[Intel-gfx] [PATCH 6/6] drm/i915/gt: Always poison the kernel_context image before unparking

[Chris Wilson]

Quoting Mika Kuoppala (2019-12-30 16:23:20)
> Chris Wilson <chris at chris-wilson.co.uk> writes:
> 
> > Keep scrubbing the kernel_context image with poison before we reset it
> > in order to demonstrate that we will be resilient in the case where it
> > is accidentally overwritten on idle.
> >
> > Suggested-by: Imre Deak <imre.deak at intel.com>
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Imre Deak <imre.deak at intel.com>
> > ---
> >  drivers/gpu/drm/i915/gt/intel_context_types.h |  2 ++
> >  drivers/gpu/drm/i915/gt/intel_engine_pm.c     | 18 +++++++++++++++++-
> >  drivers/gpu/drm/i915/gt/intel_lrc.c           |  4 ++--
> >  3 files changed, 21 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gt/intel_context_types.h b/drivers/gpu/drm/i915/gt/intel_context_types.h
> > index 9527a659546c..ca1420fb8b53 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_context_types.h
> > +++ b/drivers/gpu/drm/i915/gt/intel_context_types.h
> > @@ -17,6 +17,8 @@
> >  #include "intel_engine_types.h"
> >  #include "intel_sseu.h"
> >  
> > +#define CONTEXT_REDZONE POISON_INUSE
> > +
> >  struct i915_gem_context;
> >  struct i915_vma;
> >  struct intel_context;
> > diff --git a/drivers/gpu/drm/i915/gt/intel_engine_pm.c b/drivers/gpu/drm/i915/gt/intel_engine_pm.c
> > index 1b9f73948f22..ea90ab3e396e 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_engine_pm.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_engine_pm.c
> > @@ -37,8 +37,24 @@ static int __engine_unpark(struct intel_wakeref *wf)
> >  
> >       /* Discard stale context state from across idling */
> >       ce = engine->kernel_context;
> > -     if (ce)
> > +     if (ce) {
> > +             GEM_BUG_ON(test_bit(CONTEXT_VALID_BIT, &ce->flags));
> > +
> > +             /* First poison the image to verify we never fully trust it */
> > +             if (IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM) && ce->state) {
> > +                     struct drm_i915_gem_object *obj = ce->state->obj;
> > +                     int type = i915_coherent_map_type(engine->i915);
> > +
> > +                     map = i915_gem_object_pin_map(obj, type);
> > +                     if (!IS_ERR(map)) {
> > +                             memset(map, CONTEXT_REDZONE, obj->base.size);
> 
> Just pondering if the dword granularity would suffice.

Pure debug, so convenience of memchr_inv() rules.
-Chris