Created attachment 115241 [details]
dmesg info

==System Environment==       
-----------------------------------------------------
Regression: Yes
Non-working platforms: SNB IVB

==Kernel==
--------------------------------------------------
commit b9fe357740009b89d4bac30b297bfe9808957e6a
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Mon Apr 20 10:28:37 2015 -0700

    drm-intel-nightly: 2015y-04m-20d-17h-28m-16s UTC integration manifest


==Bug detailed description==
--------------------------------------------------
igt/kms_pipe_crc_basic subcase bad-pipe causes WARNING: CPU: 0 PID: 4666 at drivers/gpu/drm/i915/i915_gem_execbuffer.c:1256 i915_gem_ringbuffer_submission+0x2a9/0x86f [i915]()

By bisected, shows the first bad commit is 5c5f645
commit 5c5f645773b6d147bf68c350674dc3ef4f8de83d
Author:     Daniel Vetter <daniel.vetter@ffwll.ch>
AuthorDate: Tue Apr 14 17:35:14 2015 +0200
Commit:     Daniel Vetter <daniel.vetter@ffwll.ch>
CommitDate: Mon Apr 20 08:55:19 2015 -0700

    drm/i915: Unify aliasing ppgtt handling
    
    With the dynamic pagetable alloc code aliasing ppgtt special-cases
    where again mixed in all over the place with the low-level init code.
    
    Extract the va preallocation and clearing again into the common code
    where aliasing ppgtt gets set up.
    
    Note that with this we don't set the size of the aliasing ppgtt to the
    size of the parent ggtt address space. Which isn't required at all
    since except for the ppgtt setup/cleanup code no one ever looks at
    this.
    
    Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
    Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>



--output dmesg info--
---------------------------------------------------------------------------
[  119.963715] ------------[ cut here ]------------
[  119.963732] WARNING: CPU: 2 PID: 5428 at drivers/gpu/drm/i915/i915_gem_execbuffer.c:1256 i915_gem_ringbuffer_submission+0x2a9/0x86f [i915]()
[  119.963734] render ring didn't clear reload
[  119.963735] Modules linked in: ipv6 dm_mod snd_hda_codec_hdmi iTCO_wdt iTCO_vendor_support ppdev snd_hda_codec_realtek snd_hda_codec_generic firewire_ohci serio_raw i2c_i801 pcspkr joydev firewire_core crc_itu_t snd_hda_intel snd_hda_controller snd_hda_codec snd_hda_core snd_hwdep snd_pcm lpc_ich mfd_core snd_timer snd soundcore parport_pc parport tpm_tis tpm acpi_cpufreq i915 button video drm_kms_helper drm
[  119.963753] CPU: 2 PID: 5428 Comm: pm_rpm Tainted: G        W       4.0.0_drm-intel-nightly_b9fe35_20150421+ #368
[  119.963755] Hardware name:                  /DQ67SW, BIOS SWQ6710H.86A.0060.2011.1220.1805 12/20/2011
[  119.963756]  0000000000000000 0000000000000009 ffffffff81795847 ffff8802300fbbb8
[  119.963759]  ffffffff8103bd5a ffff880234ac60e8 ffffffffa0096618 ffff880234ac6000
[  119.963761]  ffff88022f701c98 0000000000000000 ffff8802300fbe18 ffff88022f700000
[  119.963763] Call Trace:
[  119.963768]  [<ffffffff81795847>] ? dump_stack+0x40/0x50
[  119.963772]  [<ffffffff8103bd5a>] ? warn_slowpath_common+0x98/0xb0
[  119.963782]  [<ffffffffa0096618>] ? i915_gem_ringbuffer_submission+0x2a9/0x86f [i915]
[  119.963791]  [<ffffffff8103bdb7>] ? warn_slowpath_fmt+0x45/0x4a
[  119.963801]  [<ffffffffa0096618>] ? i915_gem_ringbuffer_submission+0x2a9/0x86f [i915]
[  119.963811]  [<ffffffffa0095ff0>] ? i915_gem_do_execbuffer.isra.13+0xca6/0xd88 [i915]
[  119.963823]  [<ffffffffa00a138a>] ? i915_gem_pwrite_ioctl+0x75a/0x7e0 [i915]
[  119.963827]  [<ffffffff8110948a>] ? __kmalloc+0x65/0x13d
[  119.963836]  [<ffffffffa0097085>] ? i915_gem_execbuffer2+0x16e/0x205 [i915]
[  119.963843]  [<ffffffffa00047ae>] ? drm_ioctl+0x322/0x38d [drm]
[  119.963852]  [<ffffffffa0096f17>] ? i915_gem_execbuffer+0x339/0x339 [i915]
[  119.963855]  [<ffffffff811207a8>] ? dput+0x24/0x1aa
[  119.963858]  [<ffffffff8111daa6>] ? do_vfs_ioctl+0x360/0x424
[  119.963861]  [<ffffffff8104fad2>] ? task_work_run+0x84/0x96
[  119.963863]  [<ffffffff8111dbb3>] ? SyS_ioctl+0x49/0x7a
[  119.963866]  [<ffffffff8179b329>] ? int_signal+0x12/0x17
[  119.963868]  [<ffffffff8179b0f2>] ? system_call_fastpath+0x12/0x17
[  119.963870] ---[ end trace e93159cda1ab216a ]---

==Reproduce steps==
----------------------------

1, ./kms_pipe_crc_basic --run-subtest bad-pipe