Re: [PATCH for-8.2 v2 6/6] vfio/migration: Allow migration of multiple P2P supporting devices

[Cédric Le Goater]

On 7/31/23 12:25, Avihai Horon wrote:
> Now that P2P support has been added to VFIO migration, allow migration
> of multiple devices if all of them support P2P migration.
>
> Single device migration is allowed regardless of P2P migration support.
>
> Signed-off-by: Avihai Horon <avihaih@nvidia.com>
> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>


Reviewed-by: Cédric Le Goater <clg@redhat.com>

Thanks,

C.


> ---
>   hw/vfio/common.c | 26 ++++++++++++++++++--------
>   1 file changed, 18 insertions(+), 8 deletions(-)
>
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index 7c3d636025..8a8d074e18 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -363,21 +363,31 @@ bool vfio_mig_active(void)
>   
>   static Error *multiple_devices_migration_blocker;
>   
> -static unsigned int vfio_migratable_device_num(void)
> +/*
> + * Multiple devices migration is allowed only if all devices support P2P
> + * migration. Single device migration is allowed regardless of P2P migration
> + * support.
> + */
> +static bool vfio_multiple_devices_migration_is_supported(void)
>   {
>       VFIOGroup *group;
>       VFIODevice *vbasedev;
>       unsigned int device_num = 0;
> +    bool all_support_p2p = true;
>   
>       QLIST_FOREACH(group, &vfio_group_list, next) {
>           QLIST_FOREACH(vbasedev, &group->device_list, next) {
>               if (vbasedev->migration) {
>                   device_num++;
> +
> +                if (!(vbasedev->migration->mig_flags & VFIO_MIGRATION_P2P)) {
> +                    all_support_p2p = false;
> +                }
>               }
>           }
>       }
>   
> -    return device_num;
> +    return all_support_p2p || device_num <= 1;
>   }
>   
>   int vfio_block_multiple_devices_migration(VFIODevice *vbasedev, Error **errp)
> @@ -385,19 +395,19 @@ int vfio_block_multiple_devices_migration(VFIODevice 
> *vbasedev, Error **errp)
>       int ret;
>   
>       if (multiple_devices_migration_blocker ||
> -        vfio_migratable_device_num() <= 1) {
> +        vfio_multiple_devices_migration_is_supported()) {
>           return 0;
>       }
>   
>       if (vbasedev->enable_migration == ON_OFF_AUTO_ON) {
> -        error_setg(errp, "Migration is currently not supported with multiple "
> -                         "VFIO devices");
> +        error_setg(errp, "Multiple VFIO devices migration is supported only if 
> "
> +                         "all of them support P2P migration");
>           return -EINVAL;
>       }
>   
>       error_setg(&multiple_devices_migration_blocker,
> -               "Migration is currently not supported with multiple "
> -               "VFIO devices");
> +               "Multiple VFIO devices migration is supported only if all of "
> +               "them support P2P migration");
>       ret = migrate_add_blocker(multiple_devices_migration_blocker, errp);
>       if (ret < 0) {
>           error_free(multiple_devices_migration_blocker);
> @@ -410,7 +420,7 @@ int vfio_block_multiple_devices_migration(VFIODevice 
> *vbasedev, Error **errp)
>   void vfio_unblock_multiple_devices_migration(void)
>   {
>       if (!multiple_devices_migration_blocker ||
> -        vfio_migratable_device_num() > 1) {
> +        !vfio_multiple_devices_migration_is_supported()) {
>           return;
>       }
>