Re: [Qemu-devel] live migration between qemu-kvm 1.0 and 0.15

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2012-03-27 18:49, Anthony Liguori wrote:
> On 03/27/2012 11:46 AM, Avi Kivity wrote:
>> On 03/27/2012 06:39 PM, Anthony Liguori wrote:
>>>
>>> So, since we're approaching 1.1, we should really discuss release
>>> criteria for 1.1 with respect to live migration.  I'd prefer to avoid
>>> surprises in this release.
>>
>> Agree strongly.
>>
>>>
>>> My expectation is that migration works from:
>>>
>>> qemu-1.0 -M 1.0     =>     qemu-1.1 -M 1.1
>>
>> Why do you expect that?  Maybe you meant -M 1.0 at the end?
> 
> Sorry, I did mean -M 1.0.
> 
>>
>>> qemu-1.1 -M 1.0<=    qemu-1.1 -M 1.0
>>>
>>> I would expect that migration works from:
>>>
>>> qemu-0.15 -M 0.15   =>    qemu-1.1 -M 0.15
>>>
>>
>> Ack.
>>
>>> I'm okay if this fails gracefully:
>>>
>>> qemu-1.1 -M 0.15<=   qemu-0.15 -M 0.15
>>
>> RHEL has more stringent requirements (going back to its heavily patched
>> 0.12).  I think we should have the infrastructure that allow one to add
>> the hacks to make this work, even if we don't actually do the compat
>> work for the release (I think it's fine for qemu to support just one
>> version going back; and unreasonable to require it to go as far back as
>> RHEL).
> 
> This is reasonable to me.

Here is a draft to get things written in the old format. Totally
untested and likely borken (written in a hurry). I'll split up if it
works fine.

Jan

diff --git a/hw/fdc.c b/hw/fdc.c
index a0236b7..bf0e59d 100644
--- a/hw/fdc.c
+++ b/hw/fdc.c
@@ -1981,7 +1981,7 @@ static int isabus_fdc_init1(ISADevice *dev)
     isa_init_irq(&isa->busdev, &fdctrl->irq, isairq);
     fdctrl->dma_chann = dma_chann;
 
-    qdev_set_legacy_instance_id(&dev->qdev, iobase, 2);
+    qdev_set_legacy_instance_id(&dev->qdev, iobase, 2, false);
     ret = fdctrl_init_common(fdctrl);
 
     add_boot_device_path(isa->bootindexA, &dev->qdev, "/floppy@0");
@@ -2002,7 +2002,7 @@ static int sysbus_fdc_init1(SysBusDevice *dev)
     qdev_init_gpio_in(&dev->qdev, fdctrl_handle_tc, 1);
     fdctrl->dma_chann = -1;
 
-    qdev_set_legacy_instance_id(&dev->qdev, 0 /* io */, 2); /* FIXME */
+    qdev_set_legacy_instance_id(&dev->qdev, 0 /* io */, 2, false); /* FIXME */
     ret = fdctrl_init_common(fdctrl);
 
     return ret;
@@ -2019,7 +2019,7 @@ static int sun4m_fdc_init1(SysBusDevice *dev)
     qdev_init_gpio_in(&dev->qdev, fdctrl_handle_tc, 1);
 
     fdctrl->sun4m = 1;
-    qdev_set_legacy_instance_id(&dev->qdev, 0 /* io */, 2); /* FIXME */
+    qdev_set_legacy_instance_id(&dev->qdev, 0 /* io */, 2, false); /* FIXME */
     return fdctrl_init_common(fdctrl);
 }
 
diff --git a/hw/i8254_common.c b/hw/i8254_common.c
index a03d7cd..b8d0d55 100644
--- a/hw/i8254_common.c
+++ b/hw/i8254_common.c
@@ -179,7 +179,7 @@ static int pit_init_common(ISADevice *dev)
 
     isa_register_ioport(dev, &pit->ioports, pit->iobase);
 
-    qdev_set_legacy_instance_id(&dev->qdev, pit->iobase, 2);
+    qdev_set_legacy_instance_id(&dev->qdev, pit->iobase, 2, false);
 
     return 0;
 }
diff --git a/hw/i8259_common.c b/hw/i8259_common.c
index ab3d98b..e37fab6 100644
--- a/hw/i8259_common.c
+++ b/hw/i8259_common.c
@@ -78,7 +78,8 @@ static int pic_init_common(ISADevice *dev)
         isa_register_ioport(NULL, &s->elcr_io, s->elcr_addr);
     }
 
-    qdev_set_legacy_instance_id(&s->dev.qdev, s->iobase, 1);
+    qdev_set_legacy_instance_id(&s->dev.qdev, s->iobase, 1,
+                                s->compat_instance_id);
 
     return 0;
 }
@@ -130,6 +131,8 @@ static Property pic_properties_common[] = {
     DEFINE_PROP_HEX32("elcr_addr", PICCommonState, elcr_addr,  -1),
     DEFINE_PROP_HEX8("elcr_mask", PICCommonState, elcr_mask,  -1),
     DEFINE_PROP_BIT("master", PICCommonState, master,  0, false),
+    DEFINE_PROP_BIT("compat_instance_id", PICCommonState, compat_instance_id,
+                    0, false),
     DEFINE_PROP_END_OF_LIST(),
 };
 
diff --git a/hw/i8259_internal.h b/hw/i8259_internal.h
index 4137b61..a47668d 100644
--- a/hw/i8259_internal.h
+++ b/hw/i8259_internal.h
@@ -70,6 +70,7 @@ struct PICCommonState {
     uint32_t master; /* reflects /SP input pin */
     uint32_t iobase;
     uint32_t elcr_addr;
+    uint32_t compat_instance_id;
     MemoryRegion base_io;
     MemoryRegion elcr_io;
 };
diff --git a/hw/mc146818rtc.c b/hw/mc146818rtc.c
index 2b59c36..3b0e07c 100644
--- a/hw/mc146818rtc.c
+++ b/hw/mc146818rtc.c
@@ -697,7 +697,7 @@ static int rtc_initfn(ISADevice *dev)
     memory_region_init_io(&s->io, &cmos_ops, s, "rtc", 2);
     isa_register_ioport(dev, &s->io, base);
 
-    qdev_set_legacy_instance_id(&dev->qdev, base, 2);
+    qdev_set_legacy_instance_id(&dev->qdev, base, 2, false);
     qemu_register_reset(rtc_reset, s);
 
     object_property_add(OBJECT(s), "date", "struct tm",
diff --git a/hw/pc_piix.c b/hw/pc_piix.c
index 3f99f9a..4c8d591 100644
--- a/hw/pc_piix.c
+++ b/hw/pc_piix.c
@@ -386,6 +386,10 @@ static QEMUMachine pc_machine_v1_0 = {
             .driver   = "isa-fdc",
             .property = "check_media_rate",
             .value    = "off",
+        },{
+            .driver   = "i8259",
+            .property = "compat_instance_id",
+            .value    = "on",
         },
         { /* end of list */ }
     },
@@ -405,6 +409,10 @@ static QEMUMachine pc_machine_v0_15 = {
             .driver   = "isa-fdc",
             .property = "check_media_rate",
             .value    = "off",
+        },{
+            .driver   = "i8259",
+            .property = "compat_instance_id",
+            .value    = "on",
         },
         { /* end of list */ }
     },
@@ -449,6 +457,10 @@ static QEMUMachine pc_machine_v0_14 = {
             .driver   = "pc-sysfw",
             .property = "rom_only",
             .value    = stringify(1),
+        },{
+            .driver   = "i8259",
+            .property = "compat_instance_id",
+            .value    = "on",
         },
         { /* end of list */ }
     },
@@ -505,6 +517,10 @@ static QEMUMachine pc_machine_v0_13 = {
             .driver   = "pc-sysfw",
             .property = "rom_only",
             .value    = stringify(1),
+        },{
+            .driver   = "i8259",
+            .property = "compat_instance_id",
+            .value    = "on",
         },
         { /* end of list */ }
     },
@@ -565,6 +581,10 @@ static QEMUMachine pc_machine_v0_12 = {
             .driver   = "pc-sysfw",
             .property = "rom_only",
             .value    = stringify(1),
+        },{
+            .driver   = "i8259",
+            .property = "compat_instance_id",
+            .value    = "on",
         },
         { /* end of list */ }
     }
@@ -633,6 +653,10 @@ static QEMUMachine pc_machine_v0_11 = {
             .driver   = "pc-sysfw",
             .property = "rom_only",
             .value    = stringify(1),
+        },{
+            .driver   = "i8259",
+            .property = "compat_instance_id",
+            .value    = "on",
         },
         { /* end of list */ }
     }
@@ -713,6 +737,10 @@ static QEMUMachine pc_machine_v0_10 = {
             .driver   = "pc-sysfw",
             .property = "rom_only",
             .value    = stringify(1),
+        },{
+            .driver   = "i8259",
+            .property = "compat_instance_id",
+            .value    = "on",
         },
         { /* end of list */ }
     },
diff --git a/hw/qdev.c b/hw/qdev.c
index ee21d90..7f54ecf 100644
--- a/hw/qdev.c
+++ b/hw/qdev.c
@@ -155,7 +155,8 @@ int qdev_init(DeviceState *dev)
     if (qdev_get_vmsd(dev)) {
         vmstate_register_with_alias_id(dev, -1, qdev_get_vmsd(dev), dev,
                                        dev->instance_id_alias,
-                                       dev->alias_required_for_version);
+                                       dev->alias_required_for_version,
+                                       dev->write_alias_id);
     }
     dev->state = DEV_STATE_INITIALIZED;
     if (dev->hotplugged) {
@@ -165,11 +166,13 @@ int qdev_init(DeviceState *dev)
 }
 
 void qdev_set_legacy_instance_id(DeviceState *dev, int alias_id,
-                                 int required_for_version)
+                                 int required_for_version,
+                                 bool write_alias_id)
 {
     assert(dev->state == DEV_STATE_CREATED);
     dev->instance_id_alias = alias_id;
     dev->alias_required_for_version = required_for_version;
+    dev->write_alias_id = write_alias_id;
 }
 
 int qdev_unplug(DeviceState *dev)
diff --git a/hw/qdev.h b/hw/qdev.h
index 9cc3f98..3917020 100644
--- a/hw/qdev.h
+++ b/hw/qdev.h
@@ -76,6 +76,7 @@ struct DeviceState {
     QTAILQ_ENTRY(DeviceState) sibling;
     int instance_id_alias;
     int alias_required_for_version;
+    bool write_alias_id;
 };
 
 typedef void (*bus_dev_printfn)(Monitor *mon, DeviceState *dev, int indent);
@@ -147,7 +148,8 @@ DeviceState *qdev_device_add(QemuOpts *opts);
 int qdev_init(DeviceState *dev) QEMU_WARN_UNUSED_RESULT;
 void qdev_init_nofail(DeviceState *dev);
 void qdev_set_legacy_instance_id(DeviceState *dev, int alias_id,
-                                 int required_for_version);
+                                 int required_for_version,
+                                 bool write_alias_id);
 int qdev_unplug(DeviceState *dev);
 void qdev_free(DeviceState *dev);
 int qdev_simple_unplug_cb(DeviceState *dev);
diff --git a/hw/serial.c b/hw/serial.c
index c0ee55d..20adf98 100644
--- a/hw/serial.c
+++ b/hw/serial.c
@@ -789,7 +789,7 @@ static int serial_isa_initfn(ISADevice *dev)
     s->baudbase = 115200;
     isa_init_irq(dev, &s->irq, isa->isairq);
     serial_init_core(s);
-    qdev_set_legacy_instance_id(&dev->qdev, isa->iobase, 3);
+    qdev_set_legacy_instance_id(&dev->qdev, isa->iobase, 3, false);
 
     memory_region_init_io(&s->io, &serial_io_ops, s, "serial", 8);
     isa_register_ioport(dev, &s->io, isa->iobase);
diff --git a/savevm.c b/savevm.c
index 12fb209..2f53864 100644
--- a/savevm.c
+++ b/savevm.c
@@ -1179,6 +1179,7 @@ typedef struct SaveStateEntry {
     CompatEntry *compat;
     int no_migrate;
     int is_ram;
+    bool write_alias_id;
 } SaveStateEntry;
 
 
@@ -1316,7 +1317,8 @@ void unregister_savevm(DeviceState *dev, const char *idstr, void *opaque)
 int vmstate_register_with_alias_id(DeviceState *dev, int instance_id,
                                    const VMStateDescription *vmsd,
                                    void *opaque, int alias_id,
-                                   int required_for_version)
+                                   int required_for_version,
+                                   bool write_alias_id)
 {
     SaveStateEntry *se;
 
@@ -1332,6 +1334,7 @@ int vmstate_register_with_alias_id(DeviceState *dev, int instance_id,
     se->opaque = opaque;
     se->vmsd = vmsd;
     se->alias_id = alias_id;
+    se->write_alias_id = write_alias_id;
     se->no_migrate = vmsd->unmigratable;
 
     if (dev && dev->parent_bus && dev->parent_bus->info->get_dev_path) {
@@ -1365,7 +1368,7 @@ int vmstate_register(DeviceState *dev, int instance_id,
                      const VMStateDescription *vmsd, void *opaque)
 {
     return vmstate_register_with_alias_id(dev, instance_id, vmsd,
-                                          opaque, -1, 0);
+                                          opaque, -1, 0, false);
 }
 
 void vmstate_unregister(DeviceState *dev, const VMStateDescription *vmsd,
@@ -1591,7 +1594,7 @@ int qemu_savevm_state_begin(QEMUFile *f, int blk_enable, int shared)
         qemu_put_byte(f, len);
         qemu_put_buffer(f, (uint8_t *)se->idstr, len);
 
-        qemu_put_be32(f, se->instance_id);
+        qemu_put_be32(f, se->write_alias_id ? se->alias_id : se->instance_id);
         qemu_put_be32(f, se->version_id);
 
         ret = se->save_live_state(f, QEMU_VM_SECTION_START, se->opaque);
@@ -1683,7 +1686,7 @@ int qemu_savevm_state_complete(QEMUFile *f)
         qemu_put_byte(f, len);
         qemu_put_buffer(f, (uint8_t *)se->idstr, len);
 
-        qemu_put_be32(f, se->instance_id);
+        qemu_put_be32(f, se->write_alias_id ? se->alias_id : se->instance_id);
         qemu_put_be32(f, se->version_id);
 
         vmstate_save(f, se);
@@ -1762,7 +1765,7 @@ static int qemu_save_device_state(QEMUFile *f)
         qemu_put_byte(f, len);
         qemu_put_buffer(f, (uint8_t *)se->idstr, len);
 
-        qemu_put_be32(f, se->instance_id);
+        qemu_put_be32(f, se->write_alias_id ? se->alias_id : se->instance_id);
         qemu_put_be32(f, se->version_id);
 
         vmstate_save(f, se);
diff --git a/vmstate.h b/vmstate.h
index 82d97ae..34b78d8 100644
--- a/vmstate.h
+++ b/vmstate.h
@@ -605,7 +605,8 @@ int vmstate_register(DeviceState *dev, int instance_id,
 int vmstate_register_with_alias_id(DeviceState *dev, int instance_id,
                                    const VMStateDescription *vmsd,
                                    void *base, int alias_id,
-                                   int required_for_version);
+                                   int required_for_version,
+                                   bool write_alias_id);
 void vmstate_unregister(DeviceState *dev, const VMStateDescription *vmsd,
                         void *opaque);
 

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