[Qemu-devel] [PATCH v4] Add machine parameter qemu-kvm-migration for live migrate compatibility with qemu-kvm

[Alex Bligh <alex@alex.org.uk>]

Add a machine parameter qemu-kvm-migration for live migrate compatibility
with qemu-kvm version 1.0. Usage:
    -machine pc-1.0,qemu-kvm-migration=on

This has three effects:
1. cirrus-vga.vgamem_mb defaults to 16 rather than 8
2. A type 2 piix4_pm record is interpreted as being type 3
3. A type 2 i8254 PIT common state is interpreted as being type 3

Signed-off-by: Alex Bligh <alex@alex.org.uk>
---
 hw/acpi/piix4.c         |   47 +++++++++++++++++++++++++++++++++++++++++++++--
 hw/core/machine.c       |   16 ++++++++++++++++
 hw/i386/pc.c            |    1 +
 hw/i386/pc_piix.c       |   25 +++++++++++++++++++++++++
 hw/timer/i8254_common.c |   11 ++++++++++-
 include/hw/boards.h     |    7 +++++++
 vl.c                    |    7 +++++++
 7 files changed, 111 insertions(+), 3 deletions(-)

diff --git a/hw/acpi/piix4.c b/hw/acpi/piix4.c
index b72b34e..3c9da23 100644
--- a/hw/acpi/piix4.c
+++ b/hw/acpi/piix4.c
@@ -200,12 +200,26 @@ static const VMStateDescription vmstate_pci_status = {
     }
 };
 
+static const VMStateDescription vmstate_acpi_compat;
+
 static int acpi_load_old(QEMUFile *f, void *opaque, int version_id)
 {
     PIIX4PMState *s = opaque;
     int ret, i;
     uint16_t temp;
 
+    /* If we are expecting the inbound migration to come from
+     * qemu-kvm 1.0, it will have a version_id of 2 but really
+     * be version 3, so call back the original vmstate_load_state
+     * with a different more tolerant vmstate descriptor
+     */
+    if ((version_id == 2) &&
+        qemu_opt_get_bool(qemu_get_machine_opts(), "qemu-kvm-migration",
+                          DEFAULT_QEMU_KVM_MIGRATION)) {
+        return vmstate_load_state(f, &vmstate_acpi_compat,
+                                  opaque, version_id);
+    }
+
     ret = pci_device_load(PCI_DEVICE(s), f);
     if (ret < 0) {
         return ret;
@@ -267,8 +281,9 @@ static const VMStateDescription vmstate_memhp_state = {
 };
 
 /* qemu-kvm 1.2 uses version 3 but advertised as 2
- * To support incoming qemu-kvm 1.2 migration, change version_id
- * and minimum_version_id to 2 below (which breaks migration from
+ * To support incoming qemu-kvm 1.2 migration, we support
+ * via a command line option a change to minimum_version_id
+ * of 2 in a _compat structure (which breaks migration from
  * qemu 1.2).
  *
  */
@@ -307,6 +322,34 @@ static const VMStateDescription vmstate_acpi = {
     }
 };
 
+static const VMStateDescription vmstate_acpi_compat = {
+    .name = "piix4_pm",
+    .version_id = 3,
+    .minimum_version_id = 2,
+    .minimum_version_id_old = 1,
+    .load_state_old = NULL, /* to avoid recursion */
+    .post_load = vmstate_acpi_post_load,
+    .fields      = (VMStateField[]) {
+        VMSTATE_PCI_DEVICE(parent_obj, PIIX4PMState),
+        VMSTATE_UINT16(ar.pm1.evt.sts, PIIX4PMState),
+        VMSTATE_UINT16(ar.pm1.evt.en, PIIX4PMState),
+        VMSTATE_UINT16(ar.pm1.cnt.cnt, PIIX4PMState),
+        VMSTATE_STRUCT(apm, PIIX4PMState, 0, vmstate_apm, APMState),
+        VMSTATE_TIMER(ar.tmr.timer, PIIX4PMState),
+        VMSTATE_INT64(ar.tmr.overflow_time, PIIX4PMState),
+        VMSTATE_STRUCT(ar.gpe, PIIX4PMState, 2, vmstate_gpe, ACPIGPE),
+        VMSTATE_STRUCT_TEST(
+            acpi_pci_hotplug.acpi_pcihp_pci_status[ACPI_PCIHP_BSEL_DEFAULT],
+            PIIX4PMState,
+            vmstate_test_no_use_acpi_pci_hotplug,
+            2, vmstate_pci_status,
+            struct AcpiPciHpPciStatus),
+        VMSTATE_PCI_HOTPLUG(acpi_pci_hotplug, PIIX4PMState,
+                            vmstate_test_use_acpi_pci_hotplug),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 static void piix4_reset(void *opaque)
 {
     PIIX4PMState *s = opaque;
diff --git a/hw/core/machine.c b/hw/core/machine.c
index 7a66c57..bbccba9 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -235,6 +235,20 @@ static void machine_set_firmware(Object *obj, const char *value, Error **errp)
     ms->firmware = g_strdup(value);
 }
 
+static bool machine_get_qemu_kvm_migration(Object *obj, Error **errp)
+{
+    MachineState *ms = MACHINE(obj);
+
+    return ms->qemu_kvm_migration;
+}
+
+static void machine_set_qemu_kvm_migration(Object *obj, bool value, Error **errp)
+{
+    MachineState *ms = MACHINE(obj);
+
+    ms->qemu_kvm_migration = value;
+}
+
 static void machine_initfn(Object *obj)
 {
     object_property_add_str(obj, "accel",
@@ -274,6 +288,8 @@ static void machine_initfn(Object *obj)
     object_property_add_bool(obj, "usb", machine_get_usb, machine_set_usb, NULL);
     object_property_add_str(obj, "firmware",
                             machine_get_firmware, machine_set_firmware, NULL);
+    object_property_add_bool(obj, "qemu-kvm-migration",
+                             machine_get_qemu_kvm_migration, machine_set_qemu_kvm_migration, NULL);
 }
 
 static void machine_finalize(Object *obj)
diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 2cf22b1..c74f2f9 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -1516,6 +1516,7 @@ static void pc_generic_machine_class_init(ObjectClass *oc, void *data)
     mc->alias = qm->alias;
     mc->desc = qm->desc;
     mc->init = qm->init;
+    mc->earlyinit = qm->earlyinit;
     mc->reset = qm->reset;
     mc->hot_add_cpu = qm->hot_add_cpu;
     mc->kvm_type = qm->kvm_type;
diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
index 7081c08..0f122e2 100644
--- a/hw/i386/pc_piix.c
+++ b/hw/i386/pc_piix.c
@@ -386,6 +386,21 @@ static void pc_init_pci_1_2(MachineState *machine)
     pc_init_pci(machine);
 }
 
+static void pc_early_init_pci_1_0(MachineState *machine)
+{
+    /* default value of cirrus-vga.vgamem_mb should be 16 if migrating from qemu-kvm */
+    if (qemu_opt_get_bool(qemu_get_machine_opts(), "qemu-kvm-migration",
+                          DEFAULT_QEMU_KVM_MIGRATION)) {
+        GlobalProperty *gp;
+        MachineClass *mc = MACHINE_GET_CLASS(machine);
+        for (gp = mc->compat_props; gp->driver; gp++) {
+            if (!strcmp(gp->driver, "cirrus-vga") && !strcmp(gp->property, "vgamem_mb")) {
+                gp->value = stringify(16);
+            }
+        }
+    }
+}
+
 /* PC init function for pc-0.10 to pc-0.13 */
 static void pc_init_pci_no_kvmclock(MachineState *machine)
 {
@@ -614,6 +629,11 @@ static QEMUMachine pc_machine_v1_1 = {
     },
 };
 
+/* NB cirrus-vga default value is 8MB anyway, save if we
+ * monkey patch it to change the default when the qemu-kvm-migration
+ * machine parameter is selected
+ */
+
 #define PC_COMPAT_1_0 \
         PC_COMPAT_1_1,\
         {\
@@ -632,10 +652,15 @@ static QEMUMachine pc_machine_v1_1 = {
             .driver   = TYPE_USB_DEVICE,\
             .property = "full-path",\
             .value    = "no",\
+        },{\
+            .driver   = "cirrus-vga",\
+            .property = "vgamem_mb",\
+            .value    = stringify(8),\
         }
 
 static QEMUMachine pc_machine_v1_0 = {
     PC_I440FX_1_2_MACHINE_OPTIONS,
+    .earlyinit = pc_early_init_pci_1_0,
     .name = "pc-1.0",
     .compat_props = (GlobalProperty[]) {
         PC_COMPAT_1_0,
diff --git a/hw/timer/i8254_common.c b/hw/timer/i8254_common.c
index 07345f6..0342e93 100644
--- a/hw/timer/i8254_common.c
+++ b/hw/timer/i8254_common.c
@@ -257,6 +257,14 @@ static int pit_dispatch_post_load(void *opaque, int version_id)
     return 0;
 }
 
+static bool has_irq_disabled(void *opaque, int version_id)
+{
+    return (version_id >= 3) ||
+        ((version_id == 2) &&
+         qemu_opt_get_bool(qemu_get_machine_opts(), "qemu-kvm-migration",
+                           DEFAULT_QEMU_KVM_MIGRATION));
+}
+
 static const VMStateDescription vmstate_pit_common = {
     .name = "i8254",
     .version_id = 3,
@@ -266,7 +274,8 @@ static const VMStateDescription vmstate_pit_common = {
     .pre_save = pit_dispatch_pre_save,
     .post_load = pit_dispatch_post_load,
     .fields = (VMStateField[]) {
-        VMSTATE_UINT32_V(channels[0].irq_disabled, PITCommonState, 3),
+        VMSTATE_UINT32_TEST(channels[0].irq_disabled, PITCommonState,
+                            has_irq_disabled),
         VMSTATE_STRUCT_ARRAY(channels, PITCommonState, 3, 2,
                              vmstate_pit_channel, PITChannelState),
         VMSTATE_INT64(channels[0].next_transition_time,
diff --git a/include/hw/boards.h b/include/hw/boards.h
index 605a970..ffde5dd 100644
--- a/include/hw/boards.h
+++ b/include/hw/boards.h
@@ -13,6 +13,8 @@ typedef struct MachineState MachineState;
 
 typedef void QEMUMachineInitFunc(MachineState *ms);
 
+typedef void QEMUMachineEarlyInitFunc(MachineState *ms);
+
 typedef void QEMUMachineResetFunc(void);
 
 typedef void QEMUMachineHotAddCPUFunc(const int64_t id, Error **errp);
@@ -24,6 +26,7 @@ struct QEMUMachine {
     const char *alias;
     const char *desc;
     QEMUMachineInitFunc *init;
+    QEMUMachineEarlyInitFunc *earlyinit;
     QEMUMachineResetFunc *reset;
     QEMUMachineHotAddCPUFunc *hot_add_cpu;
     QEMUMachineGetKvmtypeFunc *kvm_type;
@@ -59,6 +62,8 @@ int qemu_register_machine(QEMUMachine *m);
 #define MACHINE_CLASS(klass) \
     OBJECT_CLASS_CHECK(MachineClass, (klass), TYPE_MACHINE)
 
+#define DEFAULT_QEMU_KVM_MIGRATION false
+
 MachineClass *find_default_machine(void);
 extern MachineState *current_machine;
 
@@ -81,6 +86,7 @@ struct MachineClass {
     const char *desc;
 
     void (*init)(MachineState *state);
+    void (*earlyinit)(MachineState *state);
     void (*reset)(void);
     void (*hot_add_cpu)(const int64_t id, Error **errp);
     int (*kvm_type)(const char *arg);
@@ -123,6 +129,7 @@ struct MachineState {
     bool mem_merge;
     bool usb;
     char *firmware;
+    bool qemu_kvm_migration;
 
     ram_addr_t ram_size;
     ram_addr_t maxram_size;
diff --git a/vl.c b/vl.c
index fe451aa..622afea 100644
--- a/vl.c
+++ b/vl.c
@@ -387,6 +387,10 @@ static QemuOptsList qemu_machine_opts = {
             .name = PC_MACHINE_MAX_RAM_BELOW_4G,
             .type = QEMU_OPT_SIZE,
             .help = "maximum ram below the 4G boundary (32bit boundary)",
+        },{
+            .name = "qemu-kvm-migration",
+            .type = QEMU_OPT_BOOL,
+            .help = "enable/disable migration compatibility from qemu-kvm",
         },
         { /* End of list */ }
     },
@@ -1557,6 +1561,7 @@ static void machine_class_init(ObjectClass *oc, void *data)
     mc->alias = qm->alias;
     mc->desc = qm->desc;
     mc->init = qm->init;
+    mc->earlyinit = qm->earlyinit;
     mc->reset = qm->reset;
     mc->hot_add_cpu = qm->hot_add_cpu;
     mc->kvm_type = qm->kvm_type;
@@ -4003,6 +4008,8 @@ int main(int argc, char **argv, char **envp)
                           OBJECT_CLASS(machine_class))));
     object_property_add_child(object_get_root(), "machine",
                               OBJECT(current_machine), &error_abort);
+    if (machine_class->earlyinit)
+        machine_class->earlyinit(current_machine);
     cpu_exec_init_all();
 
     if (machine_class->hw_version) {
-- 
1.7.9.5