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<base href="https://bugs.freedesktop.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - i965 miptree MCS aux_buf allocation failure with old kernels"
href="https://bugs.freedesktop.org/show_bug.cgi?id=110602">110602</a>
</td>
</tr>
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<th>Summary</th>
<td>i965 miptree MCS aux_buf allocation failure with old kernels
</td>
</tr>
<tr>
<th>Product</th>
<td>Mesa
</td>
</tr>
<tr>
<th>Version</th>
<td>git
</td>
</tr>
<tr>
<th>Hardware</th>
<td>All
</td>
</tr>
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<th>OS</th>
<td>Linux (All)
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>medium
</td>
</tr>
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<th>Component</th>
<td>Drivers/DRI/i965
</td>
</tr>
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<th>Assignee</th>
<td>intel-3d-bugs@lists.freedesktop.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>anssi.hannula@bitwise.fi
</td>
</tr>
<tr>
<th>QA Contact</th>
<td>intel-3d-bugs@lists.freedesktop.org
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=144147" name="attach_144147" title="glxinfo">attachment 144147</a> <a href="attachment.cgi?id=144147&action=edit" title="glxinfo">[details]</a></span>
glxinfo
intel_miptree_choose_aux_usage() selects ISL_AUX_USAGE_MCS if
intel_miptree_supports_mcs() returns true.
This will cause callchain intel_miptree_alloc_aux() => intel_alloc_aux_buffer()
=> brw_bo_map(x,y,MAP_RAW|MAP_WRITE) => brw_bo_map_wc(), which checks
bufmgr->has_mmap_wc and returns NULL on !bufmgr->has_mmap_wc. There is no
fallback in brw_bo_map() for the MAP_RAW case.
This will cause intel_miptree_create() to fail which causes
intel_miptree_create_for_renderbuffer() to fail.
I guess either either the miptree creation should be retried without MCS or
intel_miptree_supports_mcs() should detect the missing mmap_wc support and
return false.
Attached is a quick hack patch that adds mmap_wc check in
intel_miptree_supports_mcs(), and it seems to fix the testcase I used
(mesa-issue-qt3d.cc).
Without the patch the testcase either crashes (git master) or flashes rapidly
(git master + two patches from <a class="bz_bug_link
bz_status_NEW "
title="NEW - i965 renderbuffer miptree creation failure not properly handled"
href="show_bug.cgi?id=110601">bug #110601</a> to workaround the crashes).
The testcase mesa-issue-qt3d.cc is also attached, plus an apitrace and glxinfo
with git master.
This was tested on a ValleyView Gen7 (8086:0f31) with kernel 3.10.35.</pre>
</div>
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