[Intel-gfx] [PATCH 2/4] drm/i915/perf: Whitelist OA report trigger registers

[Chris Wilson]

Quoting Lionel Landwerlin (2020-07-24 11:07:18)
> On 24/07/2020 12:26, Chris Wilson wrote:
> > Quoting Umesh Nerlige Ramappa (2020-07-24 01:18:59)
> >> diff --git a/drivers/gpu/drm/i915/gt/selftest_workarounds.c b/drivers/gpu/drm/i915/gt/selftest_workarounds.c
> >> index febc9e6692ba..3b1d3dbcd477 100644
> >> --- a/drivers/gpu/drm/i915/gt/selftest_workarounds.c
> >> +++ b/drivers/gpu/drm/i915/gt/selftest_workarounds.c
> >> @@ -934,6 +934,10 @@ static bool pardon_reg(struct drm_i915_private *i915, i915_reg_t reg)
> >>          static const struct regmask pardon[] = {
> >>                  { GEN9_CTX_PREEMPT_REG, INTEL_GEN_MASK(9, 9) },
> >>                  { GEN8_L3SQCREG4, INTEL_GEN_MASK(9, 9) },
> >> +               { OAREPORTTRIG2, INTEL_GEN_MASK(8, 11) },
> >> +               { OAREPORTTRIG6, INTEL_GEN_MASK(8, 11) },
> >> +               { GEN12_OAG_OAREPORTTRIG2, INTEL_GEN_MASK(12, 12) },
> >> +               { GEN12_OAG_OAREPORTTRIG6, INTEL_GEN_MASK(12, 12) },
> > Because we are not making the mistake of exposing more globals, and the
> > pardon is a list of our past sins, not an excuse for more.
> 
> I'm afraid the HW design leave us no choice on Gen12 :(

The question then is how much mischief can a client get up to if they
subvert the OA of the privileged user. It's a privilege escalation hole,
but is there anything dangerous behind it? Or is it just going to disturb
the data being fed to the privileged client... (Which seems scary enough.)
-Chris
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