[Nouveau] [Mesa-dev] Chromium - Application-level nouveau blacklist

[Stéphane Marchesin]

On Sat, Jan 5, 2019 at 11:37 PM Jason Ekstrand <jason at jlekstrand.net> wrote:
>
> On Sat, Jan 5, 2019 at 2:40 PM Ilia Mirkin <imirkin at alum.mit.edu> wrote:
>>
>> It looks like as of Chromium 71, nouveau is completely blacklisted.
>
>
> That's rather unfortunate. :-(  The intel mesa drivers were also blacklisted for quite some time a while back.  I'm not really sure what we did to get blacklisted or what we did to get unblacklisted.
>

One major difference is that we have shipped Chromebooks with
intel-based GPUs for ~8 years, so we (collectively, intel and Chrome
OS folks) have fixed the long tail of Chrome bugs for Chrome OS +
Intel, and Linux benefited as a side effect.


>>
>> I don't really see a way back from this, since they don't cite any
>> easily reproducible issues, except that some people had some issues
>> with indeterminate hardware and indeterminate versions of mesa.
>>
>> In the bug that triggered this
>> (https://bugs.chromium.org/p/chromium/issues/detail?id=876523), where
>> I might have slightly lost my cool, they (at the end) suggested that
>> we try to make nouveau a first-class citizen with chromium. However I
>> will never be able to present concrete evidence that inconcrete issues
>> are resolved. I did run the WebGL CTS suite, but that resulted in some
>> hangs from the the max-texture-size-equivalent test, and some
>> browser-level weirdness after some tests where later tests all fail
>> (due to what I have to assume is a browser bug). I don't think I
>> managed to properly track down the true reason why. I didn't want to
>> reach out to them with such results, as that's just further evidence
>> of nouveau not working perfectly.
>
>
> If you want concrete bugs to fix, I highly recommend OpenGL[ES] conformance tests, dEQP, and the WebGL CTS (which is mostly a re-hash of the OpenGL ES 3.0 CTS).  Google cares quite a bit about driver conformance and are much more likely to consider nouveau to be high-quality if those test suites are in good shape.  Years of experience dealing with Google says that dEQP results speak much louder than philosophical arguments about who should decide whether or not Chromium should accept the distro GL.  Fortunately for you, the well funded driver teams (Intel and AMD) have already done a lot of the painful work of getting a lot of the bugs and "bugs" out of core mesa and galium.  What's left are likely real back-end driver bugs which may be affecting some user somewhere so they're worth fixing.

The cause of this blacklist is not (lack of) deqp conformance, but
instead mostly automated crash reports. In other words, crashes in the
field where we have a backtrace but not necessarily a good repro case.
For someone building an application like Chrome, the multitude of
kernel+user space drivers+OS version+compositor combinations basically
makes each bug a very, very long investigation. I argued a long time
ago that we should try to get more communication going between Chrome
folks and Linux GPU driver folks to fix this, but quickly realized
that the task at hand is huge. You can only make a dent in it by being
very systematic about it. If someone wants to commit the time to do
that, I would be happy to help communication around these efforts.


>
>>
>> In the meanwhile, end users are losing accelerated WebGL which in
>> practice worked just fine (at least in my usage of it), and probably
>> some other functionality.
>>
>> One idea is to flip GL_VENDOR to some random string if chromium is
>> running. I don't like this idea, but I also don't have any great
>> alternatives. We can also just take this, as yet-another nail in the
>> nouveau coffin.
>
>
> You asked for opinions, so here you go. :-P  In my personal (and rather disinterested) opinion, I would recommend against such measures.  The last thing anyone needs is an arms race between nouveau and Chromium teams.  I think the better short-term thing to do would be to provide some documentation about WebGL and educate users about Chromium's --ignore-gpu-blacklist option.  This documentation could go on the mesa website or, likely more usefully, it could go in various distro wiki entries about nouveau and/or general nvidia issues.  In the long term, what's needed is improving nouveau quality and stability and re-building trust with the Chromium team.  I'm not trying to attack nouveau here but the fact is that trust has been lost due to an unfortunate history of mis-filed (against Chromium) bugs.  That trust doesn't get re-built by nuclear solutions.


Yes I think the Chrome-side is very simple here: because there isn't
time or means for in-depth investigation, if a driver crashes too
much, it gets blacklisted. The situation is not unique, the GPU
blacklist file is 1700 lines:
https://chromium.googlesource.com/chromium/src/gpu/+/master/config/software_rendering_list.json

Anyway, IMO if the biggest crashers can be fixed, I think we could
eventually make a case to reenable.

Stéphane

>
> --Jason
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