[RFC PATCH 4/4] x86: Invoke pre_restart notifiers

[Mathieu Desnoyers <mathieu.desnoyers@efficios.com>]

Invoke the pre_restart notifiers after shutdown, before machine restart.
This allows preserving pmem memory across warm reboots.

Invoke the pre_restart notifiers on emergency_machine_restart to cover
the panic() scenario.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: nvdimm@lists.linux.dev
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
---
 arch/x86/kernel/reboot.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index f3130f762784..222619fa63c6 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -631,8 +631,10 @@ static void native_machine_emergency_restart(void)
 	int orig_reboot_type = reboot_type;
 	unsigned short mode;
 
-	if (reboot_emergency)
+	if (reboot_emergency) {
+		do_kernel_pre_restart(NULL);
 		emergency_reboot_disable_virtualization();
+	}
 
 	tboot_shutdown(TB_SHUTDOWN_REBOOT);
 
@@ -760,12 +762,13 @@ static void __machine_emergency_restart(int emergency)
 	machine_ops.emergency_restart();
 }
 
-static void native_machine_restart(char *__unused)
+static void native_machine_restart(char *cmd)
 {
 	pr_notice("machine restart\n");
 
 	if (!reboot_force)
 		machine_shutdown();
+	do_kernel_pre_restart(cmd);
 	__machine_emergency_restart(0);
 }
 
-- 
2.39.2