On Tue, 7 Mar 2023 14:43:35 +0800, Jason Wang <jasowang@xxxxxxxxxx> wrote:
> On Thu, Mar 2, 2023 at 7:59 PM Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx> wrote:
> >
> > This commit splits virtqueue_add_split() to two functions. The purpose
> > of such splitting is to separate DMA operations.
> >
> > The first function includes all codes that may fail before the DMA
> > operation. The subsequent part is used as the second function.
> >
> > In this way, we can perform DMA operations in the middle of the two
> > functions. If the first function fails, we do not need to perform DMA
> > operations. If it is premapped, we can pass the DMA operation.
> >
> > Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
> > ---
> > drivers/virtio/virtio_ring.c | 131 +++++++++++++++++++++++------------
> > 1 file changed, 88 insertions(+), 43 deletions(-)
> >
> > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> > index 41144b5246a8..3005893ecc61 100644
> > --- a/drivers/virtio/virtio_ring.c
> > +++ b/drivers/virtio/virtio_ring.c
> > @@ -520,57 +520,38 @@ 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)
> > +/* note: return NULL means no indirect that is valid. */
> > +static struct vring_desc *virtqueue_get_desc_split(struct vring_virtqueue *vq,
> > + unsigned int total_sg,
> > + unsigned int out_sgs,
> > + void *data,
> > + void *ctx,
> > + gfp_t gfp)
> > {
>
> I don't object to the changes but I don't see much value in factoring
> this out, since it's not related to any dma mapping logic.
I want:
virtqueue_get_desc_split()
---> virtqueue_map_sgs()
virtqueue_add_vring_split()
Then we can choose to do dma or not without flags to virtqueue_add_vring_split().
So I split the virtqueue_add_split() to two funcs.
>
> > - 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;
> > -
> > - START_USE(vq);
> > + unsigned int descs_used;
> >
> > BUG_ON(data == NULL);
> > BUG_ON(ctx && vq->indirect);
> >
> > - if (unlikely(vq->broken)) {
> > - END_USE(vq);
> > - return -EIO;
> > - }
> > + if (unlikely(vq->broken))
> > + return ERR_PTR(-EIO);
> >
> > LAST_ADD_TIME_UPDATE(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",
> > @@ -580,10 +561,39 @@ 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);
> > - return -ENOSPC;
> > + kfree(desc);
> > + return ERR_PTR(-ENOSPC);
> > + }
> > +
> > + return desc;
> > +}
> > +
> > +static inline int virtqueue_add_vring_split(struct vring_virtqueue *vq,
> > + struct scatterlist *sgs[],
> > + unsigned int total_sg,
> > + unsigned int out_sgs,
> > + unsigned int in_sgs,
> > + struct vring_desc *desc)
> > +{
> > + struct virtqueue *_vq = &vq->vq;
> > + struct scatterlist *sg;
> > + unsigned int i, n, avail, descs_used, prev, err_idx;
> > + int head;
> > + bool indirect;
> > +
> > + 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++) {
> > @@ -648,13 +658,6 @@ 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);
> > @@ -703,6 +706,48 @@ static inline int virtqueue_add_split(struct virtqueue *_vq,
> > return -ENOMEM;
> > }
> >
> > +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;
> > +
> > + START_USE(vq);
> > +
> > + /* check vq state and try to alloc desc for indirect. */
> > + desc = virtqueue_get_desc_split(vq, total_sg, out_sgs, data, ctx, gfp);
> > + if (IS_ERR(desc)) {
> > + err = PTR_ERR(desc);
> > + goto end;
> > + }
> > +
> > + head = vq->free_head;
> > + err = virtqueue_add_vring_split(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;
>
> Nit: this seems not elegant. I would rather duplicate
>
> END_USE(vq);
> return err;
>
Will fix.
Thanks.
> here.
>
> Thanks
>
>
>
>
> > +
> > +err:
> > + kfree(desc);
> > +
> > +end:
> > + END_USE(vq);
> > + return err;
> > +}
> > +
> > static bool virtqueue_kick_prepare_split(struct virtqueue *_vq)
> > {
> > struct vring_virtqueue *vq = to_vvq(_vq);
> > --
> > 2.32.0.3.g01195cf9f
> >
>
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