On Tue, Jun 16, 2020 at 02:07:19PM +0200, Daniel Vetter wrote: > > > I've pinged a bunch of armsoc gpu driver people and ask them how much this > > > hurts, so that we have a clear answer. On x86 I don't think we have much > > > of a choice on this, with userptr in amd and i915 and hmm work in nouveau > > > (but nouveau I think doesn't use dma_fence in there). > > > > Right, nor will RDMA ODP. > > Hm, what's the context here? I thought RDMA side you really don't want > dma_fence in mmu_notifiers, so not clear to me what you're agreeing on > here. rdma does not use dma_fence at all, and though it is hard to tell, I didn't notice a dma_fence in the nouveau invalidation call path. At the very least I think there should be some big warning that dma_fence in notifiers should be avoided. Ie it is strange that the new totally-not-a-gpu drivers use dma_fence, they surely don't have the same constraints as the existing GPU world, and it would be annoying to see dma_fence notifiers spring up in them Jason
