[PATCH] virtio_ring: skip cpu sync when mapping fails

Jason Wang
2024-11-11T02:55:51Z

There's no need to sync DMA for CPU on mapping errors. So this patch
skips the CPU sync in the error handling path of DMA mapping.

Signed-off-by: Jason Wang <jasowang@redhat.com>
---
drivers/virtio/virtio_ring.c | 98 +++++++++++++++++++++---------------
1 file changed, 57 insertions(+), 41 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index be7309b1e860..b422b5fb22db 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -441,8 +441,10 @@ static void virtqueue_init(struct vring_virtqueue *vq, u32 num)
*/

static void vring_unmap_one_split_indirect(const struct vring_virtqueue *vq,
- const struct vring_desc *desc)
+ const struct vring_desc *desc,
+ bool skip_sync)
{
+ unsigned long attrs = skip_sync ? DMA_ATTR_SKIP_CPU_SYNC : 0;
u16 flags;

if (!vq->do_unmap)
@@ -450,16 +452,18 @@ static void vring_unmap_one_split_indirect(const struct vring_virtqueue *vq,

flags = virtio16_to_cpu(vq->vq.vdev, desc->flags);

- dma_unmap_page(vring_dma_dev(vq),
- virtio64_to_cpu(vq->vq.vdev, desc->addr),
- virtio32_to_cpu(vq->vq.vdev, desc->len),
- (flags & VRING_DESC_F_WRITE) ?
- DMA_FROM_DEVICE : DMA_TO_DEVICE);
+ dma_unmap_page_attrs(vring_dma_dev(vq),
+ virtio64_to_cpu(vq->vq.vdev, desc->addr),
+ virtio32_to_cpu(vq->vq.vdev, desc->len),
+ (flags & VRING_DESC_F_WRITE) ?
+ DMA_FROM_DEVICE : DMA_TO_DEVICE,
+ attrs);
}

static unsigned int vring_unmap_one_split(const struct vring_virtqueue *vq,
- unsigned int i)
+ unsigned int i, bool skip_sync)
{
+ unsigned long attrs = skip_sync ? DMA_ATTR_SKIP_CPU_SYNC : 0;
struct vring_desc_extra *extra = vq->split.desc_extra;
u16 flags;

@@ -469,20 +473,22 @@ static unsigned int vring_unmap_one_split(const struct vring_virtqueue *vq,
if (!vq->use_dma_api)
goto out;

- dma_unmap_single(vring_dma_dev(vq),
- extra[i].addr,
- extra[i].len,
- (flags & VRING_DESC_F_WRITE) ?
- DMA_FROM_DEVICE : DMA_TO_DEVICE);
+ dma_unmap_single_attrs(vring_dma_dev(vq),
+ extra[i].addr,
+ extra[i].len,
+ (flags & VRING_DESC_F_WRITE) ?
+ DMA_FROM_DEVICE : DMA_TO_DEVICE,
+ attrs);
} else {
if (!vq->do_unmap)
goto out;

- dma_unmap_page(vring_dma_dev(vq),
- extra[i].addr,
- extra[i].len,
- (flags & VRING_DESC_F_WRITE) ?
- DMA_FROM_DEVICE : DMA_TO_DEVICE);
+ dma_unmap_page_attrs(vring_dma_dev(vq),
+ extra[i].addr,
+ extra[i].len,
+ (flags & VRING_DESC_F_WRITE) ?
+ DMA_FROM_DEVICE : DMA_TO_DEVICE,
+ attrs);
}

out:
@@ -717,10 +723,10 @@ static inline int virtqueue_add_split(struct virtqueue *_vq,
if (i == err_idx)
break;
if (indirect) {
- vring_unmap_one_split_indirect(vq, &desc[i]);
+ vring_unmap_one_split_indirect(vq, &desc[i], true);
i = virtio16_to_cpu(_vq->vdev, desc[i].next);
} else
- i = vring_unmap_one_split(vq, i);
+ i = vring_unmap_one_split(vq, i, true);
}

free_indirect:
@@ -775,12 +781,12 @@ static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head,
i = head;

while (vq->split.vring.desc[i].flags & nextflag) {
- vring_unmap_one_split(vq, i);
+ vring_unmap_one_split(vq, i, false);
i = vq->split.desc_extra[i].next;
vq->vq.num_free++;
}

- vring_unmap_one_split(vq, i);
+ vring_unmap_one_split(vq, i, false);
vq->split.desc_extra[i].next = vq->free_head;
vq->free_head = head;

@@ -804,7 +810,8 @@ static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head,

if (vq->do_unmap) {
for (j = 0; j < len / sizeof(struct vring_desc); j++)
- vring_unmap_one_split_indirect(vq, &indir_desc[j]);
+ vring_unmap_one_split_indirect(vq,
+ &indir_desc[j], false);
}

kfree(indir_desc);
@@ -1221,8 +1228,10 @@ static u16 packed_last_used(u16 last_used_idx)
}

static void vring_unmap_extra_packed(const struct vring_virtqueue *vq,
- const struct vring_desc_extra *extra)
+ const struct vring_desc_extra *extra,
+ bool skip_sync)
{
+ unsigned long attrs = skip_sync ? DMA_ATTR_SKIP_CPU_SYNC : 0;
u16 flags;

flags = extra->flags;
@@ -1231,24 +1240,28 @@ static void vring_unmap_extra_packed(const struct vring_virtqueue *vq,
if (!vq->use_dma_api)
return;

- dma_unmap_single(vring_dma_dev(vq),
- extra->addr, extra->len,
- (flags & VRING_DESC_F_WRITE) ?
- DMA_FROM_DEVICE : DMA_TO_DEVICE);
+ dma_unmap_single_attrs(vring_dma_dev(vq),
+ extra->addr, extra->len,
+ (flags & VRING_DESC_F_WRITE) ?
+ DMA_FROM_DEVICE : DMA_TO_DEVICE,
+ attrs);
} else {
if (!vq->do_unmap)
return;

- dma_unmap_page(vring_dma_dev(vq),
- extra->addr, extra->len,
- (flags & VRING_DESC_F_WRITE) ?
- DMA_FROM_DEVICE : DMA_TO_DEVICE);
+ dma_unmap_page_attrs(vring_dma_dev(vq),
+ extra->addr, extra->len,
+ (flags & VRING_DESC_F_WRITE) ?
+ DMA_FROM_DEVICE : DMA_TO_DEVICE,
+ attrs);
}
}

static void vring_unmap_desc_packed(const struct vring_virtqueue *vq,
- const struct vring_packed_desc *desc)
+ const struct vring_packed_desc *desc,
+ bool skip_sync)
{
+ unsigned long attrs = skip_sync ? DMA_ATTR_SKIP_CPU_SYNC : 0;
u16 flags;

if (!vq->do_unmap)
@@ -1256,11 +1269,12 @@ static void vring_unmap_desc_packed(const struct vring_virtqueue *vq,

flags = le16_to_cpu(desc->flags);

- dma_unmap_page(vring_dma_dev(vq),
- le64_to_cpu(desc->addr),
- le32_to_cpu(desc->len),
- (flags & VRING_DESC_F_WRITE) ?
- DMA_FROM_DEVICE : DMA_TO_DEVICE);
+ dma_unmap_page_attrs(vring_dma_dev(vq),
+ le64_to_cpu(desc->addr),
+ le32_to_cpu(desc->len),
+ (flags & VRING_DESC_F_WRITE) ?
+ DMA_FROM_DEVICE : DMA_TO_DEVICE,
+ attrs);
}

static struct vring_packed_desc *alloc_indirect_packed(unsigned int total_sg,
@@ -1389,7 +1403,7 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
err_idx = i;

for (i = 0; i < err_idx; i++)
- vring_unmap_desc_packed(vq, &desc[i]);
+ vring_unmap_desc_packed(vq, &desc[i], true);

free_desc:
kfree(desc);
@@ -1539,7 +1553,8 @@ 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,
+ &vq->packed.desc_extra[curr], true);
curr = vq->packed.desc_extra[curr].next;
i++;
if (i >= vq->packed.vring.num)
@@ -1619,7 +1634,8 @@ 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],
+ false);
curr = vq->packed.desc_extra[curr].next;
}
}
@@ -1636,7 +1652,7 @@ static void detach_buf_packed(struct vring_virtqueue *vq,
len = vq->packed.desc_extra[id].len;
for (i = 0; i < len / sizeof(struct vring_packed_desc);
i++)
- vring_unmap_desc_packed(vq, &desc[i]);
+ vring_unmap_desc_packed(vq, &desc[i], false);
}
kfree(desc);
state->indir_desc = NULL;
--
2.31.1