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<body><span class="vcard"><a class="email" href="mailto:lakshminarayana.vudum@intel.com" title="Lakshmi <lakshminarayana.vudum@intel.com>"> <span class="fn">Lakshmi</span></a>
</span> changed
<a class="bz_bug_link
bz_status_CLOSED bz_closed"
title="CLOSED 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>
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<th>What</th>
<th>Removed</th>
<th>Added</th>
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<td style="text-align:right;">Status</td>
<td>RESOLVED
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<td>CLOSED
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<b><a class="bz_bug_link
bz_status_CLOSED bz_closed"
title="CLOSED 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#c17">Comment # 17</a>
on <a class="bz_bug_link
bz_status_CLOSED bz_closed"
title="CLOSED 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:lakshminarayana.vudum@intel.com" title="Lakshmi <lakshminarayana.vudum@intel.com>"> <span class="fn">Lakshmi</span></a>
</span></b>
<pre>(In reply to Chris Wilson from <a href="show_bug.cgi?id=104708#c16">comment #16</a>)
<span class="quote">> 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">https://patchwork.freedesktop.org/patch/msgid/20180511121147.31915-1</a>-
> <a href="mailto:chris@chris-wilson.co.uk">chris@chris-wilson.co.uk</a></span >
Closing this issue as this was already resolved and verified.</pre>
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