[PATCH vhost v3 06/19] virtio_ring: no store dma info when unmap is not needed

[Xuan Zhuo <xuanzhuo@linux.alibaba.com>]

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

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@linux.alibaba.com>
---
 drivers/virtio/virtio_ring.c | 89 ++++++++++++++++++++++++++++--------
 1 file changed, 70 insertions(+), 19 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 9680b3827d5b..c1e4edaeb446 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;
@@ -472,13 +477,14 @@ 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);
 
@@ -535,8 +541,11 @@ 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);
@@ -1072,16 +1081,26 @@ static void virtqueue_vring_attach_split(struct vring_virtqueue *vq,
 	vq->free_head = 0;
 }
 
-static int vring_alloc_state_extra_split(struct vring_virtqueue_split *vring_split)
+static int vring_alloc_state_extra_split(struct vring_virtqueue_split *vring_split,
+					 bool need_unmap)
 {
 	struct vring_desc_state_split *state;
 	struct vring_desc_extra *extra;
+	struct vring_desc_dma *dma;
 	u32 num = vring_split->vring.num;
 
 	state = kmalloc_array(num, sizeof(struct vring_desc_state_split), GFP_KERNEL);
 	if (!state)
 		goto err_state;
 
+	if (need_unmap) {
+		dma = kmalloc_array(num, sizeof(struct vring_desc_dma), GFP_KERNEL);
+		if (!dma)
+			goto err_dma;
+	} else {
+		dma = NULL;
+	}
+
 	extra = vring_alloc_desc_extra(num);
 	if (!extra)
 		goto err_extra;
@@ -1090,9 +1109,12 @@ static int vring_alloc_state_extra_split(struct vring_virtqueue_split *vring_spl
 
 	vring_split->desc_state = state;
 	vring_split->desc_extra = extra;
+	vring_split->desc_dma = dma;
 	return 0;
 
 err_extra:
+	kfree(dma);
+err_dma:
 	kfree(state);
 err_state:
 	return -ENOMEM;
@@ -1108,6 +1130,7 @@ 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,
@@ -1209,7 +1232,8 @@ static int virtqueue_resize_split(struct virtqueue *_vq, u32 num)
 	if (err)
 		goto err;
 
-	err = vring_alloc_state_extra_split(&vring_split);
+	err = vring_alloc_state_extra_split(&vring_split,
+					    vring_need_unmap_buffer(vq));
 	if (err)
 		goto err_state_extra;
 
@@ -1245,14 +1269,16 @@ 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);
 }
@@ -1503,8 +1529,8 @@ 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);
@@ -1563,7 +1589,7 @@ 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)
@@ -1644,8 +1670,7 @@ 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;
 			}
 		}
@@ -1958,6 +1983,7 @@ 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,
@@ -2014,10 +2040,12 @@ static int vring_alloc_queue_packed(struct vring_virtqueue_packed *vring_packed,
 	return -ENOMEM;
 }
 
-static int vring_alloc_state_extra_packed(struct vring_virtqueue_packed *vring_packed)
+static int vring_alloc_state_extra_packed(struct vring_virtqueue_packed *vring_packed,
+					  bool need_unmap)
 {
 	struct vring_desc_state_packed *state;
 	struct vring_desc_extra *extra;
+	struct vring_desc_dma *dma;
 	u32 num = vring_packed->vring.num;
 
 	state = kmalloc_array(num, sizeof(struct vring_desc_state_packed), GFP_KERNEL);
@@ -2026,6 +2054,14 @@ static int vring_alloc_state_extra_packed(struct vring_virtqueue_packed *vring_p
 
 	memset(state, 0, num * sizeof(struct vring_desc_state_packed));
 
+	if (need_unmap) {
+		dma = kmalloc_array(num, sizeof(struct vring_desc_dma), GFP_KERNEL);
+		if (!dma)
+			goto err_desc_dma;
+	} else {
+		dma = NULL;
+	}
+
 	extra = vring_alloc_desc_extra(num);
 	if (!extra)
 		goto err_desc_extra;
@@ -2036,6 +2072,8 @@ static int vring_alloc_state_extra_packed(struct vring_virtqueue_packed *vring_p
 	return 0;
 
 err_desc_extra:
+	kfree(dma);
+err_desc_dma:
 	kfree(state);
 err_desc_state:
 	return -ENOMEM;
@@ -2127,7 +2165,8 @@ static struct virtqueue *vring_create_virtqueue_packed(
 	if (virtio_has_feature(vdev, VIRTIO_F_ORDER_PLATFORM))
 		vq->weak_barriers = false;
 
-	err = vring_alloc_state_extra_packed(&vring_packed);
+	err = vring_alloc_state_extra_packed(&vring_packed,
+					     vring_need_unmap_buffer(vq));
 	if (err)
 		goto err_state_extra;
 
@@ -2159,7 +2198,8 @@ static int virtqueue_resize_packed(struct virtqueue *_vq, u32 num)
 	if (vring_alloc_queue_packed(&vring_packed, vdev, num, vring_dma_dev(vq)))
 		goto err_ring;
 
-	err = vring_alloc_state_extra_packed(&vring_packed);
+	err = vring_alloc_state_extra_packed(&vring_packed,
+					     vring_need_unmap_buffer(vq));
 	if (err)
 		goto err_state_extra;
 
@@ -2671,7 +2711,8 @@ static struct virtqueue *__vring_new_virtqueue(unsigned int index,
 	if (virtio_has_feature(vdev, VIRTIO_F_ORDER_PLATFORM))
 		vq->weak_barriers = false;
 
-	err = vring_alloc_state_extra_split(vring_split);
+	err = vring_alloc_state_extra_split(vring_split,
+					    vring_need_unmap_buffer(vq));
 	if (err) {
 		kfree(vq);
 		return NULL;
@@ -2831,6 +2872,14 @@ 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;
@@ -2920,6 +2969,7 @@ 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,
@@ -2931,6 +2981,7 @@ 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