linux-kernel - [RFC v3 5/7] virtio: unmask F_NEXT flag in desc

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Message-Id: <20220901055434.824-6-qtxuning1999@sjtu.edu.cn>
Date:   Thu,  1 Sep 2022 13:54:32 +0800
From:   Guo Zhi <qtxuning1999@...u.edu.cn>
To:     eperezma@...hat.com, jasowang@...hat.com, sgarzare@...hat.com,
        mst@...hat.com
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        Guo Zhi <qtxuning1999@...u.edu.cn>
Subject: [RFC v3 5/7] virtio: unmask F_NEXT flag in desc_extra

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@...u.edu.cn>
---
 drivers/virtio/virtio_ring.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index a5ec724c01d8..00aa4b7a49c2 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. */
@@ -685,7 +687,6 @@ static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head,
 			     void **ctx)
 {
 	unsigned int i, j;
-	__virtio16 nextflag = cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT);
 
 	/* Clear data ptr. */
 	vq->split.desc_state[head].data = NULL;
@@ -693,7 +694,7 @@ 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 & VRING_DESC_F_NEXT) {
 		vring_unmap_one_split(vq, i);
 		i = vq->split.desc_extra[i].next;
 		vq->vq.num_free++;
-- 
2.17.1