virtio core only supports virtual addresses, dma is completed in virtio
core.
In some scenarios (such as the AF_XDP), the memory is allocated
and DMA is completed in advance, so it is necessary for us to support
passing the DMA address to virtio core.
Drives can use sg->dma_address to pass the mapped dma address to virtio
core. If one sg->dma_address is used then all sgs must use sg->dma_address,
otherwise all dma_address must be null.
On the non-indirect path, if dma_address is used, extra.addr will be
set to DMA_MAPPING_ERROR. So when do unmap, we can pass it.
Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
---
drivers/virtio/virtio_ring.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 61deaf0a4faf..66a071e3bdef 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -1258,6 +1258,9 @@ static void vring_unmap_extra_packed(const struct vring_virtqueue *vq,
(flags & VRING_DESC_F_WRITE) ?
DMA_FROM_DEVICE : DMA_TO_DEVICE);
} else {
+ if (extra->addr == DMA_MAPPING_ERROR)
+ return;
+
dma_unmap_page(vring_dma_dev(vq),
extra->addr, extra->len,
(flags & VRING_DESC_F_WRITE) ?
@@ -1423,6 +1426,7 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
unsigned int i, n, c, descs_used;
__le16 head_flags, flags;
u16 head, id, prev, curr;
+ bool do_map;
int err;
START_USE(vq);
@@ -1468,7 +1472,8 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
id = vq->free_head;
BUG_ON(id == vq->packed.vring.num);
- if (virtqueue_map_sgs(vq, sgs, total_sg, out_sgs, in_sgs))
+ do_map = !sgs[0]->dma_address;
+ if (do_map && virtqueue_map_sgs(vq, sgs, total_sg, out_sgs, in_sgs))
return -ENOMEM;
curr = id;
@@ -1488,7 +1493,8 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
desc[i].id = cpu_to_le16(id);
if (unlikely(vq->use_dma_api)) {
- vq->packed.desc_extra[curr].addr = sg->dma_address;
+ vq->packed.desc_extra[curr].addr =
+ do_map ? sg->dma_address : DMA_MAPPING_ERROR;
vq->packed.desc_extra[curr].len = sg->length;
vq->packed.desc_extra[curr].flags =
le16_to_cpu(flags);
--
2.32.0.3.g01195cf9f
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