Re: [PATCH v4 11/12] vfio/migration: Don't block migration device dirty tracking is unsupported

[Joao Martins]

On 17/07/2024 03:38, Duan, Zhenzhong wrote:
> 
> 
>> -----Original Message-----
>> From: Joao Martins <joao.m.martins@oracle.com>
>> Subject: [PATCH v4 11/12] vfio/migration: Don't block migration device dirty
>> tracking is unsupported
>>
>> By default VFIO migration is set to auto, which will support live
>> migration if the migration capability is set *and* also dirty page
>> tracking is supported.
>>
>> For testing purposes one can force enable without dirty page tracking
>> via enable-migration=on, but that option is generally left for testing
>> purposes.
>>
>> So starting with IOMMU dirty tracking it can use to acomodate the lack of
>> VF dirty page tracking allowing us to minimize the VF requirements for
>> migration and thus enabling migration by default for those too.
>>
>> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
>> ---
>> hw/vfio/migration.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
>> index 34d4be2ce1b1..ce3d1b6e9a25 100644
>> --- a/hw/vfio/migration.c
>> +++ b/hw/vfio/migration.c
>> @@ -1036,7 +1036,8 @@ bool vfio_migration_realize(VFIODevice
>> *vbasedev, Error **errp)
>>         return !vfio_block_migration(vbasedev, err, errp);
>>     }
>>
>> -    if (!vbasedev->dirty_pages_supported) {
>> +    if (!vbasedev->dirty_pages_supported &&
>> +        !vbasedev->bcontainer->dirty_pages_supported) {
>>         if (vbasedev->enable_migration == ON_OFF_AUTO_AUTO) {
>>             error_setg(&err,
>>                        "%s: VFIO device doesn't support device dirty 
>> tracking",
> 
> I'm not sure if this message needs to be updated, " VFIO device doesn't 
> support device and IOMMU dirty tracking"
> 
> Same for the below:
> 
> warn_report("%s: VFIO device doesn't support device dirty tracking"


Ah yes, good catch. Additionally I think I should check device hwpt rather than
container::dirty_pages_supported i.e.

if (!vbasedev->dirty_pages_supported &&
    (vbasedev->hwpt && !iommufd_hwpt_dirty_tracking(vbasedev->hwpt)))

This makes sure that migration is blocked with more accuracy