On Mon, Dec 28, 2020 at 4:43 PM Jason Wang <jasowang@xxxxxxxxxx> wrote: > > > On 2020/12/28 下午4:14, Yongji Xie wrote: > >> I see. So all the above two questions are because VHOST_IOTLB_INVALIDATE > >> is expected to be synchronous. This need to be solved by tweaking the > >> current VDUSE API or we can re-visit to go with descriptors relaying first. > >> > > Actually all vdpa related operations are synchronous in current > > implementation. The ops.set_map/dma_map/dma_unmap should not return > > until the VDUSE_UPDATE_IOTLB/VDUSE_INVALIDATE_IOTLB message is replied > > by userspace. Could it solve this problem? > > > I was thinking whether or not we need to generate IOTLB_INVALIDATE > message to VDUSE during dma_unmap (vduse_dev_unmap_page). > > If we don't, we're probably fine. > It seems not feasible. This message will be also used in the virtio-vdpa case to notify userspace to unmap some pages during consistent dma unmapping. Maybe we can document it to make sure the users can handle the message correctly. Thanks, Yongji
