This is a note to let you know that I've just added the patch titled drm/i915/guc: Workaround reset G2H is received after schedule done G2H to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: drm-i915-guc-workaround-reset-g2h-is-received-after-schedule-done-g2h.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 1ca36cff0166b0483fe3b99e711e9c800ebbfaa4 Mon Sep 17 00:00:00 2001 From: Matthew Brost <matthew.brost@xxxxxxxxx> Date: Thu, 9 Sep 2021 09:47:27 -0700 Subject: drm/i915/guc: Workaround reset G2H is received after schedule done G2H From: Matthew Brost <matthew.brost@xxxxxxxxx> commit 1ca36cff0166b0483fe3b99e711e9c800ebbfaa4 upstream. If the context is reset as a result of the request cancellation the context reset G2H is received after schedule disable done G2H which is the wrong order. The schedule disable done G2H release the waiting request cancellation code which resubmits the context. This races with the context reset G2H which also wants to resubmit the context but in this case it really should be a NOP as request cancellation code owns the resubmit. Use some clever tricks of checking the context state to seal this race until the GuC firmware is fixed. v2: (Checkpatch) - Fix typos v3: (Daniele) - State that is a bug in the GuC firmware Fixes: 62eaf0ae217d ("drm/i915/guc: Support request cancellation") Signed-off-by: Matthew Brost <matthew.brost@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@xxxxxxxxx> Signed-off-by: John Harrison <John.C.Harrison@xxxxxxxxx> Link: https://patchwork.freedesktop.org/patch/msgid/20210909164744.31249-7-matthew.brost@xxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c | 41 ++++++++++++++++++---- 1 file changed, 35 insertions(+), 6 deletions(-) --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c @@ -838,17 +838,33 @@ __unwind_incomplete_requests(struct inte static void __guc_reset_context(struct intel_context *ce, bool stalled) { struct i915_request *rq; + unsigned long flags; u32 head; + bool skip = false; intel_context_get(ce); /* - * GuC will implicitly mark the context as non-schedulable - * when it sends the reset notification. Make sure our state - * reflects this change. The context will be marked enabled - * on resubmission. + * GuC will implicitly mark the context as non-schedulable when it sends + * the reset notification. Make sure our state reflects this change. The + * context will be marked enabled on resubmission. + * + * XXX: If the context is reset as a result of the request cancellation + * this G2H is received after the schedule disable complete G2H which is + * wrong as this creates a race between the request cancellation code + * re-submitting the context and this G2H handler. This is a bug in the + * GuC but can be worked around in the meantime but converting this to a + * NOP if a pending enable is in flight as this indicates that a request + * cancellation has occurred. */ - clr_context_enabled(ce); + spin_lock_irqsave(&ce->guc_state.lock, flags); + if (likely(!context_pending_enable(ce))) + clr_context_enabled(ce); + else + skip = true; + spin_unlock_irqrestore(&ce->guc_state.lock, flags); + if (unlikely(skip)) + goto out_put; rq = intel_context_find_active_request(ce); if (!rq) { @@ -867,6 +883,7 @@ static void __guc_reset_context(struct i out_replay: guc_reset_state(ce, head, stalled); __unwind_incomplete_requests(ce); +out_put: intel_context_put(ce); } @@ -1618,6 +1635,13 @@ static void guc_context_cancel_request(s guc_reset_state(ce, intel_ring_wrap(ce->ring, rq->head), true); } + + /* + * XXX: Racey if context is reset, see comment in + * __guc_reset_context(). + */ + flush_work(&ce_to_guc(ce)->ct.requests.worker); + guc_context_unblock(ce); } } @@ -2732,7 +2756,12 @@ static void guc_handle_context_reset(str { trace_intel_context_reset(ce); - if (likely(!intel_context_is_banned(ce))) { + /* + * XXX: Racey if request cancellation has occurred, see comment in + * __guc_reset_context(). + */ + if (likely(!intel_context_is_banned(ce) && + !context_blocked(ce))) { capture_error_state(guc, ce); guc_context_replay(ce); } Patches currently in stable-queue which might be from matthew.brost@xxxxxxxxx are queue-5.15/drm-i915-guc-don-t-drop-ce-guc_active.lock-when-unwinding-context.patch queue-5.15/drm-i915-guc-workaround-reset-g2h-is-received-after-schedule-done-g2h.patch queue-5.15/drm-i915-guc-fix-outstanding-g2h-accounting.patch queue-5.15/drm-i915-guc-don-t-enable-scheduling-on-a-banned-context-guc_id-invalid-not-registered.patch queue-5.15/drm-i915-guc-unwind-context-requests-in-reverse-order.patch