Commit 4cfe4c0e authored by Sebastian Brzezinka's avatar Sebastian Brzezinka Committed by Tvrtko Ursulin
Browse files

drm/i915: skip __i915_request_skip() for already signaled requests 

After a GPU reset the HWSP is zeroed, so previously completed
requests appear incomplete. If such a request is picked up during
reset_rewind() and marked guilty, i915_request_set_error_once()
returns early (fence already signaled), leaving fence.error without
a fatal error code. The subsequent __i915_request_skip() then hits:
```
GEM_BUG_ON(!fatal_error(rq->fence.error))
```

Fixes a kernel BUG observed on Sandy Bridge (Gen6) during
heartbeat-triggered engine resets.
```
kernel BUG at drivers/gpu/drm/i915/i915_request.c:556!
RIP: __i915_request_skip+0x15e/0x1d0 [i915]
...
__i915_request_reset+0x212/0xa70 [i915]
reset_rewind+0xe4/0x280 [i915]
intel_gt_reset+0x30d/0x5b0 [i915]
heartbeat+0x516/0x530 [i915]
```

Guard __i915_request_skip() with i915_request_signaled(), if the
fence is already signaled, the ring content is committed and there
is nothing left to skip.

Fixes: 36e191f0 ("drm/i915: Apply i915_request_skip() on submission")
Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/work_items/13729


Signed-off-by: default avatarSebastian Brzezinka <sebastian.brzezinka@intel.com>
Cc: stable@vger.kernel.org # v5.7+
Reviewed-by: default avatarKrzysztof Karas <krzysztof.karas@intel.com>
Reviewed-by: default avatarAndi Shyti <andi.shyti@linux.intel.com>
Signed-off-by: default avatarAndi Shyti <andi.shyti@linux.intel.com>
Link: https://lore.kernel.org/r/fe76921d35b6ae85aa651822726d0d9815aa5362.1776339012.git.sebastian.brzezinka@intel.com


(cherry picked from commit 5ba54393dcd7adf75a9f39f5a933b1538349cad5)
Signed-off-by: default avatarTvrtko Ursulin <tursulin@ursulin.net>
parent 5d691905

drivers/gpu/drm/i915/gt/intel_reset.c

+2 −1
Original line number Diff line number Diff line
@@ -132,6 +132,7 @@ void __i915_request_reset(struct i915_request *rq, bool guilty) 
	rcu_read_lock(); /* protect the GEM context */

	if (guilty) {

		i915_request_set_error_once(rq, -EIO);

		if (!i915_request_signaled(rq))

			__i915_request_skip(rq);

		banned = mark_guilty(rq);

	} else {