[PATCH vhost v4 06/10] virtio_ring: no store dma info when unmap is not needed

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As discussed:
http://lore.kernel.org/all/CACGkMEug-=C+VQhkMYSgUKMC==04m7-uem_yC21bgGkKZh845w@xxxxxxxxxxxxxx

When the vq is premapped mode, the driver manages the dma
info is a good way.

So this commit make the virtio core not to store the dma
info and release the memory which is used to store the dma
info.

If the use_dma_api is false, the memory is also not allocated.

Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
---
 drivers/virtio/virtio_ring.c | 100 ++++++++++++++++++++++++++++++-----
 1 file changed, 87 insertions(+), 13 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 81a8c2b70af1..f5a72d22c838 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -94,12 +94,15 @@ struct vring_desc_state_packed {
 };
 
 struct vring_desc_extra {
-	dma_addr_t addr;		/* Descriptor DMA addr. */
-	u32 len;			/* Descriptor length. */
 	u16 flags;			/* Descriptor flags. */
 	u16 next;			/* The next desc state in a list. */
 };
 
+struct vring_desc_dma {
+	dma_addr_t addr;		/* Descriptor DMA addr. */
+	u32 len;			/* Descriptor length. */
+};
+
 struct vring_virtqueue_split {
 	/* Actual memory layout for this queue. */
 	struct vring vring;
@@ -116,6 +119,7 @@ struct vring_virtqueue_split {
 	/* Per-descriptor state. */
 	struct vring_desc_state_split *desc_state;
 	struct vring_desc_extra *desc_extra;
+	struct vring_desc_dma *desc_dma;
 
 	/* DMA address and size information */
 	dma_addr_t queue_dma_addr;
@@ -156,6 +160,7 @@ struct vring_virtqueue_packed {
 	/* Per-descriptor state. */
 	struct vring_desc_state_packed *desc_state;
 	struct vring_desc_extra *desc_extra;
+	struct vring_desc_dma *desc_dma;
 
 	/* DMA address and size information */
 	dma_addr_t ring_dma_addr;
@@ -470,13 +475,14 @@ static unsigned int vring_unmap_one_split(const struct vring_virtqueue *vq,
 					  unsigned int i)
 {
 	struct vring_desc_extra *extra = vq->split.desc_extra;
+	struct vring_desc_dma *dma = vq->split.desc_dma;
 	u16 flags;
 
 	flags = extra[i].flags;
 
 	dma_unmap_page(vring_dma_dev(vq),
-		       extra[i].addr,
-		       extra[i].len,
+		       dma[i].addr,
+		       dma[i].len,
 		       (flags & VRING_DESC_F_WRITE) ?
 		       DMA_FROM_DEVICE : DMA_TO_DEVICE);
 
@@ -533,8 +539,11 @@ static inline unsigned int virtqueue_add_desc_split(struct virtqueue *vq,
 		next = extra[i].next;
 		desc[i].next = cpu_to_virtio16(vq->vdev, next);
 
-		extra[i].addr = addr;
-		extra[i].len = len;
+		if (vring->split.desc_dma) {
+			vring->split.desc_dma[i].addr = addr;
+			vring->split.desc_dma[i].len = len;
+		}
+
 		extra[i].flags = flags;
 	} else
 		next = virtio16_to_cpu(vq->vdev, desc[i].next);
@@ -1070,6 +1079,23 @@ static void virtqueue_vring_attach_split(struct vring_virtqueue *vq,
 	vq->free_head = 0;
 }
 
+static int vring_alloc_dma_split(struct vring_virtqueue_split *vring_split,
+				  bool need_unmap)
+{
+	u32 num = vring_split->vring.num;
+	struct vring_desc_dma *dma;
+
+	if (!need_unmap)
+		return 0;
+
+	dma = kmalloc_array(num, sizeof(struct vring_desc_dma), GFP_KERNEL);
+	if (!dma)
+		return -ENOMEM;
+
+	vring_split->desc_dma = dma;
+	return 0;
+}
+
 static int vring_alloc_state_extra_split(struct vring_virtqueue_split *vring_split)
 {
 	struct vring_desc_state_split *state;
@@ -1106,6 +1132,7 @@ static void vring_free_split(struct vring_virtqueue_split *vring_split,
 
 	kfree(vring_split->desc_state);
 	kfree(vring_split->desc_extra);
+	kfree(vring_split->desc_dma);
 }
 
 static int vring_alloc_queue_split(struct vring_virtqueue_split *vring_split,
@@ -1207,6 +1234,10 @@ static int virtqueue_resize_split(struct virtqueue *_vq, u32 num)
 	if (err)
 		goto err_state_extra;
 
+	err = vring_alloc_dma_split(&vring_split, vring_need_unmap_buffer(vq));
+	if (err)
+		goto err_state_extra;
+
 	vring_free(&vq->vq);
 
 	virtqueue_vring_init_split(&vring_split, vq);
@@ -1239,14 +1270,16 @@ static u16 packed_last_used(u16 last_used_idx)
 
 /* caller must check vring_need_unmap_buffer() */
 static void vring_unmap_extra_packed(const struct vring_virtqueue *vq,
-				     const struct vring_desc_extra *extra)
+				     unsigned int i)
 {
+	const struct vring_desc_extra *extra = &vq->packed.desc_extra[i];
+	const struct vring_desc_dma *dma = &vq->packed.desc_dma[i];
 	u16 flags;
 
 	flags = extra->flags;
 
 	dma_unmap_page(vring_dma_dev(vq),
-		       extra->addr, extra->len,
+		       dma->addr, dma->len,
 		       (flags & VRING_DESC_F_WRITE) ?
 		       DMA_FROM_DEVICE : DMA_TO_DEVICE);
 }
@@ -1497,8 +1530,8 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
 			desc[i].id = cpu_to_le16(id);
 
 			if (vring_need_unmap_buffer(vq)) {
-				vq->packed.desc_extra[curr].addr = addr;
-				vq->packed.desc_extra[curr].len = sg->length;
+				vq->packed.desc_dma[curr].addr = addr;
+				vq->packed.desc_dma[curr].len = sg->length;
 			}
 
 			vq->packed.desc_extra[curr].flags = le16_to_cpu(flags);
@@ -1557,7 +1590,7 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
 	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, curr);
 		curr = vq->packed.desc_extra[curr].next;
 		i++;
 		if (i >= vq->packed.vring.num)
@@ -1638,8 +1671,7 @@ static void detach_buf_packed(struct vring_virtqueue *vq,
 		if (vring_need_unmap_buffer(vq)) {
 			curr = id;
 			for (i = 0; i < state->num; i++) {
-				vring_unmap_extra_packed(vq,
-							 &vq->packed.desc_extra[curr]);
+				vring_unmap_extra_packed(vq, curr);
 				curr = vq->packed.desc_extra[curr].next;
 			}
 		}
@@ -1952,6 +1984,7 @@ static void vring_free_packed(struct vring_virtqueue_packed *vring_packed,
 
 	kfree(vring_packed->desc_state);
 	kfree(vring_packed->desc_extra);
+	kfree(vring_packed->desc_dma);
 }
 
 static int vring_alloc_queue_packed(struct vring_virtqueue_packed *vring_packed,
@@ -2008,6 +2041,23 @@ static int vring_alloc_queue_packed(struct vring_virtqueue_packed *vring_packed,
 	return -ENOMEM;
 }
 
+static int vring_alloc_dma_packed(struct vring_virtqueue_packed *vring_packed,
+				  bool need_unmap)
+{
+	u32 num = vring_packed->vring.num;
+	struct vring_desc_dma *dma;
+
+	if (!need_unmap)
+		return 0;
+
+	dma = kmalloc_array(num, sizeof(struct vring_desc_dma), GFP_KERNEL);
+	if (!dma)
+		return -ENOMEM;
+
+	vring_packed->desc_dma = dma;
+	return 0;
+}
+
 static int vring_alloc_state_extra_packed(struct vring_virtqueue_packed *vring_packed)
 {
 	struct vring_desc_state_packed *state;
@@ -2120,6 +2170,10 @@ static struct virtqueue *vring_create_virtqueue_packed(struct virtio_device *vde
 	if (err)
 		goto err_state_extra;
 
+	err = vring_alloc_dma_packed(&vring_packed, vring_need_unmap_buffer(vq));
+	if (err)
+		goto err_state_extra;
+
 	virtqueue_vring_init_packed(&vring_packed, !!cfg_vq_val(cfg, callbacks));
 
 	virtqueue_init(vq, tp_cfg->num);
@@ -2152,6 +2206,10 @@ static int virtqueue_resize_packed(struct virtqueue *_vq, u32 num)
 	if (err)
 		goto err_state_extra;
 
+	err = vring_alloc_dma_packed(&vring_packed, vring_need_unmap_buffer(vq));
+	if (err)
+		goto err_state_extra;
+
 	vring_free(&vq->vq);
 
 	virtqueue_vring_init_packed(&vring_packed, !!vq->vq.callback);
@@ -2662,6 +2720,12 @@ static struct virtqueue *__vring_new_virtqueue(struct virtio_device *vdev,
 		return NULL;
 	}
 
+	err = vring_alloc_dma_split(vring_split, vring_need_unmap_buffer(vq));
+	if (err) {
+		kfree(vq);
+		return NULL;
+	}
+
 	virtqueue_vring_init_split(vring_split, vq);
 
 	virtqueue_init(vq, vring_split->vring.num);
@@ -2779,6 +2843,14 @@ int virtqueue_set_dma_premapped(struct virtqueue *_vq)
 
 	vq->premapped = true;
 
+	if (vq->packed_ring) {
+		kfree(vq->packed.desc_dma);
+		vq->packed.desc_dma = NULL;
+	} else {
+		kfree(vq->split.desc_dma);
+		vq->split.desc_dma = NULL;
+	}
+
 	END_USE(vq);
 
 	return 0;
@@ -2863,6 +2935,7 @@ static void vring_free(struct virtqueue *_vq)
 
 			kfree(vq->packed.desc_state);
 			kfree(vq->packed.desc_extra);
+			kfree(vq->packed.desc_dma);
 		} else {
 			vring_free_queue(vq->vq.vdev,
 					 vq->split.queue_size_in_bytes,
@@ -2874,6 +2947,7 @@ static void vring_free(struct virtqueue *_vq)
 	if (!vq->packed_ring) {
 		kfree(vq->split.desc_state);
 		kfree(vq->split.desc_extra);
+		kfree(vq->split.desc_dma);
 	}
 }
 
-- 
2.32.0.3.g01195cf9f





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