there is also this dmesg-warn:
https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_3648/fi-skl-guc/igt@gem_exec_flush@basic-wb-rw-default.html

[  148.092572] [drm:guc_check_log_buf_overflow] *ERROR* GuC log buffer overflow

Also, see bug 104695

Note, the issue is flip/flopping on a lot of tests.
Also,
there is dmesg-fail on a couple of runs on:
https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_3649/fi-skl-guc/igt@gem_exec_suspend@basic-s3.html

due to:
(gem_exec_suspend:2940) igt-aux-CRITICAL: Test assertion failure function sig_abort, file igt_aux.c:482:
(gem_exec_suspend:2940) igt-aux-CRITICAL: Failed assertion: !"GPU hung"
Subtest basic-S3 failed.

(In reply to Marta Löfstedt from comment #3)
> Note, the issue is flip/flopping on a lot of tests.
> Also,
> there is dmesg-fail on a couple of runs on:
> https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_3649/fi-skl-guc/
> igt@gem_exec_suspend@basic-s3.html
> 
> due to:
> (gem_exec_suspend:2940) igt-aux-CRITICAL: Test assertion failure function
> sig_abort, file igt_aux.c:482:
> (gem_exec_suspend:2940) igt-aux-CRITICAL: Failed assertion: !"GPU hung"
> Subtest basic-S3 failed.

The GPU hang should be a different beast and should have its own bug (QA already filed a lot of these since they were validating known broken configrations).

(In reply to Chris Wilson from comment #4)
> (In reply to Marta Löfstedt from comment #3)
> > Note, the issue is flip/flopping on a lot of tests.
> > Also,
> > there is dmesg-fail on a couple of runs on:
> > https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_3649/fi-skl-guc/
> > igt@gem_exec_suspend@basic-s3.html
> > 
> > due to:
> > (gem_exec_suspend:2940) igt-aux-CRITICAL: Test assertion failure function
> > sig_abort, file igt_aux.c:482:
> > (gem_exec_suspend:2940) igt-aux-CRITICAL: Failed assertion: !"GPU hung"
> > Subtest basic-S3 failed.
> 
> The GPU hang should be a different beast and should have its own bug (QA
> already filed a lot of these since they were validating known broken
> configrations).

OK, here you go Chris, bug 104699.
I will manually add it to cibuglog although the issue is already covered by this bug.

commit bd724318b682587ad2f989ab8e0f7b3d4486ced5
Author: Michal Wajdeczko <michal.wajdeczko@intel.com>
Date:   Fri Jan 19 12:49:26 2018 +0000

    drm/i915/guc: Keep GuC log disabled by default
    
    It looks that GuC log functionality is not fully functional yet and
    causes issues when enabled by auto(-1) modparam on debug builds.
    For example, but not limited to:
    
    [   30.062893] ======================================================
    [   30.062894] WARNING: possible circular locking dependency detected
    [   30.062895] 4.15.0-rc8-CI-CI_DRM_3648+ #1 Tainted: G     U
    [   30.062896] ------------------------------------------------------
    [   30.062897] debugfs_test/1268 is trying to acquire lock:
    [   30.062898]  (&dev->struct_mutex){+.+.}, at: [<00000000e4213449>] i915_mutex_lock_interruptible+0x47/0x130 [i915]
    [   30.062921]
                   but task is already holding lock:
    [   30.062921]  (&mm->mmap_sem){++++}, at: [<00000000dd7adc93>] __do_page_fault+0x106/0x560
    [   30.062924]
                   which lock already depends on the new lock.
    
    References: 0ed87953532652 ("drm/i915/guc: Redefine guc_log_level modparam values")
    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104693
    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104694
    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104695
    Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
    Cc: Chris Wilson <chris@chris-wilson.co.uk>
    Cc: Jani Saarinen <jani.saarinen@intel.com>
    Cc: Tomi Sarvela <tomi.p.sarvela@intel.com>
    Cc: Marta Lofstedt <marta.lofstedt@intel.com>
    Cc: Michal Winiarski <michal.winiarski@intel.com>
    Link: https://patchwork.freedesktop.org/patch/msgid/20180119124926.29844-1-michal.wajdeczko@intel.com
    Reviewed-by: Michal Winiarski <michal.winiarski@intel.com>
    Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

This fix is hiding the issue since CI_DRM_3662. I can't close the bug, since I know that the issue is still there. However, I will archive from cibuglog.

Can this be closed now?