x86 / tboot / ACPI: Fail extended mode reduced hardware sleep

Register for the extended sleep callback from ACPI.

As tboot currently does not support the reduced hardware sleep
interface, fail this extended sleep call.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Ben Guthro <benjamin.guthro@citrix.com>
Cc: tboot-devel@lists.sourceforge.net
Cc: Gang Wei <gang.wei@intel.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

arch/x86/kernel/tboot.c

@@ -301,6 +301,15 @@ static int tboot_sleep(u8 sleep_state, u32 pm1a_control, u32 pm1b_control)
 	return 0;
 }
 
+static int tboot_extended_sleep(u8 sleep_state, u32 val_a, u32 val_b)
+{
+	if (!tboot_enabled())
+		return 0;
+
+	pr_warning("tboot is not able to suspend on platforms with reduced hardware sleep (ACPIv5)");
+	return -ENODEV;
+}
+
 static atomic_t ap_wfs_count;
 
 static int tboot_wait_for_aps(int num_aps)
@@ -422,6 +431,7 @@ static __init int tboot_late_init(void)
 #endif
 
 	acpi_os_set_prepare_sleep(&tboot_sleep);
+	acpi_os_set_prepare_extended_sleep(&tboot_extended_sleep);
 	return 0;
 }