On Tue, Mar 21, 2023 at 05:34:59PM +0800, Xuan Zhuo wrote:
> virtio core only supports virtual addresses, dma is completed in virtio
> core.
>
> In some scenarios (such as the AF_XDP), the memory is allocated
> and DMA mapping is completed in advance, so it is necessary for us to
> support passing the DMA address to virtio core.
>
> Drives can use sg->dma_address to pass the mapped dma address to virtio
> core. If one sg->dma_address is used then all sgs must use
> sg->dma_address, otherwise all must be null when passing it to the APIs
> of virtio.
>
> Signed-off-by: Xuan Zhuo <[email protected]>
> ---
> drivers/virtio/virtio_ring.c | 27 +++++++++++++++++++--------
> 1 file changed, 19 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index c8ed4aef9462..be2ff96964c3 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -70,6 +70,7 @@
> struct vring_desc_state_split {
> void *data; /* Data for callback. */
> struct vring_desc *indir_desc; /* Indirect descriptor, if any. */
> + bool map_inter; /* Do dma map internally. */
I prefer a full name. E.g. "dma_map_internal". Eschew abbreviation.
> };
>
> struct vring_desc_state_packed {
> @@ -448,7 +449,7 @@ static void vring_unmap_one_split_indirect(const struct
> vring_virtqueue *vq,
> }
>
> static unsigned int vring_unmap_one_split(const struct vring_virtqueue *vq,
> - unsigned int i)
> + unsigned int i, bool map_inter)
> {
> struct vring_desc_extra *extra = vq->split.desc_extra;
> u16 flags;
> @@ -465,6 +466,9 @@ static unsigned int vring_unmap_one_split(const struct
> vring_virtqueue *vq,
> (flags & VRING_DESC_F_WRITE) ?
> DMA_FROM_DEVICE : DMA_TO_DEVICE);
> } else {
> + if (!map_inter)
> + goto out;
> +
> dma_unmap_page(vring_dma_dev(vq),
> extra[i].addr,
> extra[i].len,
> @@ -615,7 +619,7 @@ static inline int virtqueue_add_split(struct virtqueue
> *_vq,
> struct scatterlist *sg;
> struct vring_desc *desc;
> unsigned int i, n, avail, descs_used, prev;
> - bool indirect;
> + bool indirect, map_inter;
> int head;
>
> START_USE(vq);
> @@ -668,7 +672,8 @@ static inline int virtqueue_add_split(struct virtqueue
> *_vq,
> return -ENOSPC;
> }
>
> - if (virtqueue_map_sgs(vq, sgs, total_sg, out_sgs, in_sgs))
> + map_inter = !sgs[0]->dma_address;
> + if (map_inter && virtqueue_map_sgs(vq, sgs, total_sg, out_sgs, in_sgs))
> return -ENOMEM;
>
> for (n = 0; n < out_sgs; n++) {
> @@ -734,6 +739,7 @@ static inline int virtqueue_add_split(struct virtqueue
> *_vq,
> vq->split.desc_state[head].indir_desc = desc;
> else
> vq->split.desc_state[head].indir_desc = ctx;
> + vq->split.desc_state[head].map_inter = map_inter;
>
> /* Put entry in available array (but don't update avail->idx until they
> * do sync). */
> @@ -759,7 +765,8 @@ static inline int virtqueue_add_split(struct virtqueue
> *_vq,
> return 0;
>
> unmap_release:
> - virtqueue_unmap_sgs(vq, sgs, total_sg, out_sgs, in_sgs);
> + if (map_inter)
> + virtqueue_unmap_sgs(vq, sgs, total_sg, out_sgs, in_sgs);
>
> if (indirect)
> kfree(desc);
> @@ -804,20 +811,22 @@ static void detach_buf_split(struct vring_virtqueue
> *vq, unsigned int head,
> {
> unsigned int i, j;
> __virtio16 nextflag = cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT);
> + bool map_inter;
>
> /* Clear data ptr. */
> vq->split.desc_state[head].data = NULL;
> + map_inter = vq->split.desc_state[head].map_inter;
>
> /* Put back on free list: unmap first-level descriptors and find end */
> i = head;
>
> while (vq->split.vring.desc[i].flags & nextflag) {
> - vring_unmap_one_split(vq, i);
> + vring_unmap_one_split(vq, i, map_inter);
> i = vq->split.desc_extra[i].next;
> vq->vq.num_free++;
> }
>
> - vring_unmap_one_split(vq, i);
> + vring_unmap_one_split(vq, i, map_inter);
> vq->split.desc_extra[i].next = vq->free_head;
> vq->free_head = head;
>
> @@ -839,8 +848,10 @@ static void detach_buf_split(struct vring_virtqueue *vq,
> unsigned int head,
> VRING_DESC_F_INDIRECT));
> BUG_ON(len == 0 || len % sizeof(struct vring_desc));
>
> - for (j = 0; j < len / sizeof(struct vring_desc); j++)
> - vring_unmap_one_split_indirect(vq, &indir_desc[j]);
> + if (map_inter) {
> + for (j = 0; j < len / sizeof(struct vring_desc); j++)
> + vring_unmap_one_split_indirect(vq,
> &indir_desc[j]);
> + }
>
> kfree(indir_desc);
> vq->split.desc_state[head].indir_desc = NULL;
> --
> 2.32.0.3.g01195cf9f
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