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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 - X server crashes in i965 on desktop startup when DRI3 v1.2 / modifier support is enabled"
href="https://bugs.freedesktop.org/show_bug.cgi?id=106642">106642</a>
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<th>Summary</th>
<td>X server crashes in i965 on desktop startup when DRI3 v1.2 / modifier support is enabled
</td>
</tr>
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<th>Product</th>
<td>Mesa
</td>
</tr>
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<th>Version</th>
<td>git
</td>
</tr>
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<th>Hardware</th>
<td>Other
</td>
</tr>
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<th>OS</th>
<td>All
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Keywords</th>
<td>regression
</td>
</tr>
<tr>
<th>Severity</th>
<td>blocker
</td>
</tr>
<tr>
<th>Priority</th>
<td>highest
</td>
</tr>
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<th>Component</th>
<td>Drivers/DRI/i965
</td>
</tr>
<tr>
<th>Assignee</th>
<td>intel-3d-bugs@lists.freedesktop.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>eero.t.tamminen@intel.com
</td>
</tr>
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<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=139737" name="attach_139737" title="Gdb backtrace of the X server crash">attachment 139737</a> <a href="attachment.cgi?id=139737&action=edit" title="Gdb backtrace of the X server crash">[details]</a></span>
Gdb backtrace of the X server crash
Setup:
* drm-tip kernel
* Mesa git from last night
* X server v1.20 or newer, with DRI3 v1.2 / modifiers enabled in X
configuration:
------------------------
Section "ServerFlags"
Option "Debug" "dmabuf_capable"
EndSection
------------------------
* Rest is Ubuntu 16.04
Use-case:
* Log in to X session that uses GL/GLES compositor (Unity, Gnome...)
Expected result:
* Desktop appears
Actual result:
* X crashes in i965 driver, on all devices we have
Crash disappears if one disables the X configuration "dmabuf_capable" setting
that enables DRI3 v1.2 / modifiers support in X.
Crash is here:
Thread 1 "X" received signal SIGSEGV, Segmentation fault.
0x00007f19d6d487ca in isl_format_supports_ccs_e
(devinfo=devinfo@entry=0x2286ab8, format=ISL_FORMAT_UNSUPPORTED)
at isl/isl_format.c:558
See attached Gdb backtrace for more info.
Looking at the indicated code, the bug is obvious:
* isl.h declares:
ISL_FORMAT_UNSUPPORTED = UINT16_MAX
* isl_format_supports_ccs_e() function uses that as array index:
-------------------------------
isl_format_supports_ccs_e(const struct gen_device_info *devinfo,
enum isl_format format)
{
if (!format_info[format].exists)
return false;
...
-------------------------------
* But array size is much smaller:
$ grep " SF" ./src/intel/isl/isl_format.c | wc -l
258
Crash started to happen between:
* 2018-05-22 17:02:28 UTC: 92f01fc5f9: i965: Emit VF cache invalidates for
48-bit addressing bugs with softpin.
* 2018-05-23 17:19:04 UTC: b73b340c37: i965: add {X,A}BGR2101010 to
'intel_image_formats'
Either addition of the new formats, or Jason's blitter support removal commits
started to trigger usage of ISL_FORMAT_UNSUPPORTED.</pre>
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