Following up on bug 1680505 comment 17: turns out we already had almost everything in place to reliably detect the right device and vendor id - at least on mesa drivers. This makes our detection much more reliable in multi-gpu cases and should bring it on par again with what we had when using GLX.

In D98108 we added infrastructure to detect infos for DRM devices in
multi GPU setups. We didn't use it for detecting device and vendor IDs
thought, which remained flaky.

Extend the code a little bit, allowing us to reliably get the right
IDs - at least for mesa drivers. This should make our detection
as reliable as it was when using GLX.

https://treeherder.mozilla.org/jobs?repo=try&revision=81dc1201ecbd5ed06b25a5d071c7c036032e8b73

https://treeherder.mozilla.org/jobs?repo=try&revision=ce6029aeb2b41e8fd5dad0bcae8f8e6529093d48

https://hg.mozilla.org/mozilla-central/rev/035499c85eb9

We should consider backporting this in a couple of days if no regressions are reported - it moves a bunch of systems from SW-WR to HW-WR and silences an annoying warning that gets reported in many bug reports (usually unrelated).

(Martin Stránský [:stransky] (ni? me) from bug 1680505 comment 9)

To be clear here - WebRender HW is disabled by default on 2 GPU system but when I enable it at about:config it works as expected.

Can you confirm that both GPUs are now correctly detected and that WebRender is no longer disabled by default?

Seems to be working, Thanks.

Comment on attachment 9230788 [details]
Bug 1720187 - Better device and vendor ID detection in glxtest, r=aosmond

Beta/Release Uplift Approval Request

• User impact if declined: Some users won't get hardware Webrender and annoying error messages in about:support.
• Is this code covered by automated tests?: No
• Has the fix been verified in Nightly?: Yes
• Needs manual test from QE?: No
• If yes, steps to reproduce:
• List of other uplifts needed: None
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): The worst case would be that other users now don't get hardware WR. There haven't been any reports for that yet and the patch has been tested on a variety of setups.
• String changes made/needed:

Comment on attachment 9230788 [details]
Bug 1720187 - Better device and vendor ID detection in glxtest, r=aosmond

Approved for 91 beta 6, thanks.

https://hg.mozilla.org/releases/mozilla-beta/rev/10821c4f8a77