Andreas
> 

Thanks.

-- 
Gregory Kurz                                     kurzgreg@fr.ibm.com
                                                 gkurz@linux.vnet.ibm.com
Software Engineer @ IBM/Meiosys                  http://www.ibm.com
Tel +33 (0)562 165 496

"Anarchy is about taking complete responsibility for yourself."
        Alan Moore.

Re: [Qemu-devel] [PATCH RFC 8/8] virtio: add endian-ambivalent support to VirtIODevice

[Dr. David Alan Gilbert]

* Andreas F?rber (afaerber@suse.de) wrote:
> Am 19.05.2014 15:06, schrieb Greg Kurz:
> > On Mon, 19 May 2014 10:39:09 +0200
> > Greg Kurz <gkurz@linux.vnet.ibm.com> wrote:
> >> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> >> index 7fbad29..6578854 100644
> >> --- a/hw/virtio/virtio.c
> >> +++ b/hw/virtio/virtio.c
> [...]
> >> @@ -839,10 +849,39 @@ typedef struct VirtIOSubsection {
> >>      int version_id;
> >>      void (*save)(VirtIODevice *vdev, QEMUFile *f);
> >>      int (*load)(VirtIODevice *vdev, QEMUFile *f);
> >> -    int (*needed)(VirtIODevice *vdev);
> >> +    bool (*needed)(VirtIODevice *vdev);
> >>  } VirtIOSubsection;
> >>
> >> +static void virtio_save_device_endian(VirtIODevice *vdev, QEMUFile *f)
> >> +{
> >> +    qemu_put_byte(f, vdev->device_endian);
> >> +}
> >> +
> >> +static int virtio_load_device_endian(VirtIODevice *vdev, QEMUFile *f)
> >> +{
> >> +    vdev->device_endian = qemu_get_byte(f);
> >> +    return 0;
> >> +}
> >> +
> >> +static bool virtio_device_endian_needed(VirtIODevice *vdev)
> >> +{
> >> +    /* No migration is supposed to occur while we are loading state.
> >> +     */
> >> +    assert(vdev->device_endian != VIRTIO_DEVICE_ENDIAN_UNKNOWN);
> >> +    if (target_words_bigendian()) {
> >> +        return vdev->device_endian == VIRTIO_DEVICE_ENDIAN_LITTLE;
> >> +    } else {
> >> +        return vdev->device_endian == VIRTIO_DEVICE_ENDIAN_BIG;
> >> +    }
> >> +}
> >> +
> >>  static const VirtIOSubsection virtio_subsection[] = {
> >> +    { .name = "virtio/device_endian",
> > 
> > Can anyone comment the subsection name ? Is there a chance the
> > VMState port would come up with the same ?
> > 
> >> +      .version_id = 1,
> >> +      .save = virtio_save_device_endian,
> >> +      .load = virtio_load_device_endian,
> >> +      .needed = virtio_device_endian_needed,
> >> +    },
> >>      { .name = NULL }
> >>  };
> >>
> 
> Different question: With converting VirtIO to VMState in mind, why are
> you not using a regular VMStateSubsection and loading/saving that as
> part of the old-style load/save functions? Is an API for that missing?

There are a handful of places that call into vmstate from a non-vmstate
routine but I don't think they're using plain subsections.

hw/pci/pci.c: pci_device_save/load
hw/scsi/spapr_vscsi.c: vscsi_save_request
hw/acpi/piix4.c: acpi_load_old

Dave
> 
> Regards,
> Andreas
> 
> -- 
> SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany
> GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

Re: [Qemu-devel] [PATCH RFC V2 0/8] virtio: migrate new properties

[Alexander Graf]

On 19.05.14 10:38, Greg Kurz wrote:
> Hi,
>
> This patch set tries to address comments from the initial
> review. For this round, I have focused on two changes:
> - as suggested by Andreas, we now call the device specific
>    code from the generic code to ease the implementation of
>    future devices. This is achieved with the addition of
>    load/save methods to VirtioDeviceClass.
> - virtio subsections now implement a "needed" concept with
>    the same semantics as in the VMState code.
>
> I haven't looked at compat mode issues yet, but it is
> on my TODO list.

If you fix up the comments to be either

   /*
    * foo
    */

or

   /* foo */

style, not

   /* foo
    */

then you get my


Acked-by: Alexander Graf <agraf@suse.de>


Alex

Re: [Qemu-devel] [PATCH RFC V2 0/8] virtio: migrate new properties

[Greg Kurz]

On Mon, 19 May 2014 14:02:39 +0200
Alexander Graf <agraf@suse.de> wrote:

> 
> On 19.05.14 10:38, Greg Kurz wrote:
> > Hi,
> >
> > This patch set tries to address comments from the initial
> > review. For this round, I have focused on two changes:
> > - as suggested by Andreas, we now call the device specific
> >    code from the generic code to ease the implementation of
> >    future devices. This is achieved with the addition of
> >    load/save methods to VirtioDeviceClass.
> > - virtio subsections now implement a "needed" concept with
> >    the same semantics as in the VMState code.
> >
> > I haven't looked at compat mode issues yet, but it is
> > on my TODO list.
> 
> If you fix up the comments to be either
> 
>    /*
>     * foo
>     */
> 
> or
> 
>    /* foo */
> 
> style, not
> 
>    /* foo
>     */
> 
> then you get my
> 
> 
> Acked-by: Alexander Graf <agraf@suse.de>
> 
> 
> Alex
> 

I'll certainly do that then ! :)

BTW, the faulty comments are in patch 8/8 that I was
sending for informational purpose only as it is part
of the bi-endian virtio serie. Should I merge the
two patch sets at some point ?

-- 
Gregory Kurz                                     kurzgreg@fr.ibm.com
                                                 gkurz@linux.vnet.ibm.com
Software Engineer @ IBM/Meiosys                  http://www.ibm.com
Tel +33 (0)562 165 496

"Anarchy is about taking complete responsibility for yourself."
        Alan Moore.

Re: [Qemu-devel] [PATCH RFC V2 0/8] virtio: migrate new properties

[Alexander Graf]

On 19.05.14 14:45, Greg Kurz wrote:
> On Mon, 19 May 2014 14:02:39 +0200
> Alexander Graf <agraf@suse.de> wrote:
>
>> On 19.05.14 10:38, Greg Kurz wrote:
>>> Hi,
>>>
>>> This patch set tries to address comments from the initial
>>> review. For this round, I have focused on two changes:
>>> - as suggested by Andreas, we now call the device specific
>>>     code from the generic code to ease the implementation of
>>>     future devices. This is achieved with the addition of
>>>     load/save methods to VirtioDeviceClass.
>>> - virtio subsections now implement a "needed" concept with
>>>     the same semantics as in the VMState code.
>>>
>>> I haven't looked at compat mode issues yet, but it is
>>> on my TODO list.
>> If you fix up the comments to be either
>>
>>     /*
>>      * foo
>>      */
>>
>> or
>>
>>     /* foo */
>>
>> style, not
>>
>>     /* foo
>>      */
>>
>> then you get my
>>
>>
>> Acked-by: Alexander Graf <agraf@suse.de>
>>
>>
>> Alex
>>
> I'll certainly do that then ! :)
>
> BTW, the faulty comments are in patch 8/8 that I was
> sending for informational purpose only as it is part
> of the bi-endian virtio serie. Should I merge the
> two patch sets at some point ?


Either way works for me, let's wait for virtio and migration specialists 
to comment first ;)


Alex

Re: [Qemu-devel] [PATCH RFC V2 0/8] virtio: migrate new properties

[Michael S. Tsirkin]

On Mon, May 19, 2014 at 02:02:39PM +0200, Alexander Graf wrote:
> 
> On 19.05.14 10:38, Greg Kurz wrote:
> >Hi,
> >
> >This patch set tries to address comments from the initial
> >review. For this round, I have focused on two changes:
> >- as suggested by Andreas, we now call the device specific
> >   code from the generic code to ease the implementation of
> >   future devices. This is achieved with the addition of
> >   load/save methods to VirtioDeviceClass.
> >- virtio subsections now implement a "needed" concept with
> >   the same semantics as in the VMState code.
> >
> >I haven't looked at compat mode issues yet, but it is
> >on my TODO list.
> 
> If you fix up the comments to be either
> 
>   /*
>    * foo
>    */
> 
> or
> 
>   /* foo */
> 
> style, not
> 
>   /* foo
>    */
> 
> then you get my
> 
> 
> Acked-by: Alexander Graf <agraf@suse.de>
> 
> 
> Alex

Documented anywhere?
Linux style is

        /* Always
         * like this.
         */

so it's definitely not universal.


-- 
MST

Re: [Qemu-devel] [PATCH RFC V2 0/8] virtio: migrate new properties

[Alexander Graf]

On 19.05.14 17:10, Michael S. Tsirkin wrote:
> On Mon, May 19, 2014 at 02:02:39PM +0200, Alexander Graf wrote:
>> On 19.05.14 10:38, Greg Kurz wrote:
>>> Hi,
>>>
>>> This patch set tries to address comments from the initial
>>> review. For this round, I have focused on two changes:
>>> - as suggested by Andreas, we now call the device specific
>>>    code from the generic code to ease the implementation of
>>>    future devices. This is achieved with the addition of
>>>    load/save methods to VirtioDeviceClass.
>>> - virtio subsections now implement a "needed" concept with
>>>    the same semantics as in the VMState code.
>>>
>>> I haven't looked at compat mode issues yet, but it is
>>> on my TODO list.
>> If you fix up the comments to be either
>>
>>    /*
>>     * foo
>>     */
>>
>> or
>>
>>    /* foo */
>>
>> style, not
>>
>>    /* foo
>>     */
>>
>> then you get my
>>
>>
>> Acked-by: Alexander Graf <agraf@suse.de>
>>
>>
>> Alex
> Documented anywhere?

Impressive. I thought it was, but apparently I'm wrong :). Nevermind then.

> Linux style is
>
>          /* Always
>           * like this.
>           */
>
> so it's definitely not universal.

Eh - documented anywhere? Linux usually goes with C style comments.


Alex

Re: [Qemu-devel] [PATCH RFC V2 0/8] virtio: migrate new properties

[Michael S. Tsirkin]

On Mon, May 19, 2014 at 05:36:38PM +0200, Alexander Graf wrote:
> 
> On 19.05.14 17:10, Michael S. Tsirkin wrote:
> >On Mon, May 19, 2014 at 02:02:39PM +0200, Alexander Graf wrote:
> >>On 19.05.14 10:38, Greg Kurz wrote:
> >>>Hi,
> >>>
> >>>This patch set tries to address comments from the initial
> >>>review. For this round, I have focused on two changes:
> >>>- as suggested by Andreas, we now call the device specific
> >>>   code from the generic code to ease the implementation of
> >>>   future devices. This is achieved with the addition of
> >>>   load/save methods to VirtioDeviceClass.
> >>>- virtio subsections now implement a "needed" concept with
> >>>   the same semantics as in the VMState code.
> >>>
> >>>I haven't looked at compat mode issues yet, but it is
> >>>on my TODO list.
> >>If you fix up the comments to be either
> >>
> >>   /*
> >>    * foo
> >>    */
> >>
> >>or
> >>
> >>   /* foo */
> >>
> >>style, not
> >>
> >>   /* foo
> >>    */
> >>
> >>then you get my
> >>
> >>
> >>Acked-by: Alexander Graf <agraf@suse.de>
> >>
> >>
> >>Alex
> >Documented anywhere?
> 
> Impressive. I thought it was, but apparently I'm wrong :). Nevermind then.
> 
> >Linux style is
> >
> >         /* Always
> >          * like this.
> >          */
> >
> >so it's definitely not universal.
> 
> Eh - documented anywhere? Linux usually goes with C style comments.
> 
> 
> Alex

Actually, what I said is only true for networking, I'm
just hacking in that field recently.
It's all in Documentation/CodingStyle:


The preferred style for long (multi-line) comments is:

        /*
         * This is the preferred style for multi-line
         * comments in the Linux kernel source code.
         * Please use it consistently.
         *
         * Description:  A column of asterisks on the left side,
         * with beginning and ending almost-blank lines.
         */

For files in net/ and drivers/net/ the preferred style for long (multi-line)
comments is a little different.

        /* The preferred comment style for files in net/ and drivers/net
         * looks like this.
         *
         * It is nearly the same as the generally preferred comment style,
         * but there is no initial almost-blank line.
         */

Re: [Qemu-devel] [PATCH RFC V2 0/8] virtio: migrate new properties

[Andreas Färber]

Am 19.05.2014 17:10, schrieb Michael S. Tsirkin:
> On Mon, May 19, 2014 at 02:02:39PM +0200, Alexander Graf wrote:
>>
>> On 19.05.14 10:38, Greg Kurz wrote:
>>> Hi,
>>>
>>> This patch set tries to address comments from the initial
>>> review. For this round, I have focused on two changes:
>>> - as suggested by Andreas, we now call the device specific
>>>   code from the generic code to ease the implementation of
>>>   future devices. This is achieved with the addition of
>>>   load/save methods to VirtioDeviceClass.
>>> - virtio subsections now implement a "needed" concept with
>>>   the same semantics as in the VMState code.
>>>
>>> I haven't looked at compat mode issues yet, but it is
>>> on my TODO list.
>>
>> If you fix up the comments to be either
>>
>>   /*
>>    * foo
>>    */
>>
>> or
>>
>>   /* foo */
>>
>> style, not
>>
>>   /* foo
>>    */
>>
>> then you get my
>>
>>
>> Acked-by: Alexander Graf <agraf@suse.de>
>>
>>
>> Alex
> 
> Documented anywhere?
> Linux style is
> 
>         /* Always
>          * like this.
>          */
> 
> so it's definitely not universal.

I could've sworn that you (mst) asked at least two people to change
comments from

/* foo
   bar */

to

/*
 * foo
 */

style...

Andreas

-- 
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany
GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg

Re: [Qemu-devel] [PATCH RFC V2 0/8] virtio: migrate new properties

[Michael S. Tsirkin]

On Mon, May 19, 2014 at 05:40:36PM +0200, Andreas Färber wrote:
> Am 19.05.2014 17:10, schrieb Michael S. Tsirkin:
> > On Mon, May 19, 2014 at 02:02:39PM +0200, Alexander Graf wrote:
> >>
> >> On 19.05.14 10:38, Greg Kurz wrote:
> >>> Hi,
> >>>
> >>> This patch set tries to address comments from the initial
> >>> review. For this round, I have focused on two changes:
> >>> - as suggested by Andreas, we now call the device specific
> >>>   code from the generic code to ease the implementation of
> >>>   future devices. This is achieved with the addition of
> >>>   load/save methods to VirtioDeviceClass.
> >>> - virtio subsections now implement a "needed" concept with
> >>>   the same semantics as in the VMState code.
> >>>
> >>> I haven't looked at compat mode issues yet, but it is
> >>> on my TODO list.
> >>
> >> If you fix up the comments to be either
> >>
> >>   /*
> >>    * foo
> >>    */
> >>
> >> or
> >>
> >>   /* foo */
> >>
> >> style, not
> >>
> >>   /* foo
> >>    */
> >>
> >> then you get my
> >>
> >>
> >> Acked-by: Alexander Graf <agraf@suse.de>
> >>
> >>
> >> Alex
> > 
> > Documented anywhere?
> > Linux style is
> > 
> >         /* Always
> >          * like this.
> >          */
> > 
> > so it's definitely not universal.
> 
> I could've sworn that you (mst) asked at least two people to change
> comments from
> 
> /* foo
>    bar */
> 
> to
> 
> /*
>  * foo
>  */
> 
> style...
> 
> Andreas

IMHO it's the last */ on the same line as text that looks ugly.
 /*
  * foo
  */

/* foo */

/* foo
 */

all look ok I think.


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