On Tue, Sep 09, 2014 at 04:30:06PM +0300, Ville Syrjälä wrote: > On Tue, Sep 09, 2014 at 02:07:24PM +0100, Chris Wilson wrote: > > On Tue, Sep 09, 2014 at 12:41:34PM +0000, Thierry, Michel wrote: > > > > > > > > > On Tue, Sep 9, 2014 at 1:34 PM, Ville Syrjälä > > > <ville.syrjala@xxxxxxxxxxxxxxx> wrote: > > > > On Tue, Sep 09, 2014 at 12:57:11PM +0100, Chris Wilson wrote: > > > > > On Fri, Sep 05, 2014 at 02:13:16PM +0100, Michel Thierry wrote: > > > > > > Use full PPGTT as the default option in gen7. > > > > > > Note that aliasing PPGTT is the default option for gen8 (see > > > HAS_PPGTT). > > > > > > > > > > > > This may well come back to bite me later. > > > > > > > > > > Indeed. So something I spotted was that bspec mentions that the per-ring > > > > > PDE registers (RING_PP_DIR_DCLV and RING_PP_DIR_BASE) are stored in > > > > the > > > > > logical context and so the registers are restored along with the > > > > > context. If this is correct what happens when we switch logical contexts > > > > > on RCS whilst we have active work on BCS etc? Does this mean that we > > > > > have to serialise context switches across rings, or is my reading of the > > > > > bspec false? > > > > > > > > How does rcs PP_DIR_* affect bcs? Also IIRC that stuff is part of > > > > the execlist context which isn't saved/restored unless execlists > > > > are actually enabled. IIRC when I tried it, snb did reserve the > > > > space for that stuff in the context image but didn't save/restore > > > > it, but ivb+ didn't even reserve the space. > > > > > > > Yes, my understanding is that these registers are per engine, and bcs > > > couldn't be affected by rcs. > > > > They are per-engine, but are they stored in the logical context (which > > is what bspec says afaict) and so reloaded with the wrong values when > > RCS executes MI_SET_CONTEXT? That is the question. > > I don't see any !RCS PP_DIR_* registers listed in the execlist context. > Also BSpec says that RCS PP_DIR_* registers are stored in the power context > rather than the execlist context in ring buffer mode. BSpec is a bit thin > on what happens to these registers on other engines eg. during rc6. I guess > they must have their own power contexts. Cool. I was read an old copy of the bspec offline, so hopefully I can just blame it on early cut'n'pasting. I wrote igt/gem_ppgtt to try and race MI_SET_CONTEXT against a BCS workload and that seems fairly convincing that the PP_DIR registers are unaffected by the context restore. Oh, wait. It just uses the default-context on each fd, i.e. doesn't actually perform the context restores. Will check back later... -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
