drm/xe: Block exec and rebind worker while evicting for suspend / hibernate

When the xe pm_notifier evicts for suspend / hibernate, there might be
racing tasks trying to re-validate again. This can lead to suspend taking
excessive time or get stuck in a live-lock. This behaviour becomes
much worse with the fix that actually makes re-validation bring back
bos to VRAM rather than letting them remain in TT.

Prevent that by having exec and the rebind worker waiting for a completion
that is set to block by the pm_notifier before suspend and is signaled
by the pm_notifier after resume / wakeup.

It's probably still possible to craft malicious applications that block
suspending. More work is pending to fix that.

v3:
- Avoid wait_for_completion() in the kernel worker since it could
  potentially cause work item flushes from freezable processes to
  wait forever. Instead terminate the rebind workers if needed and
  re-launch at resume. (Matt Auld)
v4:
- Fix some bad naming and leftover debug printouts.
- Fix kerneldoc.
- Use drmm_mutex_init() for the xe->rebind_resume_lock (Matt Auld).
- Rework the interface of xe_vm_rebind_resume_worker (Matt Auld).

Link: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/4288
Fixes: c6a4d46ec1d7 ("drm/xe: evict user memory in PM notifier")
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: <stable@vger.kernel.org> # v6.16+
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://lore.kernel.org/r/20250904160715.2613-4-thomas.hellstrom@linux.intel.com

1 files changed, 25 insertions, 0 deletions

diff --git a/drivers/gpu/drm/xe/xe_pm.c b/drivers/gpu/drm/xe/xe_pm.c
index ecfa7d77a2a3..6eea4190bbd2 100644
--- a/drivers/gpu/drm/xe/xe_pm.c
+++ b/drivers/gpu/drm/xe/xe_pm.c
@@ -25,6 +25,7 @@
 #include "xe_pxp.h"
 #include "xe_sriov_vf_ccs.h"
 #include "xe_trace.h"
+#include "xe_vm.h"
 #include "xe_wa.h"
 
 /**
@@ -301,6 +302,19 @@ static u32 vram_threshold_value(struct xe_device *xe)
 	return DEFAULT_VRAM_THRESHOLD;
 }
 
+static void xe_pm_wake_rebind_workers(struct xe_device *xe)
+{
+	struct xe_vm *vm, *next;
+
+	mutex_lock(&xe->rebind_resume_lock);
+	list_for_each_entry_safe(vm, next, &xe->rebind_resume_list,
+				 preempt.pm_activate_link) {
+		list_del_init(&vm->preempt.pm_activate_link);
+		xe_vm_resume_rebind_worker(vm);
+	}
+	mutex_unlock(&xe->rebind_resume_lock);
+}
+
 static int xe_pm_notifier_callback(struct notifier_block *nb,
 				   unsigned long action, void *data)
 {
@@ -310,6 +324,7 @@ static int xe_pm_notifier_callback(struct notifier_block *nb,
 	switch (action) {
 	case PM_HIBERNATION_PREPARE:
 	case PM_SUSPEND_PREPARE:
+		reinit_completion(&xe->pm_block);
 		xe_pm_runtime_get(xe);
 		err = xe_bo_evict_all_user(xe);
 		if (err)
@@ -326,6 +341,8 @@ static int xe_pm_notifier_callback(struct notifier_block *nb,
 		break;
 	case PM_POST_HIBERNATION:
 	case PM_POST_SUSPEND:
+		complete_all(&xe->pm_block);
+		xe_pm_wake_rebind_workers(xe);
 		xe_bo_notifier_unprepare_all_pinned(xe);
 		xe_pm_runtime_put(xe);
 		break;
@@ -352,6 +369,14 @@ int xe_pm_init(struct xe_device *xe)
 	if (err)
 		return err;
 
+	err = drmm_mutex_init(&xe->drm, &xe->rebind_resume_lock);
+	if (err)
+		goto err_unregister;
+
+	init_completion(&xe->pm_block);
+	complete_all(&xe->pm_block);
+	INIT_LIST_HEAD(&xe->rebind_resume_list);
+
 	/* For now suspend/resume is only allowed with GuC */
 	if (!xe_device_uc_enabled(xe))
 		return 0;