Created attachment 139317 [details]
dmesg output

Created attachment 139318 [details]
xrandr output

It appears that 5s after queuing the initial requests, we haven't even submitted them to HW. Quite distressing!

I see you are running with tip, could you please enable CONFIG_DRM_I915_TRACE_GEM=y and apply something like:

diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
index df234dc23274..6207bc35a53d 100644
--- a/drivers/gpu/drm/i915/i915_gpu_error.c
+++ b/drivers/gpu/drm/i915/i915_gpu_error.c
@@ -1840,6 +1840,8 @@ void i915_capture_error_state(struct drm_i915_private *i915,
                return;
        }
 
+       GEM_TRACE_DUMP();
+
        i915_error_capture_msg(i915, error, engine_mask, error_msg);
        DRM_INFO("%s\n", error->error_msg);

Also drm.debug=0xf (everything!) may help try to determine the delay.

Created attachment 139332 [details]
netconsole

Kernel panic, so i had to do netconsole.

Created attachment 139335 [details]
netconsole1

sorry, i added drm.debug

It should have dumped the trace to netconsole as well. Could you check the console settings?

So it appears that we wake with a ending CS interrupt before we do anything, or that the CS interrupt is too early. Common suspect in this case is IOMMU, could you try intel_iommu=igfx_off?

Created attachment 139336 [details]
netconsole

When i turned CONFIG_DRM_I915_TRACE_GEM, it on different path. So its not calling  GEM_TRACE_DUMP().
I guess now its calling GEM_BUG_ON(), and not i915_capture_error_state().

GEM_BUG_ON() includes a GEM_TRACE_DUMP; I expect it to show up here :)

Another quick test is:

diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 9f3cce022b2d..ff179c967e2a 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -1738,6 +1738,8 @@ static void enable_execlists(struct intel_engine_cs *engine)
                   engine->status_page.ggtt_offset);
        POSTING_READ(RING_HWS_PGA(engine->mmio_base));
 
+       clear_gtiir(engine);
+
        /* Following the reset, we need to reload the CSB read/write pointers */
        engine->execlists.csb_head = -1;
 }

Created attachment 139340 [details]
netconsole

With line added. I guess ftrace works now.

In the intel_iommu=igfx_off test, we got

[    0.000000] Linux version 4.17.0-rc3+ (root@amd1.blue.org) (gcc version 7.3.0 (GCC)) #5 SMP PREEMPT Fri May 4 08:44:22 CEST 2018
[    0.000000] Command line: \\k.efi rw drm.debug=0xf intel_iommu=igfx_off initrd=\i.img
...
[    0.258015] DMAR: No ATSR found
[    0.258097] DMAR: dmar0: Using Queued invalidation
[    0.258107] DMAR: dmar1: Using Queued invalidation
[    0.258195] DMAR: Setting RMRR:
[    0.258282] DMAR: Setting identity map for device 0000:00:02.0 [0x5f800000 - 0x7fffffff]
...
[  207.804629] [drm] VT-d active for gfx access

Odd. So we didn't succeed in disabling iommu. Do you mind compiling out iommu entirely to be sure we don't have a problem here with iommu+HWSP?

Created attachment 139341 [details]
netconsole take 4

Now its a bit different.

Can you please try re-enabling iommu and https://patchwork.freedesktop.org/patch/221513/ ?

(In reply to Chris Wilson from comment #14)
> Can you please try re-enabling iommu and
> https://patchwork.freedesktop.org/patch/221513/ ?

No it doesnt help, 
GPU HANG: ecode 9:0:0xfffffffe, reason: hang on rcs0, bcs0, vcs0, vecs0, action: reset

Do you need debug enabled and console output ?
If you have any other ideas or extra debug flags let me know.

Created attachment 139587 [details]
dmesg output

tried on latest drm-tip

Yes, please send dmesg with drm.debug=0x1e log_buf_len=4M.

Created attachment 139590 [details]
dmesg

used drm.debug=0x1e log_buf_len=4M

Chris, any updates on this issue?

Domen, are you still experiencing this issue?

Having purchased a glk (celeron N4100) for myself... This looks like to be an isolated incident (well this and the other glk-iommu reported issues!), as annoyingly it worksforme. I was hoping to able to reproduce, sorry.

Sorry, we dont use this board anymore. So i dont know if issue still persits.

Apologies for the disappointing end.