Improve our reboot handling for compatibility with Windows. Upstream in .38?
 
diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index c495aa8..c770e66 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -34,7 +34,7 @@ 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)
@@ -538,9 +538,23 @@ void __attribute__((weak)) mach_reboot_fixups(void)
 {
 }
 
+/*
+ * Windows does 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) Ig 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();
@@ -562,6 +576,13 @@ 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);
diff --git a/drivers/acpi/acpica/hwxface.c b/drivers/acpi/acpica/hwxface.c
index 50cc3be..c6a4e63 100644
--- a/drivers/acpi/acpica/hwxface.c
+++ b/drivers/acpi/acpica/hwxface.c
@@ -82,12 +82,11 @@ acpi_status acpi_reset(void)
 		/*
 		 * For I/O space, write directly to the OSL. This bypasses the port
 		 * validation mechanism, which may block a valid write to the reset
-		 * register.
+		 * register. Spec section 4.7.3.6 requires register width to be 8.
 		 */
 		status =
 		    acpi_os_write_port((acpi_io_address) reset_reg->address,
-				       acpi_gbl_FADT.reset_value,
-				       reset_reg->bit_width);
+				       acpi_gbl_FADT.reset_value, 8);
 	} else {
 		/* Write the reset value to the reset register */
 
diff --git a/drivers/acpi/reboot.c b/drivers/acpi/reboot.c
index 93f9114..a6c77e8b 100644
--- a/drivers/acpi/reboot.c
+++ b/drivers/acpi/reboot.c
@@ -15,9 +15,15 @@ void acpi_reboot(void)
 
 	rr = &acpi_gbl_FADT.reset_register;
 
-	/* Is the reset register supported? */
-	if (!(acpi_gbl_FADT.flags & ACPI_FADT_RESET_REGISTER) ||
-	    rr->bit_width != 8 || rr->bit_offset != 0)
+	/* ACPI reset register was only introduced with v2 of the FADT */
+
+	if (acpi_gbl_FADT.header.revision < 2)
+		return;
+
+	/* Is the reset register supported? The spec says we should be
+	 * checking the bit width and bit offset, but Windows ignores
+	 * these fields */
+	if (!(acpi_gbl_FADT.flags & ACPI_FADT_RESET_REGISTER))
 		return;
 
 	reset_value = acpi_gbl_FADT.reset_value;
@@ -45,6 +51,4 @@ void acpi_reboot(void)
 		acpi_reset();
 		break;
 	}
-	/* Wait ten seconds */
-	acpi_os_stall(10000000);
 }