On 20/06/2023 04:04, Duan, Zhenzhong wrote:
>> -----Original Message-----
>> From: Avihai Horon <avih...@nvidia.com>
>> Sent: Monday, June 19, 2023 7:14 PM
> ...
>>> a/hw/vfio/migration.c b/hw/vfio/migration.c index
>>> 6b58dddb8859..bc51aa765cb8 100644
>>> --- a/hw/vfio/migration.c
>>> +++ b/hw/vfio/migration.c
>>> @@ -632,42 +632,41 @@ int64_t vfio_mig_bytes_transferred(void)
>>> return bytes_transferred;
>>> }
>>>
>>> -int vfio_migration_realize(VFIODevice *vbasedev, Error **errp)
>>> +bool vfio_migration_realize(VFIODevice *vbasedev, Error **errp)
>>> {
>>> - int ret = -ENOTSUP;
>>> + int ret;
>>>
>>> - if (!vbasedev->enable_migration) {
>>> + if (!vbasedev->enable_migration || vfio_migration_init(vbasedev)) {
>>> + error_setg(&vbasedev->migration_blocker,
>>> + "VFIO device doesn't support migration");
>>> goto add_blocker;
>>> }
>>>
>>> - ret = vfio_migration_init(vbasedev);
>>> - if (ret) {
>>> + if (vfio_block_multiple_devices_migration(errp)) {
>>> + error_setg(&vbasedev->migration_blocker,
>>> + "Migration is currently not supported with multiple "
>>> + "VFIO devices");
>>> goto add_blocker;
>>> }
>>
>> Here you are tying the multiple devices blocker to a specific device.
>> This could be problematic:
>> If you add vfio device #1 and then device #2 then the blocker will be added
>> to
>> device #2. If you then remove device #1, migration will still be blocked
>> although it shouldn't.
>>
>> I think we should keep it as a global blocker and not a per-device blocker.
>
> Thanks for point out, you are right, seems I need to restore the multiple
> devices part code.
It's the same for vIOMMU migration blocker. You could have a machine with
default_bus_bypass_iommu=on and add device #1 with bypass_iommu=off attribute in
pxb PCI port, and then add device #2 with bypass_iommu=on. The blocker is added
because of device #1 but then it will remain blocked if you remove it.
