linux-kernel - Re: [PATCH 17/19] virtio_ring: move next_avail_idx to vring

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Message-ID: <CAJaqyWfzRDa5vn0nJiaPdy2=Qoi40jgUQbbAspm25zM7OfUyHg@mail.gmail.com>
Date: Wed, 26 Mar 2025 15:01:30 +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 17/19] virtio_ring: move next_avail_idx to vring_virtqueue

On Mon, Mar 24, 2025 at 7:01 AM Jason Wang <jasowang@...hat.com> wrote:
>
> This variable is used by packed virtqueue now, moving it to
> vring_virtqueue to make it possible to be reused by split virtqueue
> in-order implementation.
>

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

> Signed-off-by: Jason Wang <jasowang@...hat.com>
> ---
>  drivers/virtio/virtio_ring.c | 22 +++++++++++-----------
>  1 file changed, 11 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index bd4faf04862c..a1a8cd931052 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -138,9 +138,6 @@ struct vring_virtqueue_packed {
>         /* Avail used flags. */
>         u16 avail_used_flags;
>
> -       /* Index of the next avail descriptor. */
> -       u16 next_avail_idx;
> -
>         /*
>          * Last written value to driver->flags in
>          * guest byte order.
> @@ -214,6 +211,9 @@ struct vring_virtqueue {
>          */
>         u16 last_used_idx;
>
> +       /* Index of the next avail descriptor. */
> +       u16 next_avail_idx;
> +
>         /* Hint for event idx: already triggered no need to disable. */
>         bool event_triggered;
>
> @@ -448,6 +448,7 @@ static void virtqueue_init(struct vring_virtqueue *vq, u32 num)
>         else
>                 vq->last_used_idx = 0;
>
> +       vq->next_avail_idx = 0;
>         vq->event_triggered = false;
>         vq->num_added = 0;
>
> @@ -1350,7 +1351,7 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
>         u16 head, id;
>         dma_addr_t addr;
>
> -       head = vq->packed.next_avail_idx;
> +       head = vq->next_avail_idx;
>         desc = alloc_indirect_packed(total_sg, gfp);
>         if (!desc)
>                 return -ENOMEM;
> @@ -1431,7 +1432,7 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
>                                 1 << VRING_PACKED_DESC_F_AVAIL |
>                                 1 << VRING_PACKED_DESC_F_USED;
>         }
> -       vq->packed.next_avail_idx = n;
> +       vq->next_avail_idx = n;
>         vq->free_head = vq->packed.desc_extra[id].next;
>
>         /* Store token and indirect buffer state. */
> @@ -1501,7 +1502,7 @@ static inline int virtqueue_add_packed(struct vring_virtqueue *vq,
>                 /* fall back on direct */
>         }
>
> -       head = vq->packed.next_avail_idx;
> +       head = vq->next_avail_idx;
>         avail_used_flags = vq->packed.avail_used_flags;
>
>         WARN_ON_ONCE(total_sg > vq->packed.vring.num && !vq->indirect);
> @@ -1569,7 +1570,7 @@ static inline int virtqueue_add_packed(struct vring_virtqueue *vq,
>         vq->vq.num_free -= descs_used;
>
>         /* Update free pointer */
> -       vq->packed.next_avail_idx = i;
> +       vq->next_avail_idx = i;
>         vq->free_head = curr;
>
>         /* Store token. */
> @@ -1633,8 +1634,8 @@ static bool virtqueue_kick_prepare_packed(struct vring_virtqueue *vq)
>          */
>         virtio_mb(vq->weak_barriers);
>
> -       old = vq->packed.next_avail_idx - vq->num_added;
> -       new = vq->packed.next_avail_idx;
> +       old = vq->next_avail_idx - vq->num_added;
> +       new = vq->next_avail_idx;
>         vq->num_added = 0;
>
>         snapshot.u32 = *(u32 *)vq->packed.vring.device;
> @@ -2083,7 +2084,6 @@ static int vring_alloc_state_extra_packed(struct vring_virtqueue_packed *vring_p
>  static void virtqueue_vring_init_packed(struct vring_virtqueue_packed *vring_packed,
>                                         bool callback)
>  {
> -       vring_packed->next_avail_idx = 0;
>         vring_packed->avail_wrap_counter = 1;
>         vring_packed->event_flags_shadow = 0;
>         vring_packed->avail_used_flags = 1 << VRING_PACKED_DESC_F_AVAIL;
> @@ -2977,7 +2977,7 @@ u32 vring_notification_data(struct virtqueue *_vq)
>         u16 next;
>
>         if (vq->packed_ring)
> -               next = (vq->packed.next_avail_idx &
> +               next = (vq->next_avail_idx &
>                                 ~(-(1 << VRING_PACKED_EVENT_F_WRAP_CTR))) |
>                         vq->packed.avail_wrap_counter <<
>                                 VRING_PACKED_EVENT_F_WRAP_CTR;
> --
> 2.42.0
>