Re: [RFC v2 5/7] virtio: unmask F_NEXT flag in desc_extra
From: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Date: 2022-08-18 03:10:02
Also in:
kvm, lkml, netdev
On Wed, 17 Aug 2022 21:57:16 +0800, Guo Zhi [off-list ref] wrote:
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.
I think we should state the purpose of this.
quoted hunk
Signed-off-by: Guo Zhi <redacted> --- 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;
This seems unnecessary.
quoted hunk
} /* 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) {
nextflag is __virtio16 You can use VRING_DESC_F_NEXT directly. Thanks.
vring_unmap_one_split(vq, i); i = vq->split.desc_extra[i].next; vq->vq.num_free++; -- 2.17.1
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