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<body><span class="vcard"><a class="email" href="mailto:kenneth@whitecape.org" title="Kenneth Graunke <kenneth@whitecape.org>"> <span class="fn">Kenneth Graunke</span></a>
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<a class="bz_bug_link
bz_status_NEW "
title="NEW - [BDW] [Bisected] Absolute constant buffers break VAAPI in mpv"
href="https://bugs.freedesktop.org/show_bug.cgi?id=102774">bug 102774</a>
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<td>chris@chris-wilson.co.uk, daniel@ffwll.ch
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<b><a class="bz_bug_link
bz_status_NEW "
title="NEW - [BDW] [Bisected] Absolute constant buffers break VAAPI in mpv"
href="https://bugs.freedesktop.org/show_bug.cgi?id=102774#c14">Comment # 14</a>
on <a class="bz_bug_link
bz_status_NEW "
title="NEW - [BDW] [Bisected] Absolute constant buffers break VAAPI in mpv"
href="https://bugs.freedesktop.org/show_bug.cgi?id=102774">bug 102774</a>
from <span class="vcard"><a class="email" href="mailto:kenneth@whitecape.org" title="Kenneth Graunke <kenneth@whitecape.org>"> <span class="fn">Kenneth Graunke</span></a>
</span></b>
<pre>Daniel reminded me that X (Glamor) and GNOME Shell use Mesa, so my earlier
testing wasn't completely on Mesa 17.1. I can now confirm the report (on
Kabylake).
mpv -hwdec=vaapi -vo=vaapi did indeed work with Mesa 17.1. It misrenders or
GPU hangs with 17.2 and later (due to "i965: Switch to absolute addressing for
constant buffer 0").
I ran a few more experiments:
- Starting X/Glamor with 17.1 without a compositor...
- mpv -hwdec=vaapi -vo=vaapi appears to work with any Mesa version
- Running Piglit using Mesa 17.2+ concurrently with a working mpv works
fine...both mpv and Piglit work fine.
I think this suggests that CS_DEBUG_MODE2 is indeed saved and restored as part
of the context - Glamor and mpv (on 17.1) would expect relative mode, and
Piglit (on 17.2+) would expect absolute mode. And both worked. Daniel had
suggested there might be a bug where setting the mode made it take effect on
all rings, and that seems to not be the case either.
- Starting X/Glamor with 17.2+ without a compositor...
- mpv -hwdec=vaapi -vo=vaapi misrenders and GPU hangs.
My theory is that new contexts are inheriting the state from X/Glamor's
context. I'd say maybe it's because it gets the fd from X via DRI3...but that
doesn't make much sense, because libva-intel-driver doesn't use DRI3. Maybe
it's because X is the first client on the system? Or it's drm master? Or runs
just before mpv?
Note that libva-intel-driver doesn't create its own context. But I think the
kernel ought to make one for it, when it opens the fd...
Daniel, Chris, do you have any ideas?</pre>
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