Re: [PATCH 3/3] vhost_vdpa: support PACKED when setting-getting vring_base

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On Sat, Apr 22, 2023 at 3:57 AM Shannon Nelson <shannon.nelson@xxxxxxx> wrote:
>
> Use the right structs for PACKED or split vqs when setting and
> getting the vring base.
>
> Signed-off-by: Shannon Nelson <shannon.nelson@xxxxxxx>
> ---
>  drivers/vhost/vdpa.c | 19 +++++++++++++++----
>  1 file changed, 15 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index 599b8cc238c7..2543ae9d5939 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -585,7 +585,12 @@ static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
>                 if (r)
>                         return r;
>
> -               vq->last_avail_idx = vq_state.split.avail_index;
> +               if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
> +                       vq->last_avail_idx = vq_state.packed.last_avail_idx;
> +                       vq->last_used_idx = vq_state.packed.last_used_idx;

I wonder if the compiler will guarantee a piggyback for the wrap
counter here? If not, should we explicitly packing wrap counter?

Thanks

> +               } else {
> +                       vq->last_avail_idx = vq_state.split.avail_index;
> +               }
>                 break;
>         }
>
> @@ -603,9 +608,15 @@ static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
>                 break;
>
>         case VHOST_SET_VRING_BASE:
> -               vq_state.split.avail_index = vq->last_avail_idx;
> -               if (ops->set_vq_state(vdpa, idx, &vq_state))
> -                       r = -EINVAL;
> +               if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
> +                       vq_state.packed.last_avail_idx = vq->last_avail_idx & 0x7fff;
> +                       vq_state.packed.last_avail_counter = !!(vq->last_avail_idx & 0x8000);
> +                       vq_state.packed.last_used_idx = vq->last_used_idx & 0x7fff;
> +                       vq_state.packed.last_used_counter = !!(vq->last_used_idx & 0x8000);
> +               } else {
> +                       vq_state.split.avail_index = vq->last_avail_idx;
> +               }
> +               r = ops->set_vq_state(vdpa, idx, &vq_state);
>                 break;
>
>         case VHOST_SET_VRING_CALL:
> --
> 2.17.1
>

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