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

[Lionel Landwerlin]

On 24/07/2020 13:23, Chris Wilson wrote:
> Quoting Chris Wilson (2020-07-24 11:19:05)
>> 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.)
> The other angle is whether the RING_NONPRIV are context saved; I have
> vague memories of seeing them in the context image. If they are, we can
> add them the to privileged OA client. We still need to respect the
> hard limit on the number, but that would close the hole.
> -Chris

I couldn't find how to do this whitelisting per context. If that's 
possible, that's probably what we should do.


-Lionel