If sg is already dma mapped, do not call dma_map_page() in vring_map_one_sg().
In case of rpmsg, rpmsg uses dma_alloc_coherent() to allocate memory to share with the remote. There is no pages setup in dma_alloc_coherent(). In this case, we cannot convert the virtual address back to the physical address. In this case, we can setup the sg_dma_addr to store the DMA address, and also mark the sg is already mapped. In the vring, we can detect if the address is already mapped by checking the sg_dma_addr. If yes, do not call dma_map_page(). Signed-off-by: Wendy Liang <[email protected]> --- drivers/virtio/virtio_ring.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 489bfc6..9793e1f 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -180,6 +180,12 @@ static dma_addr_t vring_map_one_sg(const struct vring_virtqueue *vq, if (!vring_use_dma_api(vq->vq.vdev)) return (dma_addr_t)sg_phys(sg); + /* If the sg is already mapped, return the DMA address */ + if (sg_dma_address(sg)) { + sg->length = sg_dma_len(sg); + return sg_dma_address(sg); + } + /* * We can't use dma_map_sg, because we don't use scatterlists in * the way it expects (we don't guarantee that the scatterlist -- 1.9.1 _______________________________________________ Virtualization mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/virtualization
