[PATCH 1/3] drm/radeon: stop poisoning the GART TLB

[Christian König]

Am 19.06.2014 03:48, schrieb Michel Dänzer:
> On 15.06.2014 21:48, Christian König wrote:
>> Am 13.06.2014 23:31, schrieb Alex Deucher:
>>> On Fri, Jun 13, 2014 at 11:45 AM, Christian König
>>> <deathsimple at vodafone.de> wrote:
>>>> Hi Marek,
>>>>
>>>> ah, yes! Piglit in combination with that patch can indeed crash the box.
>>>>
>>>> Going to investigate now that I can reproduce it.
>>> I wonder if it's a clockgating issue with the MC or BIF?  You might
>>> try adjusting the rdev->cg_flags (try setting it to 0) in
>>> radeon_asic.c or disabling dpm.
>> Unfortunately that was just a false alarm.
>>
>> I was just on a branch which didn't had the "stop poisoning the GART
>> TLB" patch, after applying this patch I can again let piglit run for the
>> whole night without a lockup.
>>
>> No idea what goes wrong when Marek runs piglit, but 3.15.0+"stop
>> poisoning the GART TLB"+"force_gtt" is rock solid here.
> FWIW, 3.15 doesn't survive piglit on my Bonaire either, but 3.14 is
> fine. 3.15 seems stable on Kaveri though, but I haven't tried the
> force_gtt patch on that yet.

Yeah, I think it's just me who has a stable system with 3.15 and that 
annoys me quite a bit.

No idea what's the difference. What versions of LLVM/Mesa/Piglit are you 
using for the test?

>
> There have also been a number of bug reports about stability regressions
> in 3.15 on various SI and CIK cards. It seems likely that at least some
> of those are related to this issue as well.
>
> If we can't figure out the problem soon, we probably need to revert the
> 'Use normal BOs for page tables' and dependent changes at least for 3.15.y?

I thought about this for the whole 3.15 release cycle, but decided 
against it. But what we could do is applying the attached trivial patch, 
it pins down the page tables and so pretty much reverts to the old behavior.

I think even when we revert to the old code we have a couple of unsolved 
problems with the VM support or in the driver in general where we should 
try to understand the underlying reason for it instead of applying more 
workarounds.

Going to try harder crashing my 3.15 system,
Christian.
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