Dave Gordon <david.s.gordon@xxxxxxxxx> writes: > On 10/06/15 12:42, Michel Thierry wrote: >> On 5/29/2015 1:53 PM, Michel Thierry wrote: >>> On 5/29/2015 12:05 PM, Michel Thierry wrote: >>>> On 5/22/2015 6:04 PM, Mika Kuoppala wrote: >>>>> With BDW/SKL and 32bit addressing mode only, the hardware preloads >>>>> pdps. However the TLB invalidation only has effect on levels below >>>>> the pdps. This means that if pdps change, hw might access with >>>>> stale pdp entry. >>>>> >>>>> To combat this problem, preallocate the top pdps so that hw sees >>>>> them as immutable for each context. >>>>> >>>>> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> >>>>> Cc: Rafael Barbalho <rafael.barbalho@xxxxxxxxx> >>>>> Signed-off-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxx> >>>>> --- >>>>> drivers/gpu/drm/i915/i915_gem_gtt.c | 50 >>>>> +++++++++++++++++++++++++++++++++++++ >>>>> drivers/gpu/drm/i915/i915_reg.h | 17 +++++++++++++ >>>>> drivers/gpu/drm/i915/intel_lrc.c | 15 +---------- >>>>> 3 files changed, 68 insertions(+), 14 deletions(-) >>>>> >>>>> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c >>>>> b/drivers/gpu/drm/i915/i915_gem_gtt.c >>>>> index 0ffd459..1a5ad4c 100644 >>>>> --- a/drivers/gpu/drm/i915/i915_gem_gtt.c >>>>> +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c >>>>> @@ -941,6 +941,48 @@ err_out: >>>>> return ret; >>>>> } >>>>> >>>>> +/* With some architectures and 32bit legacy mode, hardware pre-loads >>>>> the >>>>> + * top level pdps but the tlb invalidation only invalidates the >>>>> lower levels. >>>>> + * This might lead to hw fetching with stale pdp entries if top level >>>>> + * structure changes, ie va space grows with dynamic page tables. >>>>> + */ > > Is this still necessary if we reload PDPs via LRI instructions whenever > the address map has changed? That always (AFAICT) causes sufficient > invalidation, so then we might not need to preallocate at all :) > LRI reload gets my vote. Please ignore this patch. -Mika > .Dave. _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
