Re: [PATCH vhost v10 01/10] virtio_ring: put mapping error check in vring_map_one_sg

From: Jason Wang <jasowang@redhat.com>
To: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Cc: virtualization@lists.linux-foundation.org,
	 "Michael S. Tsirkin" <mst@redhat.com>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	 Jakub Kicinski <kuba@kernel.org>,
	Paolo Abeni <pabeni@redhat.com>,
	Alexei Starovoitov <ast@kernel.org>,
	 Daniel Borkmann <daniel@iogearbox.net>,
	Jesper Dangaard Brouer <hawk@kernel.org>,
	 John Fastabend <john.fastabend@gmail.com>,
	netdev@vger.kernel.org, bpf@vger.kernel.org
Subject: Re: [PATCH vhost v10 01/10] virtio_ring: put mapping error check in vring_map_one_sg
Date: Tue, 27 Jun 2023 16:03:19 +0800	[thread overview]
Message-ID: <CACGkMEuS3DsjgP0RB2C-DbsACq4FU6RKD4C+p3dOGQHWdZJJhg@mail.gmail.com> (raw)
In-Reply-To: <20230602092206.50108-2-xuanzhuo@linux.alibaba.com>

On Fri, Jun 2, 2023 at 5:22 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote:
>
> This patch put the dma addr error check in vring_map_one_sg().
>
> The benefits of doing this:
>
> 1. reduce one judgment of vq->use_dma_api.
> 2. make vring_map_one_sg more simple, without calling
>    vring_mapping_error to check the return value. simplifies subsequent
>    code
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>

Acked-by: Jason Wang <jasowang@redhat.com>

Thanks


> ---
>  drivers/virtio/virtio_ring.c | 37 +++++++++++++++++++++---------------
>  1 file changed, 22 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index c5310eaf8b46..72ed07a604d4 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -355,9 +355,8 @@ static struct device *vring_dma_dev(const struct vring_virtqueue *vq)
>  }
>
>  /* Map one sg entry. */
> -static dma_addr_t vring_map_one_sg(const struct vring_virtqueue *vq,
> -                                  struct scatterlist *sg,
> -                                  enum dma_data_direction direction)
> +static int vring_map_one_sg(const struct vring_virtqueue *vq, struct scatterlist *sg,
> +                           enum dma_data_direction direction, dma_addr_t *addr)
>  {
>         if (!vq->use_dma_api) {
>                 /*
> @@ -366,7 +365,8 @@ static dma_addr_t vring_map_one_sg(const struct vring_virtqueue *vq,
>                  * depending on the direction.
>                  */
>                 kmsan_handle_dma(sg_page(sg), sg->offset, sg->length, direction);
> -               return (dma_addr_t)sg_phys(sg);
> +               *addr = (dma_addr_t)sg_phys(sg);
> +               return 0;
>         }
>
>         /*
> @@ -374,9 +374,14 @@ static dma_addr_t vring_map_one_sg(const struct vring_virtqueue *vq,
>          * the way it expects (we don't guarantee that the scatterlist
>          * will exist for the lifetime of the mapping).
>          */
> -       return dma_map_page(vring_dma_dev(vq),
> +       *addr = dma_map_page(vring_dma_dev(vq),
>                             sg_page(sg), sg->offset, sg->length,
>                             direction);
> +
> +       if (dma_mapping_error(vring_dma_dev(vq), *addr))
> +               return -ENOMEM;
> +
> +       return 0;
>  }
>
>  static dma_addr_t vring_map_single(const struct vring_virtqueue *vq,
> @@ -588,8 +593,9 @@ static inline int virtqueue_add_split(struct virtqueue *_vq,
>
>         for (n = 0; n < out_sgs; n++) {
>                 for (sg = sgs[n]; sg; sg = sg_next(sg)) {
> -                       dma_addr_t addr = vring_map_one_sg(vq, sg, DMA_TO_DEVICE);
> -                       if (vring_mapping_error(vq, addr))
> +                       dma_addr_t addr;
> +
> +                       if (vring_map_one_sg(vq, sg, DMA_TO_DEVICE, &addr))
>                                 goto unmap_release;
>
>                         prev = i;
> @@ -603,8 +609,9 @@ static inline int virtqueue_add_split(struct virtqueue *_vq,
>         }
>         for (; n < (out_sgs + in_sgs); n++) {
>                 for (sg = sgs[n]; sg; sg = sg_next(sg)) {
> -                       dma_addr_t addr = vring_map_one_sg(vq, sg, DMA_FROM_DEVICE);
> -                       if (vring_mapping_error(vq, addr))
> +                       dma_addr_t addr;
> +
> +                       if (vring_map_one_sg(vq, sg, DMA_FROM_DEVICE, &addr))
>                                 goto unmap_release;
>
>                         prev = i;
> @@ -1279,9 +1286,8 @@ 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)) {
> -                       addr = vring_map_one_sg(vq, sg, n < out_sgs ?
> -                                       DMA_TO_DEVICE : DMA_FROM_DEVICE);
> -                       if (vring_mapping_error(vq, addr))
> +                       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 ?
> @@ -1426,9 +1432,10 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
>         c = 0;
>         for (n = 0; n < out_sgs + in_sgs; n++) {
>                 for (sg = sgs[n]; sg; sg = sg_next(sg)) {
> -                       dma_addr_t addr = vring_map_one_sg(vq, sg, n < out_sgs ?
> -                                       DMA_TO_DEVICE : DMA_FROM_DEVICE);
> -                       if (vring_mapping_error(vq, addr))
> +                       dma_addr_t addr;
> +
> +                       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 |
> --
> 2.32.0.3.g01195cf9f
>