2 files changed, 28 insertions, 23 deletions

diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw_breakpoint.c
index bcaaac9e14d6..f17f581116fc 100644
--- a/arch/arm64/kernel/hw_breakpoint.c
+++ b/arch/arm64/kernel/hw_breakpoint.c
@@ -894,29 +894,10 @@ static struct notifier_block hw_breakpoint_reset_nb = {
         .notifier_call = hw_breakpoint_reset_notify,
 };
 
-#ifdef CONFIG_CPU_PM
-static int hw_breakpoint_cpu_pm_notify(struct notifier_block *self,
-                                       unsigned long action,
-                                       void *v)
-{
-        if (action == CPU_PM_EXIT) {
-                hw_breakpoint_reset(NULL);
-                return NOTIFY_OK;
-        }
-
-        return NOTIFY_DONE;
-}
-
-static struct notifier_block hw_breakpoint_cpu_pm_nb = {
-        .notifier_call = hw_breakpoint_cpu_pm_notify,
-};
-
-static void __init hw_breakpoint_pm_init(void)
-{
-        cpu_pm_register_notifier(&hw_breakpoint_cpu_pm_nb);
-}
+#ifdef CONFIG_ARM64_CPU_SUSPEND
+extern void cpu_suspend_set_dbg_restorer(void (*hw_bp_restore)(void *));
 #else
-static inline void hw_breakpoint_pm_init(void)
+static inline void cpu_suspend_set_dbg_restorer(void (*hw_bp_restore)(void *))
 {
 }
 #endif
@@ -947,7 +928,8 @@ static int __init arch_hw_breakpoint_init(void)
 
         /* Register hotplug notifier. */
         register_cpu_notifier(&hw_breakpoint_reset_nb);
-        hw_breakpoint_pm_init();
+        /* Register cpu_suspend hw breakpoint restore hook */
+        cpu_suspend_set_dbg_restorer(hw_breakpoint_reset);
 
         return 0;
 }
diff --git a/arch/arm64/kernel/suspend.c b/arch/arm64/kernel/suspend.c
index e074b1c32723..430344e2c989 100644
--- a/arch/arm64/kernel/suspend.c
+++ b/arch/arm64/kernel/suspend.c
@@ -38,6 +38,22 @@ int __cpu_suspend_finisher(unsigned long arg, struct cpu_suspend_ctx *ptr,
         return cpu_ops[cpu]->cpu_suspend(arg);
 }
 
+/*
+ * This hook is provided so that cpu_suspend code can restore HW
+ * breakpoints as early as possible in the resume path, before reenabling
+ * debug exceptions. Code cannot be run from a CPU PM notifier since by the
+ * time the notifier runs debug exceptions might have been enabled already,
+ * with HW breakpoints registers content still in an unknown state.
+ */
+void (*hw_breakpoint_restore)(void *);
+void __init cpu_suspend_set_dbg_restorer(void (*hw_bp_restore)(void *))
+{
+        /* Prevent multiple restore hook initializations */
+        if (WARN_ON(hw_breakpoint_restore))
+                return;
+        hw_breakpoint_restore = hw_bp_restore;
+}
+
 /**
  * cpu_suspend
  *
@@ -73,6 +89,13 @@ int cpu_suspend(unsigned long arg)
         if (ret == 0) {
                 cpu_switch_mm(mm->pgd, mm);
                 flush_tlb_all();
+                /*
+                 * Restore HW breakpoint registers to sane values
+                 * before debug exceptions are possibly reenabled
+                 * through local_dbg_restore.
+                 */
+                if (hw_breakpoint_restore)
+                        hw_breakpoint_restore(NULL);
         }
 
         /*