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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 - [IGT] igt@gem_exec_flush@* BUG: unable to handle kernel paging request at 0000000100000084"
href="https://bugs.freedesktop.org/show_bug.cgi?id=104708">bug 104708</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>
<tr>
<td style="text-align:right;">Status</td>
<td>NEW
</td>
<td>RESOLVED
</td>
</tr></table>
<p>
<div>
<b><a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - [IGT] igt@gem_exec_flush@* BUG: unable to handle kernel paging request at 0000000100000084"
href="https://bugs.freedesktop.org/show_bug.cgi?id=104708#c16">Comment # 16</a>
on <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - [IGT] igt@gem_exec_flush@* BUG: unable to handle kernel paging request at 0000000100000084"
href="https://bugs.freedesktop.org/show_bug.cgi?id=104708">bug 104708</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>commit 77dfedb5be03779f9a5d83e323a1b36e32090105
Author: Chris Wilson <<a href="mailto:chris@chris-wilson.co.uk">chris@chris-wilson.co.uk</a>>
Date: Fri May 11 13:11:45 2018 +0100
drm/i915/execlists: Use rmb() to order CSB reads
We assume that the CSB is written using the normal ringbuffer
coherency protocols, as outlined in kernel/events/ring_buffer.c:
* (HW) (DRIVER)
*
* if (LOAD ->data_tail) { LOAD ->data_head
* (A) smp_rmb() (C)
* STORE $data LOAD $data
* smp_wmb() (B) smp_mb() (D)
* STORE ->data_head STORE ->data_tail
* }
So we assume that the HW fulfils its ordering requirements (B), and so
we should use a complimentary rmb (C) to ensure that our read of its
WRITE pointer is completed before we start accessing the data.
The final mb (D) is implied by the uncached mmio we perform to inform
the HW of our READ pointer.
References: <a class="bz_bug_link
bz_status_CLOSED bz_closed"
title="CLOSED FIXED - GPU Hang with single-channel RAM configuration"
href="show_bug.cgi?id=105064">https://bugs.freedesktop.org/show_bug.cgi?id=105064</a>
References: <a class="bz_bug_link
bz_status_CLOSED bz_closed"
title="CLOSED FIXED - [CNL] System hang: GEM_BUG_ON(buf[2 * head + 1] != port->context_id) during piglit/gem_ctx_switch, masked by tracing enabled"
href="show_bug.cgi?id=105888">https://bugs.freedesktop.org/show_bug.cgi?id=105888</a>
References: <a class="bz_bug_link
bz_status_NEEDINFO "
title="NEEDINFO - [CNL-Y] GPU hang"
href="show_bug.cgi?id=106185">https://bugs.freedesktop.org/show_bug.cgi?id=106185</a>
Fixes: 767a983ab255 ("drm/i915/execlists: Read the context-status HEAD from
the HWSP")
References: 61bf9719fa17 ("drm/i915/cnl: Use mmio access to context status
buffer")
Suggested-by: Mika Kuoppala <<a href="mailto:mika.kuoppala@linux.intel.com">mika.kuoppala@linux.intel.com</a>>
Signed-off-by: Chris Wilson <<a href="mailto:chris@chris-wilson.co.uk">chris@chris-wilson.co.uk</a>>
Cc: Mika Kuoppala <<a href="mailto:mika.kuoppala@linux.intel.com">mika.kuoppala@linux.intel.com</a>>
Cc: Joonas Lahtinen <<a href="mailto:joonas.lahtinen@linux.intel.com">joonas.lahtinen@linux.intel.com</a>>
Cc: Tvrtko Ursulin <<a href="mailto:tvrtko.ursulin@intel.com">tvrtko.ursulin@intel.com</a>>
Cc: Michał Winiarski <<a href="mailto:michal.winiarski@intel.com">michal.winiarski@intel.com</a>>
Cc: Rafael Antognolli <<a href="mailto:rafael.antognolli@intel.com">rafael.antognolli@intel.com</a>>
Cc: Michel Thierry <<a href="mailto:michel.thierry@intel.com">michel.thierry@intel.com</a>>
Cc: Timo Aaltonen <<a href="mailto:tjaalton@ubuntu.com">tjaalton@ubuntu.com</a>>
Tested-by: Timo Aaltonen <<a href="mailto:tjaalton@ubuntu.com">tjaalton@ubuntu.com</a>>
Acked-by: Michel Thierry <<a href="mailto:michel.thierry@intel.com">michel.thierry@intel.com</a>>
Acked-by: Mika Kuoppala <<a href="mailto:mika.kuoppala@linux.intel.com">mika.kuoppala@linux.intel.com</a>>
Link:
<a href="https://patchwork.freedesktop.org/patch/msgid/20180511121147.31915-1-chris@chris-wilson.co.uk">https://patchwork.freedesktop.org/patch/msgid/20180511121147.31915-1-chris@chris-wilson.co.uk</a></pre>
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