On Wed, 3 Sep 2014 21:41:02 +0200 Daniel Vetter <daniel@xxxxxxxx> wrote: > On Wed, Sep 3, 2014 at 9:01 PM, Jesse Barnes <jbarnes@xxxxxxxxxxxxxxxx> wrote: > > On Wed, 3 Sep 2014 17:08:53 +0100 > > Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote: > >> On Wed, Sep 03, 2014 at 08:41:06AM -0700, Jesse Barnes wrote: > >> > On Wed, 3 Sep 2014 08:01:55 +0100 > >> > Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote: > >> > > >> > > These commands are illegal/invalid inside the object, only valid inside > >> > > the ring. > >> > > >> > Hm, we ought to be able to write to no privileged space with > >> > STORE_DWORD, but that does mean moving to context specific pages in > >> > process space, or at least adding them to our existing scheme. > >> > >> The per-process context page also doesn't exist generically. I certainly > >> hope that userspace can't overwrite the hws! Imagine if we were using > >> that for interrupt status reads, or seqno tracking... > > > > Yeah I'm thinking of an additional hws that's per-context and userspace > > mappable. It could come in handy for userspace only sync stuff. > > Userspace can already do seqno writes with MI_FLUSH_DW or PIPE_CONTROL > - lots of igt tests actually do that for correctness checks. So the > only thing really is interrupts, and I think for that we really want > the full request tracking machinery in the kernel (otherwise I fear > we'll have even more fun with lost/spurious interrupts since the hw > guys just seem to not be able to get that right). Which means a full > batch split. > > I have no idea how that's supposed to work when userspace does direct > hardware submission. But that's kinda a good reason not to do that > anyway, and at least for now it looks like direct hw submission is for > opencl2 only with interop with other devices (where sync matters) not > a use-case. For interop with other processes the gpu can always do a > seqno write to some shared page. And busy-looping, but apparently > that's what people want for low-latency. Or at least what designers > seem to think people want ... Yeah I haven't thought how direct submission will work in terms of IPC. It may just have to be done in userland with a custom cooperative mechanism... -- Jesse Barnes, Intel Open Source Technology Center _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
