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

[Christian König]

Am 23.06.2014 10:15, schrieb Michel Dänzer:
> On 19.06.2014 18:45, Christian König wrote:
>> Am 19.06.2014 03:48, schrieb Michel Dänzer:
>>> On 15.06.2014 21:48, Christian König wrote:
>>>> 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.
> FWIW though, my Kaveri doesn't always survive piglit either, e.g. this
> morning it didn't once again, then did after a reboot. (That's using
> SDMA; Kaveri was never switched back to CPDMA)
>
>
>> No idea what's the difference. What versions of LLVM/Mesa/Piglit are you
>> using for the test?
> Current Git of everything.
>
>
>>> 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.
> This patch applied on top of 3.15 + stop poisoning the GART TLB doesn't
> seem to help on my Bonaire, unfortunately.

That's unfortunately what I already expected. Making the page tables 
movable isn't really the cause of the problem, it must be rather 
something else which is a bit more subtle. Like incorrect aligning 
somewhere or something like this.

>
>> 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.
> I'm not suggesting applying more workarounds but going back to a known
> more stable state. It seems like we've maneuvered ourselves to a rather
> uncomfortable position from there, with no clear way to a better place.
> But if we basically started from the 3.14 state again, we have a few
> known hurdles like mine and Marek's Bonaire etc. which we know any
> further improvements will have to pass before they can be considered for
> general consumption.

Yeah agree, especially on the uncomfortable position.

Please try with the two attached patches applied on top of 3.15 and 
retest. They should revert back to the old implementation.

Thanks for the help,
Christian.
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