1 files changed, 23 insertions, 1 deletions

diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index 08c44b08bf5b..0c016f727695 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -36,7 +36,7 @@ EXPORT_SYMBOL(pm_power_off);
 
 static const struct desc_ptr no_idt = {};
 static int reboot_mode;
-enum reboot_type reboot_type = BOOT_KBD;
+enum reboot_type reboot_type = BOOT_ACPI;
 int reboot_force;
 
 #if defined(CONFIG_X86_32) && defined(CONFIG_SMP)
@@ -478,9 +478,24 @@ void __attribute__((weak)) mach_reboot_fixups(void)
 {
 }
 
+/*
+ * Windows compatible x86 hardware expects the following on reboot:
+ *
+ * 1) If the FADT has the ACPI reboot register flag set, try it
+ * 2) If still alive, write to the keyboard controller
+ * 3) If still alive, write to the ACPI reboot register again
+ * 4) If still alive, write to the keyboard controller again
+ *
+ * If the machine is still alive at this stage, it gives up. We default to
+ * following the same pattern, except that if we're still alive after (4) we'll
+ * try to force a triple fault and then cycle between hitting the keyboard
+ * controller and doing that
+ */
 static void native_machine_emergency_restart(void)
 {
         int i;
+        int attempt = 0;
+        int orig_reboot_type = reboot_type;
 
         if (reboot_emergency)
                 emergency_vmx_disable_all();
@@ -502,6 +517,13 @@ static void native_machine_emergency_restart(void)
                                 outb(0xfe, 0x64); /* pulse reset low */
                                 udelay(50);
                         }
+                        if (attempt == 0 && orig_reboot_type == BOOT_ACPI) {
+                                attempt = 1;
+                                reboot_type = BOOT_ACPI;
+                        } else {
+                                reboot_type = BOOT_TRIPLE;
+                        }
+                        break;
 
                 case BOOT_TRIPLE:
                         load_idt(&no_idt);