Re: [PATCH v4 15/15] vfio/common: Block migration with vIOMMUs without address width limits

["Duan, Zhenzhong" <zhenzhong.duan@intel.com>]

On 6/23/2023 5:48 AM, Joao Martins wrote:
> Only block the case when the underlying vIOMMU model does not report any
> address space limits, in addition to DMA translation being off or no
> vIOMMU present. The limits are needed such that can define the IOVA limits
> that arm the device dirty tracker.
>
> Additionally, reword the migration blocker error message to clarify that
> we the configured vIOMMU does not support migration, as opposed to
> implying that just being there blocks migration.
>
> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
> ---
>   hw/vfio/common.c | 7 +++++--
>   1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index 62f91e8e102d..c3cc0dd47044 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -449,15 +449,18 @@ static int vfio_viommu_get_max_iova(hwaddr *max_iova)
>   
>   int vfio_block_giommu_migration(Error **errp)
>   {
> +    hwaddr max;
>       int ret;
>   
>       if (giommu_migration_blocker ||
> -        !vfio_viommu_preset()) {
> +        !vfio_viommu_preset() ||
> +        (vfio_viommu_preset() && !vfio_viommu_get_max_iova(&max))) {

Could be simplified as below:

+        !vfio_viommu_preset() || !vfio_viommu_get_max_iova(&max))) {

Thanks
Zhenzhong