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<body><span class="vcard"><a class="email" href="mailto:chris@chris-wilson.co.uk" title="Chris Wilson <chris@chris-wilson.co.uk>"> <span class="fn">Chris Wilson</span></a>
</span> changed
<a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - [CI][BAT bsw] igt@gem_* - fail - Failed assertion: !"GPU hung""
href="https://bugs.freedesktop.org/show_bug.cgi?id=108656">bug 108656</a>
<br>
<table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>What</th>
<th>Removed</th>
<th>Added</th>
</tr>
<tr>
<td style="text-align:right;">Resolution</td>
<td>---
</td>
<td>FIXED
</td>
</tr>
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<td style="text-align:right;">Status</td>
<td>REOPENED
</td>
<td>RESOLVED
</td>
</tr></table>
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<div>
<b><a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - [CI][BAT bsw] igt@gem_* - fail - Failed assertion: !"GPU hung""
href="https://bugs.freedesktop.org/show_bug.cgi?id=108656#c17">Comment # 17</a>
on <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - [CI][BAT bsw] igt@gem_* - fail - Failed assertion: !"GPU hung""
href="https://bugs.freedesktop.org/show_bug.cgi?id=108656">bug 108656</a>
from <span class="vcard"><a class="email" href="mailto:chris@chris-wilson.co.uk" title="Chris Wilson <chris@chris-wilson.co.uk>"> <span class="fn">Chris Wilson</span></a>
</span></b>
<pre>Step 2:
commit e8894267cc3325901073e8adf0a63e2dc53b6242 (HEAD -> drm-intel-next-queued,
drm-intel/for-linux-next, drm-intel/drm-intel-next-queued)
Author: Chris Wilson <<a href="mailto:chris@chris-wilson.co.uk">chris@chris-wilson.co.uk</a>>
Date: Fri Dec 7 09:02:13 2018 +0000
drm/i915: Pipeline PDP updates for Braswell
Currently we face a severe problem on Braswell that manifests as invalid
ppGTT accesses. The code tries to maintain the PDP (page directory
pointers) inside the context in two ways, direct write into the context
and a pipelined LRI update. The direct write into the context is
fundamentally racy as it is unserialised with any access (read or write)
the GPU is doing. By asserting that Braswell is not used with vGPU
(currently an unsupported platform) we can eliminate the dangerous
direct write into the context image and solely use the pipelined update.
However, the LRI of the PDP fouls up the GPU, causing it to freeze and
take out the machine with "forcewake ack timeouts". This seems possible
to workaround by preventing the GPU from sleeping (via means of
disabling the power-state management interface, i.e. forcing each ring
to remain awake) around the update. Equally, it seems an EMIT_INVALIDATE
before the LRI is sufficient to prevent the forcewake errors.
Bugzilla: <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - [CI][BAT bsw] igt@gem_* - fail - Failed assertion: !"GPU hung""
href="show_bug.cgi?id=108656">https://bugs.freedesktop.org/show_bug.cgi?id=108656</a>
References: <a class="bz_bug_link
bz_status_NEEDINFO "
title="NEEDINFO - [CI][BAT] igt@gem_ctx_create@basic-files - incomplete - *ERROR* render: timed out waiting for forcewake ack request."
href="show_bug.cgi?id=108714">https://bugs.freedesktop.org/show_bug.cgi?id=108714</a>
Signed-off-by: Chris Wilson <<a href="mailto:chris@chris-wilson.co.uk">chris@chris-wilson.co.uk</a>>
Cc: Tvrtko Ursulin <<a href="mailto:tvrtko.ursulin@intel.com">tvrtko.ursulin@intel.com</a>>
Reviewed-by: Tvrtko Ursulin <<a href="mailto:tvrtko.ursulin@intel.com">tvrtko.ursulin@intel.com</a>>
Link:
<a href="https://patchwork.freedesktop.org/patch/msgid/20181207090213.14352-3-chris@chris-wilson.co.uk">https://patchwork.freedesktop.org/patch/msgid/20181207090213.14352-3-chris@chris-wilson.co.uk</a>
Step 3: Hope for the best.</pre>
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