Re: [PATCH v1 6/6] virtio: packed: virtqueue_add_packed() support dma address

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在 2022/2/10 下午4:51, Xuan Zhuo 写道:

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

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_packed().

Record this predma information in extra->flags, which can be skipped
when executing dma unmap.

Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>



Except for the similar comments as split version other looks good.

Thanks



---
  drivers/virtio/virtio_ring.c | 79 ++++++++++++++++++++++++++----------
  1 file changed, 57 insertions(+), 22 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index d32c0bf6016f..b8c7697e925d 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -1011,7 +1011,8 @@ static struct virtqueue *vring_create_virtqueue_split(
   */
static void vring_unmap_extra_packed(const struct vring_virtqueue *vq, 
-				     struct vring_desc_extra *extra)
+				     struct vring_desc_extra *extra,
+				     bool predma)
  {
  	u16 flags;
@@ -1026,6 +1027,9 @@ static void vring_unmap_extra_packed(const struct vring_virtqueue *vq, 
  				 (flags & VRING_DESC_F_WRITE) ?
  				 DMA_FROM_DEVICE : DMA_TO_DEVICE);
  	} else {
+		if (predma)
+			return;
+
  		dma_unmap_page(vring_dma_dev(vq),
  			       extra->addr, extra->len,
  			       (flags & VRING_DESC_F_WRITE) ?
@@ -1073,7 +1077,8 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
  					 unsigned int out_sgs,
  					 unsigned int in_sgs,
  					 void *data,
-					 gfp_t gfp)
+					 gfp_t gfp,
+					 bool predma)
  {
  	struct vring_packed_desc *desc;
  	struct scatterlist *sg;
@@ -1099,10 +1104,15 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
for (n = 0; n < out_sgs + in_sgs; n++) { 
  		for (sg = sgs[n]; sg; sg = sg_next(sg)) {
-			addr = vring_map_one_sg(vq, sg, n < out_sgs ?
-					DMA_TO_DEVICE : DMA_FROM_DEVICE);
-			if (vring_mapping_error(vq, addr))
-				goto unmap_release;
+			if (predma) {
+				addr = sg_dma_address(sg);
+
+			} else {
+				addr = vring_map_one_sg(vq, sg, n < out_sgs ?
+							DMA_TO_DEVICE : DMA_FROM_DEVICE);
+				if (vring_mapping_error(vq, addr))
+					goto unmap_release;
+			}
desc[i].flags = cpu_to_le16(n < out_sgs ? 
  						0 : VRING_DESC_F_WRITE);
@@ -1132,6 +1142,9 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
  						  vq->packed.avail_used_flags;
  	}
+ if (predma) 
+		vq->packed.desc_extra[id].flags |= VIRTIO_DESC_F_PREDMA;
+
  	/*
  	 * A driver MUST NOT make the first descriptor in the list
  	 * available before all subsequent descriptors comprising
@@ -1170,10 +1183,11 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
  	return 0;
unmap_release: 
-	err_idx = i;
-
-	for (i = 0; i < err_idx; i++)
-		vring_unmap_desc_packed(vq, &desc[i]);
+	if (!predma) {
+		err_idx = i;
+		for (i = 0; i < err_idx; i++)
+			vring_unmap_desc_packed(vq, &desc[i]);
+	}
kfree(desc); @@ -1188,7 +1202,8 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq, 
  				       unsigned int in_sgs,
  				       void *data,
  				       void *ctx,
-				       gfp_t gfp)
+				       gfp_t gfp,
+				       bool predma)
  {
  	struct vring_virtqueue *vq = to_vvq(_vq);
  	struct vring_packed_desc *desc;
@@ -1214,7 +1229,7 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
if (virtqueue_use_indirect(_vq, total_sg)) { 
  		err = virtqueue_add_indirect_packed(vq, sgs, total_sg, out_sgs,
-						    in_sgs, data, gfp);
+						    in_sgs, data, gfp, predma);
  		if (err != -ENOMEM) {
  			END_USE(vq);
  			return err;
@@ -1246,10 +1261,17 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
  	c = 0;
  	for (n = 0; 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, n < out_sgs ?
-					DMA_TO_DEVICE : DMA_FROM_DEVICE);
-			if (vring_mapping_error(vq, addr))
-				goto unmap_release;
+			dma_addr_t addr;
+
+			if (predma) {
+				addr = sg_dma_address(sg);
+
+			} else {
+				addr = vring_map_one_sg(vq, sg, n < out_sgs ?
+							DMA_TO_DEVICE : DMA_FROM_DEVICE);
+				if (vring_mapping_error(vq, addr))
+					goto unmap_release;
+			}
flags = cpu_to_le16(vq->packed.avail_used_flags | 
  				    (++c == total_sg ? 0 : VRING_DESC_F_NEXT) |
@@ -1297,6 +1319,9 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
  	vq->packed.desc_state[id].indir_desc = ctx;
  	vq->packed.desc_state[id].last = prev;
+ if (predma) 
+		vq->packed.desc_extra[id].flags |= VIRTIO_DESC_F_PREDMA;
+
  	/*
  	 * A driver MUST NOT make the first descriptor in the list
  	 * available before all subsequent descriptors comprising
@@ -1312,22 +1337,27 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
  	return 0;
unmap_release: 
+	vq->packed.avail_used_flags = avail_used_flags;
+
+	if (predma)
+		goto skip_unmap;
+
  	err_idx = i;
  	i = head;
  	curr = vq->free_head;
- vq->packed.avail_used_flags = avail_used_flags; 
-
  	for (n = 0; n < total_sg; n++) {
  		if (i == err_idx)
  			break;
-		vring_unmap_extra_packed(vq, &vq->packed.desc_extra[curr]);
+		vring_unmap_extra_packed(vq, &vq->packed.desc_extra[curr], false);
  		curr = vq->packed.desc_extra[curr].next;
  		i++;
  		if (i >= vq->packed.vring.num)
  			i = 0;
  	}
+skip_unmap: 
+
  	END_USE(vq);
  	return -EIO;
  }
@@ -1387,9 +1417,13 @@ static void detach_buf_packed(struct vring_virtqueue *vq,
  	struct vring_desc_state_packed *state = NULL;
  	struct vring_packed_desc *desc;
  	unsigned int i, curr;
+	bool predma = false;
state = &vq->packed.desc_state[id]; + if (vq->packed.desc_extra[state->last].flags & VIRTIO_DESC_F_PREDMA) 
+		predma = true;
+
  	/* Clear data ptr. */
  	state->data = NULL;
@@ -1401,7 +1435,8 @@ static void detach_buf_packed(struct vring_virtqueue *vq, 
  		curr = id;
  		for (i = 0; i < state->num; i++) {
  			vring_unmap_extra_packed(vq,
-						 &vq->packed.desc_extra[curr]);
+						 &vq->packed.desc_extra[curr],
+						 predma);
  			curr = vq->packed.desc_extra[curr].next;
  		}
  	}
@@ -1414,7 +1449,7 @@ static void detach_buf_packed(struct vring_virtqueue *vq,
  		if (!desc)
  			return;
- if (vq->use_dma_api) { 
+		if (vq->use_dma_api && !predma) {
  			len = vq->packed.desc_extra[id].len;
  			for (i = 0; i < len / sizeof(struct vring_packed_desc);
  					i++)
@@ -1820,7 +1855,7 @@ static inline int virtqueue_add(struct virtqueue *_vq,
  	struct vring_virtqueue *vq = to_vvq(_vq);
return vq->packed_ring ? virtqueue_add_packed(_vq, sgs, total_sg, 
-					out_sgs, in_sgs, data, ctx, gfp) :
+					out_sgs, in_sgs, data, ctx, gfp, predma) :
  				 virtqueue_add_split(_vq, sgs, total_sg,
  					out_sgs, in_sgs, data, ctx, gfp, predma);
  }


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