drm/xe: only resume exec queues that were actually suspended

A consumer-issued suspend() can fail (e.g. the queue is killed, banned
or wedged), leaving the queue un-suspended. The consumer must then not
issue the matching resume(): resuming a queue that was never suspended
is incorrect.

Add an lr.suspended flag to struct xe_exec_queue that records whether a
consumer suspend() succeeded and a matching resume() is still owed. Set
it on a successful suspend() in the preempt-fence path, clear it on
resume(), and only resume queues that have it set.

In resume_and_reinstall_preempt_fences() also skip queues that have
since been reset/killed/banned/wedged: such a queue's suspend may not
have completed (suspend_pending can still be set, e.g. a preempt fence
signalled with -ENOENT without waiting), so resuming it would trip the
!suspend_pending assert in the backend. Leave it marked suspended and
let teardown resolve its state.

A queue is only ever suspended by a single consumer at a time
(preempt-fence mode and hw engine group fault mode are mutually
exclusive), so a single flag is sufficient.

Assisted-by: Github-Copilot:Claude-opus-4.8
Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patch.msgid.link/20260713202317.2187787-9-niranjana.vishwanathapura@intel.com

3 files changed, 36 insertions, 1 deletions

diff --git a/drivers/gpu/drm/xe/xe_exec_queue_types.h b/drivers/gpu/drm/xe/xe_exec_queue_types.h
index d27ce24daae5..dbb2ee8eb5de 100644
--- a/drivers/gpu/drm/xe/xe_exec_queue_types.h
+++ b/drivers/gpu/drm/xe/xe_exec_queue_types.h
@@ -200,6 +200,18 @@ struct xe_exec_queue {
 		u32 seqno;
 		/** @lr.link: link into VM's list of exec queues */
 		struct list_head link;
+		/**
+		 * @lr.suspended: Tracks whether the consumer-issued suspend()
+		 * succeeded and a matching resume() is still owed. suspend() can
+		 * fail (e.g. killed/banned/wedged), leaving the queue
+		 * un-suspended, so consumers must only resume() queues that were
+		 * actually suspended. Set by the suspend caller on success and
+		 * cleared by the resume caller. A queue is only ever suspended by
+		 * a single consumer at a time (preempt-fence mode and hw engine
+		 * group fault mode are mutually exclusive), so a single flag is
+		 * sufficient.
+		 */
+		bool suspended;
 	} lr;
 
 #define XE_EXEC_QUEUE_TLB_INVAL_PRIMARY_GT	0
diff --git a/drivers/gpu/drm/xe/xe_preempt_fence.c b/drivers/gpu/drm/xe/xe_preempt_fence.c
index d6427b473ddd..4aa570fe745d 100644
--- a/drivers/gpu/drm/xe/xe_preempt_fence.c
+++ b/drivers/gpu/drm/xe/xe_preempt_fence.c
@@ -74,6 +74,13 @@ static bool preempt_fence_enable_signaling(struct dma_fence *fence)
 	struct xe_exec_queue *q = pfence->q;
 
 	pfence->error = q->ops->suspend(q);
+	/*
+	 * Record a successful suspend so the rebind worker only resumes queues
+	 * that were actually suspended; a failed suspend() leaves the queue
+	 * un-suspended and must not be paired with a resume().
+	 */
+	if (!pfence->error)
+		WRITE_ONCE(q->lr.suspended, true);
 	queue_work(q->vm->xe->preempt_fence_wq, &pfence->preempt_work);
 	return true;
 }
diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
index 080c2fff0e95..23f4a9fb9a49 100644
--- a/drivers/gpu/drm/xe/xe_vm.c
+++ b/drivers/gpu/drm/xe/xe_vm.c
@@ -206,7 +206,23 @@ static void resume_and_reinstall_preempt_fences(struct xe_vm *vm,
 	xe_vm_assert_held(vm);
 
 	list_for_each_entry(q, &vm->preempt.exec_queues, lr.link) {
-		q->ops->resume(q);
+		/*
+		 * Only resume queues whose suspend() actually succeeded. A
+		 * failed suspend() (e.g. killed/banned/wedged) leaves the queue
+		 * un-suspended, so it must not be resumed.
+		 *
+		 * Also skip queues that have since been reset/killed/banned/
+		 * wedged: their suspend may not have completed (suspend_pending
+		 * can still be set, e.g. a preempt fence signalled with -ENOENT
+		 * without waiting), so resuming would trip the !suspend_pending
+		 * assert in the backend. Such queues are being torn down anyway,
+		 * so leave them marked suspended and let teardown resolve their
+		 * state.
+		 */
+		if (READ_ONCE(q->lr.suspended) && !q->ops->reset_status(q)) {
+			WRITE_ONCE(q->lr.suspended, false);
+			q->ops->resume(q);
+		}
 
 		drm_gpuvm_resv_add_fence(&vm->gpuvm, exec, q->lr.pfence,
 					 DMA_RESV_USAGE_BOOKKEEP, DMA_RESV_USAGE_BOOKKEEP);