On Mon, Feb 20, 2023 at 01:37:37PM +0800, Jason Wang wrote:
> On Tue, Feb 14, 2023 at 3:27 PM Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx> wrote:
> >
> > DMA-related logic is separated from the virtqueue_add_split to prepare
> > for subsequent support for premapped.
>
> The patch seems to do more than what is described here.
>
> To simplify reviewers, I'd suggest to split this patch into three:
>
> 1) virtqueue_add_split_prepare() (could we have a better name?)
> 2) virtqueue_map_sgs()
> 3) virtqueue_add_split_vring()
>
> (Or only factor DMA parts out, I haven't gone through the reset of the patches)
>
> Thanks
>
It's pretty small, even split is not mandatary imho.
But definitely please do document what is done fully.
> >
> > Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
> > ---
> > drivers/virtio/virtio_ring.c | 219 ++++++++++++++++++++++++-----------
> > 1 file changed, 152 insertions(+), 67 deletions(-)
> >
> > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> > index 41144b5246a8..560ee30d942c 100644
> > --- a/drivers/virtio/virtio_ring.c
> > +++ b/drivers/virtio/virtio_ring.c
> > @@ -520,29 +520,83 @@ static inline unsigned int virtqueue_add_desc_split(struct virtqueue *vq,
> > return next;
> > }
> >
> > -static inline int virtqueue_add_split(struct virtqueue *_vq,
> > - struct scatterlist *sgs[],
> > - unsigned int total_sg,
> > - unsigned int out_sgs,
> > - unsigned int in_sgs,
> > - void *data,
> > - void *ctx,
> > - gfp_t gfp)
> > +static int virtqueue_map_sgs(struct vring_virtqueue *vq,
> > + struct scatterlist *sgs[],
> > + unsigned int total_sg,
> > + unsigned int out_sgs,
> > + unsigned int in_sgs)
> > {
> > - struct vring_virtqueue *vq = to_vvq(_vq);
> > struct scatterlist *sg;
> > - struct vring_desc *desc;
> > - unsigned int i, n, avail, descs_used, prev, err_idx;
> > - int head;
> > - bool indirect;
> > + unsigned int n;
> >
> > - START_USE(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))
> > + return -ENOMEM;
> > +
> > + sg->dma_address = addr;
> > + }
> > + }
> > + 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))
> > + return -ENOMEM;
> > +
> > + sg->dma_address = addr;
> > + }
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +static void virtqueue_unmap_sgs(struct vring_virtqueue *vq,
> > + struct scatterlist *sgs[],
> > + unsigned int total_sg,
> > + unsigned int out_sgs,
> > + unsigned int in_sgs)
> > +{
> > + struct scatterlist *sg;
> > + unsigned int n;
> > +
> > + for (n = 0; n < out_sgs; n++) {
> > + for (sg = sgs[n]; sg; sg = sg_next(sg)) {
> > + if (!sg->dma_address)
> > + return;
> > +
> > + dma_unmap_single(vring_dma_dev(vq), sg->dma_address,
> > + sg->length, DMA_TO_DEVICE);
> > + }
> > + }
> > + for (; n < (out_sgs + in_sgs); n++) {
> > + for (sg = sgs[n]; sg; sg = sg_next(sg)) {
> > + if (!sg->dma_address)
> > + return;
> > +
> > + dma_unmap_single(vring_dma_dev(vq), sg->dma_address,
> > + sg->length, DMA_FROM_DEVICE);
> > + }
> > + }
> > +}
> > +
> > +static inline int virtqueue_add_split_prepare(struct vring_virtqueue *vq,
> > + unsigned int total_sg,
> > + unsigned int out_sgs,
> > + void *data,
> > + void *ctx,
> > + gfp_t gfp,
> > + struct vring_desc **pdesc)
> > +{
> > + struct vring_desc *desc;
> > + unsigned int descs_used;
> >
> > BUG_ON(data == NULL);
> > BUG_ON(ctx && vq->indirect);
> >
> > if (unlikely(vq->broken)) {
> > - END_USE(vq);
> > return -EIO;
> > }
> >
> > @@ -550,27 +604,17 @@ static inline int virtqueue_add_split(struct virtqueue *_vq,
> >
> > BUG_ON(total_sg == 0);
> >
> > - head = vq->free_head;
> > -
> > if (virtqueue_use_indirect(vq, total_sg))
> > - desc = alloc_indirect_split(_vq, total_sg, gfp);
> > + desc = alloc_indirect_split(&vq->vq, total_sg, gfp);
> > else {
> > desc = NULL;
> > WARN_ON_ONCE(total_sg > vq->split.vring.num && !vq->indirect);
> > }
> >
> > - if (desc) {
> > - /* Use a single buffer which doesn't continue */
> > - indirect = true;
> > - /* Set up rest to use this indirect table. */
> > - i = 0;
> > + if (desc)
> > descs_used = 1;
> > - } else {
> > - indirect = false;
> > - desc = vq->split.vring.desc;
> > - i = head;
> > + else
> > descs_used = total_sg;
> > - }
> >
> > if (unlikely(vq->vq.num_free < descs_used)) {
> > pr_debug("Can't add buf len %i - avail = %i\n",
> > @@ -580,38 +624,64 @@ static inline int virtqueue_add_split(struct virtqueue *_vq,
> > * host should service the ring ASAP. */
> > if (out_sgs)
> > vq->notify(&vq->vq);
> > - if (indirect)
> > - kfree(desc);
> > - END_USE(vq);
> > + kfree(desc);
> > return -ENOSPC;
> > }
> >
> > + *pdesc = desc;
> > +
> > + return 0;
> > +}
> > +
> > +static inline int virtqueue_add_split_vring(struct vring_virtqueue *vq,
> > + struct scatterlist *sgs[],
> > + unsigned int total_sg,
> > + unsigned int out_sgs,
> > + unsigned int in_sgs,
> > + struct vring_desc *desc)
> > +{
> > + unsigned int n, i, avail, descs_used, prev;
> > + struct virtqueue *_vq = &vq->vq;
> > + struct scatterlist *sg;
> > + bool indirect;
> > + int head;
> > +
> > + head = vq->free_head;
> > +
> > + if (desc) {
> > + /* Use a single buffer which doesn't continue */
> > + indirect = true;
> > + /* Set up rest to use this indirect table. */
> > + i = 0;
> > + descs_used = 1;
> > + } else {
> > + indirect = false;
> > + desc = vq->split.vring.desc;
> > + i = head;
> > + descs_used = total_sg;
> > + }
> > +
> > 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))
> > - goto unmap_release;
> > -
> > prev = i;
> > /* Note that we trust indirect descriptor
> > * table since it use stream DMA mapping.
> > */
> > - i = virtqueue_add_desc_split(_vq, desc, i, addr, sg->length,
> > + i = virtqueue_add_desc_split(_vq, desc, i,
> > + sg->dma_address,
> > + sg->length,
> > VRING_DESC_F_NEXT,
> > indirect);
> > }
> > }
> > 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))
> > - goto unmap_release;
> > -
> > prev = i;
> > /* Note that we trust indirect descriptor
> > * table since it use stream DMA mapping.
> > */
> > - i = virtqueue_add_desc_split(_vq, desc, i, addr,
> > + i = virtqueue_add_desc_split(_vq, desc, i,
> > + sg->dma_address,
> > sg->length,
> > VRING_DESC_F_NEXT |
> > VRING_DESC_F_WRITE,
> > @@ -630,7 +700,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq,
> > vq, desc, total_sg * sizeof(struct vring_desc),
> > DMA_TO_DEVICE);
> > if (vring_mapping_error(vq, addr))
> > - goto unmap_release;
> > + return -ENOMEM;
> >
> > virtqueue_add_desc_split(_vq, vq->split.vring.desc,
> > head, addr,
> > @@ -648,13 +718,6 @@ static inline int virtqueue_add_split(struct virtqueue *_vq,
> > else
> > vq->free_head = i;
> >
> > - /* Store token and indirect buffer state. */
> > - vq->split.desc_state[head].data = data;
> > - if (indirect)
> > - vq->split.desc_state[head].indir_desc = desc;
> > - else
> > - vq->split.desc_state[head].indir_desc = ctx;
> > -
> > /* Put entry in available array (but don't update avail->idx until they
> > * do sync). */
> > avail = vq->split.avail_idx_shadow & (vq->split.vring.num - 1);
> > @@ -677,30 +740,52 @@ static inline int virtqueue_add_split(struct virtqueue *_vq,
> > virtqueue_kick(_vq);
> >
> > return 0;
> > +}
> >
> > -unmap_release:
> > - err_idx = i;
> > +static inline int virtqueue_add_split(struct virtqueue *_vq,
> > + struct scatterlist *sgs[],
> > + unsigned int total_sg,
> > + unsigned int out_sgs,
> > + unsigned int in_sgs,
> > + void *data,
> > + void *ctx,
> > + gfp_t gfp)
> > +{
> > + struct vring_virtqueue *vq = to_vvq(_vq);
> > + struct vring_desc *desc;
> > + int head;
> > + int err;
> >
> > - if (indirect)
> > - i = 0;
> > - else
> > - i = head;
> > + START_USE(vq);
> >
> > - for (n = 0; n < total_sg; n++) {
> > - if (i == err_idx)
> > - break;
> > - if (indirect) {
> > - vring_unmap_one_split_indirect(vq, &desc[i]);
> > - i = virtio16_to_cpu(_vq->vdev, desc[i].next);
> > - } else
> > - i = vring_unmap_one_split(vq, i);
> > - }
> > + /* check vq state and try to alloc desc for indirect. */
> > + err = virtqueue_add_split_prepare(vq, total_sg, out_sgs, data, ctx, gfp, &desc);
> > + if (err)
> > + goto end;
> >
> > - if (indirect)
> > - kfree(desc);
> > + err = virtqueue_map_sgs(vq, sgs, total_sg, out_sgs, in_sgs);
> > + if (err)
> > + goto err;
> >
> > + head = vq->free_head;
> > + err = virtqueue_add_split_vring(vq, sgs, total_sg, out_sgs, in_sgs, desc);
> > + if (err)
> > + goto err;
> > +
> > + /* Store token and indirect buffer state. */
> > + vq->split.desc_state[head].data = data;
> > + vq->split.desc_state[head].indir_desc = desc ? desc : ctx;
> > +
> > + goto end;
> > +
> > +err:
> > + virtqueue_unmap_sgs(vq, sgs, total_sg, out_sgs, in_sgs);
> > +
> > + kfree(desc);
> > +
> > +end:
> > END_USE(vq);
> > - return -ENOMEM;
> > + return err;
> > }
> >
> > static bool virtqueue_kick_prepare_split(struct virtqueue *_vq)
> > --
> > 2.32.0.3.g01195cf9f
> >
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