Re: [RFC v2 5/7] virtio: unmask F_NEXT flag in desc_extra

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在 2022/8/17 21:57, Guo Zhi 写道:
We didn't unmask F_NEXT flag in desc_extra in the end of a chain,
unmask it so that we can access desc_extra to get next information.

Signed-off-by: Guo Zhi <qtxuning1999@xxxxxxxxxxx>


I post a similar patch in the past.

Please share the perf numbers (e.g pps via pktgen).

Thanks


---
  drivers/virtio/virtio_ring.c | 6 ++++--
  1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index a5ec724c01d8..1c1b3fa376a2 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -567,7 +567,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq,
  	}
  	/* Last one doesn't continue. */
  	desc[prev].flags &= cpu_to_virtio16(_vq->vdev, ~VRING_DESC_F_NEXT);
-	if (!indirect && vq->use_dma_api)
+	if (!indirect)
  		vq->split.desc_extra[prev & (vq->split.vring.num - 1)].flags &=
  			~VRING_DESC_F_NEXT;
@@ -584,6 +584,8 @@ static inline int virtqueue_add_split(struct virtqueue *_vq,
  					 total_sg * sizeof(struct vring_desc),
  					 VRING_DESC_F_INDIRECT,
  					 false);
+		vq->split.desc_extra[head & (vq->split.vring.num - 1)].flags &=
+			~VRING_DESC_F_NEXT;
  	}
/* We're using some buffers from the free list. */
@@ -693,7 +695,7 @@ static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head,
  	/* Put back on free list: unmap first-level descriptors and find end */
  	i = head;
- while (vq->split.vring.desc[i].flags & nextflag) {
+	while (vq->split.desc_extra[i].flags & nextflag) {
  		vring_unmap_one_split(vq, i);
  		i = vq->split.desc_extra[i].next;
  		vq->vq.num_free++;

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