Re: [PATCH 3/6] vfio/migration: Add vfio_migratable_devices_num()

[Cédric Le Goater]

On 8/28/23 17:18, Avihai Horon wrote:
> Add vfio_migratable_devices_num() function, which returns the number of
> VFIO devices that are using VFIO migration, and use it in
> vfio_multiple_devices_migration_is_supported().
>
> This is done in preparation for next patches which will block VFIO
> migration with postcopy migration or background snapshot, as they are
> not compatible together.
>
> Signed-off-by: Avihai Horon <avihaih@nvidia.com>


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

Thanks,

C.


> ---
>   hw/vfio/common.c | 22 ++++++++++++++++++----
>   1 file changed, 18 insertions(+), 4 deletions(-)
>
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index 237101d038..57a76feab1 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -363,6 +363,23 @@ bool vfio_mig_active(void)
>   
>   static Error *multiple_devices_migration_blocker;
>   
> +static unsigned int vfio_migratable_devices_num(void)
> +{
> +    VFIOGroup *group;
> +    VFIODevice *vbasedev;
> +    unsigned int device_num = 0;
> +
> +    QLIST_FOREACH(group, &vfio_group_list, next) {
> +        QLIST_FOREACH(vbasedev, &group->device_list, next) {
> +            if (vbasedev->migration) {
> +                device_num++;
> +            }
> +        }
> +    }
> +
> +    return device_num;
> +}
> +
>   /*
>    * Multiple devices migration is allowed only if all devices support P2P
>    * migration. Single device migration is allowed regardless of P2P migration
> @@ -372,14 +389,11 @@ 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;
>                   }
> @@ -387,7 +401,7 @@ static bool 
> vfio_multiple_devices_migration_is_supported(void)
>           }
>       }
>   
> -    return all_support_p2p || device_num <= 1;
> +    return all_support_p2p || vfio_migratable_devices_num() <= 1;
>   }
>   
>   int vfio_block_multiple_devices_migration(VFIODevice *vbasedev, Error **errp)