linux-kernel - Re: [PATCH 18/19] virtio_ring: factor out split indirect detaching logic

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Message-ID: <CAJaqyWeDOjsJ1wv7PvXt86JztEVMuwKSR1-g9NS35DUbopK8ag@mail.gmail.com>
Date: Wed, 26 Mar 2025 15:02:12 +0100
From: Eugenio Perez Martin <eperezma@...hat.com>
To: Jason Wang <jasowang@...hat.com>
Cc: mst@...hat.com, xuanzhuo@...ux.alibaba.com, virtualization@...ts.linux.dev, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 18/19] virtio_ring: factor out split indirect detaching logic

On Mon, Mar 24, 2025 at 7:02 AM Jason Wang <jasowang@...hat.com> wrote:
>
> Factor out the split indirect descriptor detaching logic in order to
> make it be reused by the in order support.
>

Acked-by: Eugenio Pérez <eperezma@...hat.com>

> Signed-off-by: Jason Wang <jasowang@...hat.com>
> ---
>  drivers/virtio/virtio_ring.c | 63 ++++++++++++++++++++----------------
>  1 file changed, 35 insertions(+), 28 deletions(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index a1a8cd931052..0fad8e8419c8 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -765,11 +765,42 @@ static bool virtqueue_kick_prepare_split(struct vring_virtqueue *vq)
>         return needs_kick;
>  }
>
> +static void detach_indirect_split(struct vring_virtqueue *vq,
> +                                 unsigned int head)
> +{
> +       struct vring_desc_extra *extra = vq->split.desc_extra;
> +       struct vring_desc *indir_desc =
> +              vq->split.desc_state[head].indir_desc;
> +       unsigned int j;
> +       u32 len, num;
> +
> +       /* Free the indirect table, if any, now that it's unmapped. */
> +       if (!indir_desc)
> +               return;
> +       len = vq->split.desc_extra[head].len;
> +
> +       BUG_ON(!(vq->split.desc_extra[head].flags &
> +                       VRING_DESC_F_INDIRECT));
> +       BUG_ON(len == 0 || len % sizeof(struct vring_desc));
> +
> +       num = len / sizeof(struct vring_desc);
> +
> +       extra = (struct vring_desc_extra *)&indir_desc[num];
> +
> +       if (vq->use_dma_api) {
> +               for (j = 0; j < num; j++)
> +                       vring_unmap_one_split(vq, &extra[j]);
> +       }
> +
> +       kfree(indir_desc);
> +       vq->split.desc_state[head].indir_desc = NULL;
> +}
> +
>  static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head,
>                              void **ctx)
>  {
>         struct vring_desc_extra *extra;
> -       unsigned int i, j;
> +       unsigned int i;
>         __virtio16 nextflag = cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT);
>
>         /* Clear data ptr. */
> @@ -793,34 +824,10 @@ static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head,
>         /* Plus final descriptor */
>         vq->vq.num_free++;
>
> -       if (vq->indirect) {
> -               struct vring_desc *indir_desc =
> -                               vq->split.desc_state[head].indir_desc;
> -               u32 len, num;
> -
> -               /* Free the indirect table, if any, now that it's unmapped. */
> -               if (!indir_desc)
> -                       return;
> -               len = vq->split.desc_extra[head].len;
> -
> -               BUG_ON(!(vq->split.desc_extra[head].flags &
> -                               VRING_DESC_F_INDIRECT));
> -               BUG_ON(len == 0 || len % sizeof(struct vring_desc));
> -
> -               num = len / sizeof(struct vring_desc);
> -
> -               extra = (struct vring_desc_extra *)&indir_desc[num];
> -
> -               if (vq->use_dma_api) {
> -                       for (j = 0; j < num; j++)
> -                               vring_unmap_one_split(vq, &extra[j]);
> -               }
> -
> -               kfree(indir_desc);
> -               vq->split.desc_state[head].indir_desc = NULL;
> -       } else if (ctx) {
> +       if (vq->indirect)
> +               detach_indirect_split(vq, head);
> +       else if (ctx)
>                 *ctx = vq->split.desc_state[head].indir_desc;
> -       }
>  }
>
>  static bool virtqueue_poll_split(const struct vring_virtqueue *vq,
> --
> 2.42.0
>