netdev - Re: [PATCH vhost v10 04/10] virtio_ring: packed: support add premapped buf

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Date: Tue, 27 Jun 2023 16:03:29 +0800
From: Jason Wang <jasowang@...hat.com>
To: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Cc: virtualization@...ts.linux-foundation.org, 
	"Michael S. Tsirkin" <mst@...hat.com>, "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, Jesper Dangaard Brouer <hawk@...nel.org>, 
	John Fastabend <john.fastabend@...il.com>, netdev@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH vhost v10 04/10] virtio_ring: packed: support add
 premapped buf

On Fri, Jun 2, 2023 at 5:22 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
>
> If the vq is the premapped mode, use the sg_dma_address() directly.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> ---
>  drivers/virtio/virtio_ring.c | 36 ++++++++++++++++++++++++++----------
>  1 file changed, 26 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 18212c3e056b..dc109fbc05a5 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -1299,9 +1299,13 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
>
>         for (n = 0; n < out_sgs + in_sgs; n++) {
>                 for (sg = sgs[n]; sg; sg = sg_next(sg)) {
> -                       if (vring_map_one_sg(vq, sg, n < out_sgs ?
> -                                            DMA_TO_DEVICE : DMA_FROM_DEVICE, &addr))
> -                               goto unmap_release;
> +                       if (vq->premapped) {
> +                               addr = sg_dma_address(sg);
> +                       } else {
> +                               if (vring_map_one_sg(vq, sg, n < out_sgs ?
> +                                                    DMA_TO_DEVICE : DMA_FROM_DEVICE, &addr))
> +                                       goto unmap_release;
> +                       }
>
>                         desc[i].flags = cpu_to_le16(n < out_sgs ?
>                                                 0 : VRING_DESC_F_WRITE);
> @@ -1369,10 +1373,12 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
>         return 0;
>
>  unmap_release:
> -       err_idx = i;
> +       if (!vq->premapped) {
> +               err_idx = i;
>
> -       for (i = 0; i < err_idx; i++)
> -               vring_unmap_desc_packed(vq, &desc[i]);
> +               for (i = 0; i < err_idx; i++)
> +                       vring_unmap_desc_packed(vq, &desc[i]);
> +       }
>
>         kfree(desc);
>
> @@ -1447,9 +1453,13 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
>                 for (sg = sgs[n]; sg; sg = sg_next(sg)) {
>                         dma_addr_t addr;
>
> -                       if (vring_map_one_sg(vq, sg, n < out_sgs ?
> -                                            DMA_TO_DEVICE : DMA_FROM_DEVICE, &addr))
> -                               goto unmap_release;
> +                       if (vq->premapped) {
> +                               addr = sg_dma_address(sg);
> +                       } else {
> +                               if (vring_map_one_sg(vq, sg, n < out_sgs ?
> +                                                    DMA_TO_DEVICE : DMA_FROM_DEVICE, &addr))
> +                                       goto unmap_release;
> +                       }
>
>                         flags = cpu_to_le16(vq->packed.avail_used_flags |
>                                     (++c == total_sg ? 0 : VRING_DESC_F_NEXT) |
> @@ -1512,11 +1522,17 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
>         return 0;
>
>  unmap_release:
> +       vq->packed.avail_used_flags = avail_used_flags;
> +
> +       if (vq->premapped) {

Similar to the split path, I think we can't hit vq->premapped here.

Thanks


> +               END_USE(vq);
> +               return -EIO;
> +       }
> +
>         err_idx = i;
>         i = head;
>         curr = vq->free_head;
>
> -       vq->packed.avail_used_flags = avail_used_flags;
>
>         for (n = 0; n < total_sg; n++) {
>                 if (i == err_idx)
> --
> 2.32.0.3.g01195cf9f
>