linux-kernel - [RFC PATCH 09/16] virtio_ring: packed: always update desc

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Date:   Sun, 24 Apr 2022 10:40:37 +0800
From:   Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To:     linux-kernel@...r.kernel.org
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        virtualization@...ts.linux-foundation.org
Subject: [RFC PATCH 09/16] virtio_ring: packed: always update desc_extra

No longer determine whether to update desc_extra based on use_dma_api.

Because desc will be modified by the device, in the process of resize,
if you want to reuse buffers, you can only get len and flags from
desc_extra.

Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
---
 drivers/virtio/virtio_ring.c | 22 +++++++++-------------
 1 file changed, 9 insertions(+), 13 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index e3525d92f646..436b18184dfe 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -1456,13 +1456,11 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
 				sizeof(struct vring_packed_desc));
 	vq->packed.vring.desc[head].id = cpu_to_le16(id);
 
-	if (vq->use_dma_api) {
-		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].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;
 
 	/*
 	 * A driver MUST NOT make the first descriptor in the list
@@ -1592,12 +1590,10 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
 			desc[i].len = cpu_to_le32(sg->length);
 			desc[i].id = cpu_to_le16(id);
 
-			if (unlikely(vq->use_dma_api)) {
-				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].addr = addr;
+			vq->packed.desc_extra[curr].len = sg->length;
+			vq->packed.desc_extra[curr].flags = le16_to_cpu(flags);
+
 			prev = curr;
 			curr = vq->packed.desc_extra[curr].next;
 
-- 
2.31.0