[PATCH 02/33] virtio_ring: split: virtqueue_add_split() support premapped

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virtqueue_add_split() only supports virtual addresses, dma is completed
in virtqueue_add_split().

In some scenarios (such as the AF_XDP scenario), the memory is allocated
and DMA is completed in advance, so it is necessary for us to support
passing the DMA address to virtqueue_add_split().

Record this information in desc_state, we can skip unmap based on this
when executing dma unmap.

Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
---
 drivers/virtio/virtio_ring.c | 55 +++++++++++++++++++++++++++---------
 1 file changed, 42 insertions(+), 13 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index c9f194c86aec..ec622403cbd5 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -70,6 +70,7 @@
 struct vring_desc_state_split {
 	void *data;			/* Data for callback. */
 	struct vring_desc *indir_desc;	/* Indirect descriptor, if any. */
+	bool premapped;
 };
 
 struct vring_desc_state_packed {
@@ -434,7 +435,7 @@ static void vring_unmap_one_split_indirect(const struct vring_virtqueue *vq,
 }
 
 static unsigned int vring_unmap_one_split(const struct vring_virtqueue *vq,
-					  unsigned int i)
+					  unsigned int i, bool premapped)
 {
 	struct vring_desc_extra *extra = vq->split.desc_extra;
 	u16 flags;
@@ -451,6 +452,9 @@ static unsigned int vring_unmap_one_split(const struct vring_virtqueue *vq,
 				 (flags & VRING_DESC_F_WRITE) ?
 				 DMA_FROM_DEVICE : DMA_TO_DEVICE);
 	} else {
+		if (premapped)
+			goto out;
+
 		dma_unmap_page(vring_dma_dev(vq),
 			       extra[i].addr,
 			       extra[i].len,
@@ -521,6 +525,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq,
 				      unsigned int in_sgs,
 				      void *data,
 				      void *ctx,
+				      bool premapped,
 				      gfp_t gfp)
 {
 	struct vring_virtqueue *vq = to_vvq(_vq);
@@ -582,9 +587,16 @@ static inline int virtqueue_add_split(struct virtqueue *_vq,
 
 	for (n = 0; n < out_sgs; n++) {
 		for (sg = sgs[n]; sg; sg = sg_next(sg)) {
-			dma_addr_t addr = vring_map_one_sg(vq, sg, DMA_TO_DEVICE);
-			if (vring_mapping_error(vq, addr))
-				goto unmap_release;
+			dma_addr_t addr;
+
+			if (premapped) {
+				addr = sg_dma_address(sg);
+
+			} else {
+				addr = vring_map_one_sg(vq, sg, DMA_TO_DEVICE);
+				if (vring_mapping_error(vq, addr))
+					goto unmap_release;
+			}
 
 			prev = i;
 			/* Note that we trust indirect descriptor
@@ -597,9 +609,16 @@ static inline int virtqueue_add_split(struct virtqueue *_vq,
 	}
 	for (; n < (out_sgs + in_sgs); n++) {
 		for (sg = sgs[n]; sg; sg = sg_next(sg)) {
-			dma_addr_t addr = vring_map_one_sg(vq, sg, DMA_FROM_DEVICE);
-			if (vring_mapping_error(vq, addr))
-				goto unmap_release;
+			dma_addr_t addr;
+
+			if (premapped) {
+				addr = sg_dma_address(sg);
+
+			} else {
+				addr = vring_map_one_sg(vq, sg, DMA_FROM_DEVICE);
+				if (vring_mapping_error(vq, addr))
+					goto unmap_release;
+			}
 
 			prev = i;
 			/* Note that we trust indirect descriptor
@@ -644,6 +663,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq,
 
 	/* Store token and indirect buffer state. */
 	vq->split.desc_state[head].data = data;
+	vq->split.desc_state[head].premapped = premapped;
 	if (indirect)
 		vq->split.desc_state[head].indir_desc = desc;
 	else
@@ -673,6 +693,9 @@ static inline int virtqueue_add_split(struct virtqueue *_vq,
 	return 0;
 
 unmap_release:
+	if (premapped)
+		goto unmap_free;
+
 	err_idx = i;
 
 	if (indirect)
@@ -687,9 +710,10 @@ static inline int virtqueue_add_split(struct virtqueue *_vq,
 			vring_unmap_one_split_indirect(vq, &desc[i]);
 			i = virtio16_to_cpu(_vq->vdev, desc[i].next);
 		} else
-			i = vring_unmap_one_split(vq, i);
+			i = vring_unmap_one_split(vq, i, false);
 	}
 
+unmap_free:
 	if (indirect)
 		kfree(desc);
 
@@ -733,20 +757,23 @@ static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head,
 {
 	unsigned int i, j;
 	__virtio16 nextflag = cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT);
+	bool premapped;
 
 	/* Clear data ptr. */
 	vq->split.desc_state[head].data = NULL;
 
+	premapped = vq->split.desc_state[head].premapped;
+
 	/* Put back on free list: unmap first-level descriptors and find end */
 	i = head;
 
 	while (vq->split.vring.desc[i].flags & nextflag) {
-		vring_unmap_one_split(vq, i);
+		vring_unmap_one_split(vq, i, premapped);
 		i = vq->split.desc_extra[i].next;
 		vq->vq.num_free++;
 	}
 
-	vring_unmap_one_split(vq, i);
+	vring_unmap_one_split(vq, i, premapped);
 	vq->split.desc_extra[i].next = vq->free_head;
 	vq->free_head = head;
 
@@ -768,8 +795,10 @@ static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head,
 				VRING_DESC_F_INDIRECT));
 		BUG_ON(len == 0 || len % sizeof(struct vring_desc));
 
-		for (j = 0; j < len / sizeof(struct vring_desc); j++)
-			vring_unmap_one_split_indirect(vq, &indir_desc[j]);
+		if (!premapped) {
+			for (j = 0; j < len / sizeof(struct vring_desc); j++)
+				vring_unmap_one_split_indirect(vq, &indir_desc[j]);
+		}
 
 		kfree(indir_desc);
 		vq->split.desc_state[head].indir_desc = NULL;
@@ -2095,7 +2124,7 @@ static inline int virtqueue_add(struct virtqueue *_vq,
 	return vq->packed_ring ? virtqueue_add_packed(_vq, sgs, total_sg,
 					out_sgs, in_sgs, data, ctx, gfp) :
 				 virtqueue_add_split(_vq, sgs, total_sg,
-					out_sgs, in_sgs, data, ctx, gfp);
+					out_sgs, in_sgs, data, ctx, premapped, gfp);
 }
 
 /**
-- 
2.32.0.3.g01195cf9f




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