On Mon, Feb 19, 2024 at 06:06:06PM +0100, Maxime Coquelin wrote:
Since commit 295525e29a5b ("virtio_net: merge dma
operations when filling mergeable buffers"), VDUSE device
require support for DMA's .sync_single_for_cpu() operation
as the memory is non-coherent between the device and CPU
because of the use of a bounce buffer.
This patch implements both .sync_single_for_cpu() and
sync_single_for_device() callbacks, and also skip bounce
buffer copies during DMA map and unmap operations if the
DMA_ATTR_SKIP_CPU_SYNC attribute is set to avoid extra
copies of the same buffer.
vduse really needs to get out of implementing fake DMA operations for
something that is not DMA.