Re: [PATCH RFC 4/4] vhost-vdpa: introduce IOTLB_PERSIST backend feature bit

[Jason Wang]

On Tue, Aug 15, 2023 at 9:45 AM Si-Wei Liu <si-wei.liu@xxxxxxxxxx> wrote:
>
> Signed-off-by: Si-Wei Liu <si-wei.liu@xxxxxxxxxx>
> ---
>  drivers/vhost/vdpa.c             | 16 +++++++++++++++-
>  include/uapi/linux/vhost_types.h |  2 ++
>  2 files changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index 62b0a01..75092a7 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -406,6 +406,14 @@ static bool vhost_vdpa_can_resume(const struct vhost_vdpa *v)
>         return ops->resume;
>  }
>
> +static bool vhost_vdpa_has_persistent_map(const struct vhost_vdpa *v)
> +{
> +       struct vdpa_device *vdpa = v->vdpa;
> +       const struct vdpa_config_ops *ops = vdpa->config;
> +
> +       return (!ops->set_map && !ops->dma_map) || ops->reset_map;

So this means the IOTLB/IOMMU mappings have already been decoupled
from the vdpa reset. So it should have been noticed by the userspace.
I guess we can just fix the simulator and mlx5 then we are fine?

Thanks