When a descriptor list spans across cache lines, updating the flag first can lead to a scenario where the device side perceives the flag as valid, yet the corresponding address and length fields remain unupdated—resulting in invalid values. Therefore, the flag field must be updated last.
Signed-off-by: yangjiale <[email protected]> --- drivers/virtio/virtio_ring.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index fbca7ce1c6bf..036b4f90d30f 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -1688,6 +1688,10 @@ static inline int virtqueue_add_packed(struct vring_virtqueue *vq, &addr, &len, premapped, attr)) goto unmap_release; + desc[i].addr = cpu_to_le64(addr); + desc[i].len = cpu_to_le32(len); + desc[i].id = cpu_to_le16(id); + flags = cpu_to_le16(vq->packed.avail_used_flags | (++c == total_sg ? 0 : VRING_DESC_F_NEXT) | (n < out_sgs ? 0 : VRING_DESC_F_WRITE)); @@ -1696,10 +1700,6 @@ static inline int virtqueue_add_packed(struct vring_virtqueue *vq, else desc[i].flags = flags; - desc[i].addr = cpu_to_le64(addr); - desc[i].len = cpu_to_le32(len); - desc[i].id = cpu_to_le16(id); - if (unlikely(vq->use_map_api)) { vq->packed.desc_extra[curr].addr = premapped ? DMA_MAPPING_ERROR : addr; -- 2.25.1
