On 02/10/2019 13:48, Janusz Krzysztofik wrote:
If we process DROP_RESET_ACTIVE and cancel all outstanding requests by
forcing a GPU reset on a hardware with reset capabilities disabled or
not supported, we certainly end up with a terminally wedged GPU,
impossible to recover. That's probably not what we want.
I forgot the whole background story here I'm afraid. Is the concern here
the IGT exit handler calling DROP_RESET_ACTIVE? If so with this patch it
will fail with -EBUSY, which could be fine, but what happens from the
perspective of next test which gets to run? It won't find a wedged GPU,
but will encounter a possibly nondeterministic amount of GPU work
scheduled before it, no?
Regards,
Tvrtko
Before setting the GPU wedged, verify if we have GPU reset available
and fail with -EBUSY if not.
Suggested-by: Petri Latvala <[email protected]>
Signed-off-by: Janusz Krzysztofik <[email protected]>
Cc: Michał Wajdeczko <[email protected]>
Cc: Michał Winiarski <[email protected]>
Cc: Piotr Piórkowski <[email protected]>
Cc: Tomasz Lis <[email protected]>
Cc: Petri Latvala <[email protected]>
Cc: Tvrtko Ursulin <[email protected]>
Cc: Martin Peres <[email protected]>
---
drivers/gpu/drm/i915/i915_debugfs.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/i915_debugfs.c
b/drivers/gpu/drm/i915/i915_debugfs.c
index fec9fb7cc384..0774ca6e2a05 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -3627,8 +3627,17 @@ i915_drop_caches_set(void *data, u64 val)
if (val & DROP_RESET_ACTIVE &&
wait_for(intel_engines_are_idle(&i915->gt),
- I915_IDLE_ENGINES_TIMEOUT))
+ I915_IDLE_ENGINES_TIMEOUT)) {
+ /*
+ * Only wedge if reset is supported and not disabled, otherwise
+ * we certainly end up with the GPU terminally wedged. Inform
+ * userspace about the problem instead.
+ */
+ if (!intel_has_gpu_reset(&i915->gt))
+ return -EBUSY;
+
intel_gt_set_wedged(&i915->gt);
+ }
/* No need to check and wait for gpu resets, only libdrm auto-restarts
* on ioctls on -EAGAIN. */
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