efi/arm64: use UEFI for system reset and poweroff

If UEFI Runtime Services are available, they are preferred over direct
PSCI calls or other methods to reset the system.

For the reset case, we need to hook into machine_restart(), as the
arm_pm_restart function pointer may be overwritten by modules.

Tested-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Matt Fleming <matt.fleming@intel.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/kernel/efi.c

@@ -354,3 +354,12 @@ void efi_virtmap_unload(void)
 	efi_set_pgd(current->active_mm);
 	preempt_enable();
 }
+
+/*
+ * UpdateCapsule() depends on the system being shutdown via
+ * ResetSystem().
+ */
+bool efi_poweroff_required(void)
+{
+	return efi_enabled(EFI_RUNTIME_SERVICES);
+}

arch/arm64/kernel/process.c

@@ -21,6 +21,7 @@
 #include <stdarg.h>
 
 #include <linux/compat.h>
+#include <linux/efi.h>
 #include <linux/export.h>
 #include <linux/sched.h>
 #include <linux/kernel.h>
@@ -150,6 +151,13 @@ void machine_restart(char *cmd)
 	local_irq_disable();
 	smp_send_stop();
 
+	/*
+	 * UpdateCapsule() depends on the system being reset via
+	 * ResetSystem().
+	 */
+	if (efi_enabled(EFI_RUNTIME_SERVICES))
+		efi_reboot(reboot_mode, NULL);
+
 	/* Now call the architecture specific reboot code. */
 	if (arm_pm_restart)
 		arm_pm_restart(reboot_mode, cmd);