Pulling this out of the shadows again. We now also have xen-zcopy from Oleksandr and the hyper dmabuf stuff from Matt and Dongwong. At least from the intel side there seems to be the idea to just have 1 special device that can handle cross-gues/host sharing for all kinds of hypervisors, so I guess you all need to work together :-) Or we throw out the idea that hyper dmabuf will be cross-hypervisor (not sure how useful/reasonable that is, someone please convince me one way or the other). Cheers, Daniel On Wed, Mar 14, 2018 at 9:03 AM, Gerd Hoffmann <kraxel@xxxxxxxxxx> wrote: > Hi, > >> Either mlock account (because it's mlocked defacto), and get_user_pages >> won't do that for you. >> >> Or you write the full-blown userptr implementation, including mmu_notifier >> support (see i915 or amdgpu), but that also requires Christian Königs >> latest ->invalidate_mapping RFC for dma-buf (since atm exporting userptr >> buffers is a no-go). > > I guess I'll look at mlock accounting for starters then. Easier for > now, and leaves the door open to switch to userptr later as this should > be transparent to userspace. > >> > Known issue: Driver API isn't complete yet. Need add some flags, for >> > example to support read-only buffers. >> >> dma-buf has no concept of read-only. I don't think we can even enforce >> that (not many iommus can enforce this iirc), so pretty much need to >> require r/w memory. > > Ah, ok. Just saw the 'write' arg for get_user_pages_fast and figured we > might support that, but if iommus can't handle that anyway it's > pointless indeed. > >> > Cc: David Airlie <airlied@xxxxxxxx> >> > Cc: Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx> >> > Signed-off-by: Gerd Hoffmann <kraxel@xxxxxxxxxx> >> >> btw there's also the hyperdmabuf stuff from the xen folks, but imo their >> solution of forwarding the entire dma-buf api is over the top. This here >> looks _much_ better, pls cc all the hyperdmabuf people on your next >> version. > > Fun fact: googling for "hyperdmabuf" found me your mail and nothing else :-o > (Trying "hyper dmabuf" instead worked better then). > > Yes, will cc them on the next version. Not sure it'll help much on xen > though due to the memory management being very different. Basically xen > owns the memory, not the kernel of the control domain (dom0), so > creating dmabufs for guest memory chunks isn't that simple ... > > Also it's not clear whenever they really need guest -> guest exports or > guest -> dom0 exports. > >> Overall I like the idea, but too lazy to review. > > Cool. General comments on the idea was all I was looking for for the > moment. Spare yor review cycles for the next version ;) > >> Oh, some kselftests for this stuff would be lovely. > > I'll look into it. > > thanks, > Gerd > > _______________________________________________ > dri-devel mailing list > dri-devel@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/dri-devel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch
