drm/xe: Add timeout to preempt fences

To adhere to dma fencing rules that fences must signal within a
reasonable amount of time, add a 5 second timeout to preempt fences. If
this timeout occurs, kill the associated VM as this fatal to the VM.

v2:
 - Add comment for smp_wmb (Checkpatch)
 - Fix kernel doc typo (Inspection)
 - Add comment for killed check (Niranjana)
v3:
 - Drop smp_wmb (Matthew Auld)
 - Don't take vm->lock in preempt fence worker (Matthew Auld)
 - Drop RB given changes to patch
v4:
 - Add WRITE/READ_ONCE (Niranjana)
 - Don't export xe_vm_kill (Niranjana)

Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Tested-by: Stuart Summers <stuart.summers@intel.com>
Reviewed-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240626004137.4060806-1-matthew.brost@intel.com

drivers/gpu/drm/xe/xe_exec_queue_types.h

@@ -172,9 +172,11 @@ struct xe_exec_queue_ops {
 	int (*suspend)(struct xe_exec_queue *q);
 	/**
 	 * @suspend_wait: Wait for an exec queue to suspend executing, should be
-	 * call after suspend.
+	 * call after suspend. In dma-fencing path thus must return within a
+	 * reasonable amount of time. -ETIME return shall indicate an error
+	 * waiting for suspend resulting in associated VM getting killed.
 	 */
-	void (*suspend_wait)(struct xe_exec_queue *q);
+	int (*suspend_wait)(struct xe_exec_queue *q);
 	/**
 	 * @resume: Resume exec queue execution, exec queue must be in a suspended
 	 * state and dma fence returned from most recent suspend call must be

drivers/gpu/drm/xe/xe_execlist.c

@@ -422,10 +422,11 @@ static int execlist_exec_queue_suspend(struct xe_exec_queue *q)
 	return 0;
 }
 
-static void execlist_exec_queue_suspend_wait(struct xe_exec_queue *q)
+static int execlist_exec_queue_suspend_wait(struct xe_exec_queue *q)
 
 {
 	/* NIY */
+	return 0;
 }
 
 static void execlist_exec_queue_resume(struct xe_exec_queue *q)

drivers/gpu/drm/xe/xe_guc_submit.c

@@ -1301,6 +1301,15 @@ static void __guc_exec_queue_process_msg_set_sched_props(struct xe_sched_msg *ms
 	kfree(msg);
 }
 
+static void __suspend_fence_signal(struct xe_exec_queue *q)
+{
+	if (!q->guc->suspend_pending)
+		return;
+
+	WRITE_ONCE(q->guc->suspend_pending, false);
+	wake_up(&q->guc->suspend_wait);
+}
+
 static void suspend_fence_signal(struct xe_exec_queue *q)
 {
 	struct xe_guc *guc = exec_queue_to_guc(q);
@@ -1310,9 +1319,7 @@ static void suspend_fence_signal(struct xe_exec_queue *q)
 		  guc_read_stopped(guc));
 	xe_assert(xe, q->guc->suspend_pending);
 
-	q->guc->suspend_pending = false;
-	smp_wmb();
-	wake_up(&q->guc->suspend_wait);
+	__suspend_fence_signal(q);
 }
 
 static void __guc_exec_queue_process_msg_suspend(struct xe_sched_msg *msg)
@@ -1465,6 +1472,7 @@ static void guc_exec_queue_kill(struct xe_exec_queue *q)
 {
 	trace_xe_exec_queue_kill(q);
 	set_exec_queue_killed(q);
+	__suspend_fence_signal(q);
 	xe_guc_exec_queue_trigger_cleanup(q);
 }
 
@@ -1561,12 +1569,31 @@ static int guc_exec_queue_suspend(struct xe_exec_queue *q)
 	return 0;
 }
 
-static void guc_exec_queue_suspend_wait(struct xe_exec_queue *q)
+static int guc_exec_queue_suspend_wait(struct xe_exec_queue *q)
 {
 	struct xe_guc *guc = exec_queue_to_guc(q);
+	int ret;
+
+	/*
+	 * Likely don't need to check exec_queue_killed() as we clear
+	 * suspend_pending upon kill but to be paranoid but races in which
+	 * suspend_pending is set after kill also check kill here.
+	 */
+	ret = wait_event_timeout(q->guc->suspend_wait,
+				 !READ_ONCE(q->guc->suspend_pending) ||
+				 exec_queue_killed(q) ||
+				 guc_read_stopped(guc),
+				 HZ * 5);
 
-	wait_event(q->guc->suspend_wait, !q->guc->suspend_pending ||
-		   guc_read_stopped(guc));
+	if (!ret) {
+		xe_gt_warn(guc_to_gt(guc),
+			   "Suspend fence, guc_id=%d, failed to respond",
+			   q->guc->id);
+		/* XXX: Trigger GT reset? */
+		return -ETIME;
+	}
+
+	return 0;
 }
 
 static void guc_exec_queue_resume(struct xe_exec_queue *q)

drivers/gpu/drm/xe/xe_preempt_fence.c

@@ -17,10 +17,16 @@ static void preempt_fence_work_func(struct work_struct *w)
 		container_of(w, typeof(*pfence), preempt_work);
 	struct xe_exec_queue *q = pfence->q;
 
-	if (pfence->error)
+	if (pfence->error) {
 		dma_fence_set_error(&pfence->base, pfence->error);
-	else
-		q->ops->suspend_wait(q);
+	} else if (!q->ops->reset_status(q)) {
+		int err = q->ops->suspend_wait(q);
+
+		if (err)
+			dma_fence_set_error(&pfence->base, err);
+	} else {
+		dma_fence_set_error(&pfence->base, -ENOENT);
+	}
 
 	dma_fence_signal(&pfence->base);
 	/*

drivers/gpu/drm/xe/xe_vm.c

@@ -133,8 +133,10 @@ static int wait_for_existing_preempt_fences(struct xe_vm *vm)
 		if (q->lr.pfence) {
 			long timeout = dma_fence_wait(q->lr.pfence, false);
 
-			if (timeout < 0)
+			/* Only -ETIME on fence indicates VM needs to be killed */
+			if (timeout < 0 || q->lr.pfence->error == -ETIME)
 				return -ETIME;
+
 			dma_fence_put(q->lr.pfence);
 			q->lr.pfence = NULL;
 		}
@@ -311,6 +313,14 @@ int __xe_vm_userptr_needs_repin(struct xe_vm *vm)
 
 #define XE_VM_REBIND_RETRY_TIMEOUT_MS 1000
 
+/*
+ * xe_vm_kill() - VM Kill
+ * @vm: The VM.
+ * @unlocked: Flag indicates the VM's dma-resv is not held
+ *
+ * Kill the VM by setting banned flag indicated VM is no longer available for
+ * use. If in preempt fence mode, also kill all exec queue attached to the VM.
+ */
 static void xe_vm_kill(struct xe_vm *vm, bool unlocked)
 {
 	struct xe_exec_queue *q;