On Wed, 31 Jan 2024 17:12:19 +0800, Jason Wang <jasowang@xxxxxxxxxx> wrote: > On Tue, Jan 30, 2024 at 7:42 PM Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx> wrote: > > > > In the functions vring_unmap_extra_packed and vring_unmap_desc_packed, > > multiple checks are made whether unmap is performed and whether it is > > INDIRECT. > > > > These two functions are usually called in a loop, and we should put the > > check outside the loop. > > > > And we unmap the descs with VRING_DESC_F_INDIRECT on the same path with > > other descs, that make the thing more complex. If we distinguish the > > descs with VRING_DESC_F_INDIRECT before unmap, thing will be clearer. > > > > 1. only one desc of the desc table is used, we do not need the loop > > 2. the called unmap api is difference from the other desc > > 3. the vq->premapped is not needed to check > > 4. the vq->indirect is not needed to check > > 5. the state->indir_desc must not be null > > > > Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx> > > --- > > drivers/virtio/virtio_ring.c | 76 ++++++++++++++++++------------------ > > 1 file changed, 39 insertions(+), 37 deletions(-) > > > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > > index 4677831e6c26..7280a1706cca 100644 > > --- a/drivers/virtio/virtio_ring.c > > +++ b/drivers/virtio/virtio_ring.c > > @@ -1220,6 +1220,7 @@ static u16 packed_last_used(u16 last_used_idx) > > return last_used_idx & ~(-(1 << VRING_PACKED_EVENT_F_WRAP_CTR)); > > } > > > > +/* caller must check vring_need_unmap_buffer() */ > > static void vring_unmap_extra_packed(const struct vring_virtqueue *vq, > > const struct vring_desc_extra *extra) > > { > > @@ -1227,33 +1228,18 @@ static void vring_unmap_extra_packed(const struct vring_virtqueue *vq, > > > > flags = extra->flags; > > > > - if (flags & VRING_DESC_F_INDIRECT) { > > - if (!vq->use_dma_api) > > - return; > > - > > - dma_unmap_single(vring_dma_dev(vq), > > - extra->addr, extra->len, > > - (flags & VRING_DESC_F_WRITE) ? > > - DMA_FROM_DEVICE : DMA_TO_DEVICE); > > - } else { > > - if (!vring_need_unmap_buffer(vq)) > > - return; > > - > > - dma_unmap_page(vring_dma_dev(vq), > > - extra->addr, extra->len, > > - (flags & VRING_DESC_F_WRITE) ? > > - DMA_FROM_DEVICE : DMA_TO_DEVICE); > > - } > > + dma_unmap_page(vring_dma_dev(vq), > > + extra->addr, extra->len, > > + (flags & VRING_DESC_F_WRITE) ? > > + DMA_FROM_DEVICE : DMA_TO_DEVICE); > > } > > > > +/* caller must check vring_need_unmap_buffer() */ > > static void vring_unmap_desc_packed(const struct vring_virtqueue *vq, > > const struct vring_packed_desc *desc) > > { > > u16 flags; > > > > - if (!vring_need_unmap_buffer(vq)) > > - return; > > - > > flags = le16_to_cpu(desc->flags); > > > > dma_unmap_page(vring_dma_dev(vq), > > @@ -1329,7 +1315,7 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq, > > total_sg * sizeof(struct vring_packed_desc), > > DMA_TO_DEVICE); > > if (vring_mapping_error(vq, addr)) { > > - if (vq->premapped) > > + if (!vring_need_unmap_buffer(vq)) > > goto free_desc; > > > > goto unmap_release; > > @@ -1344,10 +1330,11 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq, > > vq->packed.desc_extra[id].addr = addr; > > vq->packed.desc_extra[id].len = total_sg * > > sizeof(struct vring_packed_desc); > > - vq->packed.desc_extra[id].flags = VRING_DESC_F_INDIRECT | > > - vq->packed.avail_used_flags; > > } > > > > + vq->packed.desc_extra[id].flags = VRING_DESC_F_INDIRECT | > > + vq->packed.avail_used_flags; > > Is this a bug fix? Or if we only need to check _F_INDIRECT, we can > simply avoid doing this by checking vq->indirect && state->indir_desc? > > > + > > /* > > * A driver MUST NOT make the first descriptor in the list > > * available before all subsequent descriptors comprising > > @@ -1388,6 +1375,8 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq, > > unmap_release: > > err_idx = i; > > > > + WARN_ON(!vring_need_unmap_buffer(vq)); > > Nitpick, using BUG_ON might be better as it may lead to unexpected > results which we can't recover from. the checkpatch.pl does not like BUG_ON. I have not preference. > > > + > > for (i = 0; i < err_idx; i++) > > vring_unmap_desc_packed(vq, &desc[i]); > > > > @@ -1484,9 +1473,10 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq, > > if (unlikely(vring_need_unmap_buffer(vq))) { > > vq->packed.desc_extra[curr].addr = addr; > > vq->packed.desc_extra[curr].len = sg->length; > > - vq->packed.desc_extra[curr].flags = > > - le16_to_cpu(flags); > > } > > + > > + vq->packed.desc_extra[curr].flags = le16_to_cpu(flags); > > + > > prev = curr; > > curr = vq->packed.desc_extra[curr].next; > > > > @@ -1536,6 +1526,8 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq, > > > > vq->packed.avail_used_flags = avail_used_flags; > > > > + WARN_ON(!vring_need_unmap_buffer(vq)); > > + > > for (n = 0; n < total_sg; n++) { > > if (i == err_idx) > > break; > > @@ -1605,7 +1597,9 @@ static void detach_buf_packed(struct vring_virtqueue *vq, > > struct vring_desc_state_packed *state = NULL; > > struct vring_packed_desc *desc; > > unsigned int i, curr; > > + u16 flags; > > > > + flags = vq->packed.desc_extra[id].flags; > > state = &vq->packed.desc_state[id]; > > > > /* Clear data ptr. */ > > @@ -1615,22 +1609,32 @@ static void detach_buf_packed(struct vring_virtqueue *vq, > > vq->free_head = id; > > vq->vq.num_free += state->num; > > > > - if (unlikely(vring_need_unmap_buffer(vq))) { > > - curr = id; > > - for (i = 0; i < state->num; i++) { > > - vring_unmap_extra_packed(vq, > > - &vq->packed.desc_extra[curr]); > > - curr = vq->packed.desc_extra[curr].next; > > + if (!(flags & VRING_DESC_F_INDIRECT)) { > > + if (vring_need_unmap_buffer(vq)) { > > + curr = id; > > + for (i = 0; i < state->num; i++) { > > + vring_unmap_extra_packed(vq, > > + &vq->packed.desc_extra[curr]); > > + curr = vq->packed.desc_extra[curr].next; > > + } > > So before the change, we had: > > if (unlikely(vq->do_unmap)) { > curr = id; > for (i = 0; i < state->num; i++) { > vring_unmap_extra_packed(vq, > &vq->packed.desc_extra[curr]); > curr = vq->packed.desc_extra[curr].next; > } > } > > This looks like a bug as we should unmap the indirect descriptor > regradless of whether do_unmap is true or false. > > If yes, we need a independent fix instead of squashing it in this patch? YES. I noticed this. I will post a fix to the stable branch. Thanks. > > > } > > - } > > > > - if (vq->indirect) { > > + if (ctx) > > + *ctx = state->indir_desc; > > + } else { > > + const struct vring_desc_extra *extra; > > u32 len; > > > > + if (vq->use_dma_api) { > > + extra = &vq->packed.desc_extra[id]; > > + dma_unmap_single(vring_dma_dev(vq), > > + extra->addr, extra->len, > > + (flags & VRING_DESC_F_WRITE) ? > > + DMA_FROM_DEVICE : DMA_TO_DEVICE); > > + } > > + > > Thanks >