Hi Tvrtko, > -----Original Message----- > From: Tvrtko Ursulin <tvrtko.ursu...@linux.intel.com> > Sent: Thursday, November 2, 2023 10:41 AM > To: Hajda, Andrzej <andrzej.ha...@intel.com>; Sripada, Radhakrishna > <radhakrishna.srip...@intel.com>; intel-gfx@lists.freedesktop.org > Cc: Chris Wilson <chris.p.wil...@linux.intel.com> > Subject: Re: [Intel-gfx] [PATCH] drm/i915/mtl: Increase guard pages when vt-d > is > enabled > > > On 02/11/2023 16:58, Andrzej Hajda wrote: > > On 02.11.2023 17:06, Radhakrishna Sripada wrote: > >> Experiments were conducted with different multipliers to VTD_GUARD macro > >> with multiplier of 185 we were observing occasional pipe faults when > >> running kms_cursor_legacy --run-subtest single-bo > >> > >> There could possibly be an underlying issue that is being > >> investigated, for > >> now bump the guard pages for MTL. > >> > >> Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/2017 > >> Cc: Gustavo Sousa <gustavo.so...@intel.com> > >> Cc: Chris Wilson <chris.p.wil...@linux.intel.com> > >> Signed-off-by: Radhakrishna Sripada <radhakrishna.srip...@intel.com> > >> --- > >> drivers/gpu/drm/i915/gem/i915_gem_domain.c | 3 +++ > >> 1 file changed, 3 insertions(+) > >> > >> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_domain.c > >> b/drivers/gpu/drm/i915/gem/i915_gem_domain.c > >> index 3770828f2eaf..b65f84c6bb3f 100644 > >> --- a/drivers/gpu/drm/i915/gem/i915_gem_domain.c > >> +++ b/drivers/gpu/drm/i915/gem/i915_gem_domain.c > >> @@ -456,6 +456,9 @@ i915_gem_object_pin_to_display_plane(struct > >> drm_i915_gem_object *obj, > >> if (intel_scanout_needs_vtd_wa(i915)) { > >> unsigned int guard = VTD_GUARD; > >> + if (IS_METEORLAKE(i915)) > >> + guard *= 200; > >> + > > > > 200 * VTD_GUARD = 200 * 168 * 4K = 131MB > > > > Looks insanely high, 131MB for padding, if this is before and after it > > becomes even 262MB of wasted address per plane. Just signalling, I do > > not know if this actually hurts. > > Yeah this feels crazy. There must be some other explanation which is > getting hidden by the crazy amount of padding so I'd rather we figured > it out. > > With 262MiB per fb how many fit in GGTT before eviction hits? N screens > with double/triple buffering?
I believe with this method we will have to limit the no of frame buffers in the system. One alternative that worked is to do a proper clear range for the ggtt instead of doing a nop. Although it adds marginal time during suspend/resume/boot it does not add restrictions to the no of fb's that can be used. > > Regards, > > Tvrtko > > P.S. Where did the 185 from the commit message come from? 185 came from experiment to increase the guard size. It is not a standard number. Regards, Radhakrishna(RK) Sripada
