[RFC LINUX PATCH 0/2] Virtio ring works with DMA coherent memory

[Wendy Liang <wendy.liang@xilinx.com>]

RPMsg uses dma_alloc_coherent() to allocate memory to shared with the remote.
In this case, as there is no pages setup in the dma_alloc_coherent(),
we cannot get the physical address back from the virtual address, and thus,
we can set the sg_dma_addr to store the DMA address and mark it already DMA
mapped.

When virtio vring sees the sg_dma_addr is ready set, do not call dma_map_page().

The issue was once discussed here:
http://virtualization.linux-foundation.narkive.com/CfVP32Vy/rfc-0-4-rpmsg-fix-init-of-dma-able-virtqueues

Edgar E. Iglesias (1):
  rpmsg: DMA map sgs passed to virtio

Wendy Liang (1):
  virtio_ring: Do not call dma_map_page if sg is already mapped.

 drivers/rpmsg/virtio_rpmsg_bus.c | 22 +++++++++++++++++++---
 drivers/virtio/virtio_ring.c     |  6 ++++++
 2 files changed, 25 insertions(+), 3 deletions(-)

-- 
1.9.1