On Tue, Oct 6, 2020 at 6:34 PM Daniel Vetter <daniel@xxxxxxxx> wrote: > > On Tue, Oct 06, 2020 at 12:49:56PM -0300, Jason Gunthorpe wrote: > > On Tue, Oct 06, 2020 at 11:22:14AM +0200, Daniel Vetter wrote: > > > > > > For reinstanting the pages you need: > > > > > > - dma_resv_lock, this prevents anyone else from issuing new moves or > > > anything like that > > > - dma_resv_get_excl + dma_fence_wait to wait for any pending moves to > > > finish. gpus generally don't wait on the cpu, but block the dependent > > > dma operations from being scheduled until that fence fired. But for rdma > > > odp I think you need the cpu wait in your worker here. > > > > Reinstating is not really any different that the first insertion, so > > then all this should be needed in every case? > > Yes. Without move_notify we pin the dma-buf into system memory, so it > can't move, and hence you also don't have to chase it. But with > move_notify this all becomes possible. I just realized I got it wrong compared to gpus. I needs to be: 1. dma_resv_lock 2. dma_buf_map_attachment, which might have to move the buffer around again if you're unlucky 3. wait for the exclusive fence 4. put sgt into your rdma ptes 5 dma_resv_unlock Maybe also something we should document somewhere for dynamic buffers. Assuming I got it right this time around ... Christian? -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
