linux-kernel - [PATCH] x86/reboot: Enable restart

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Date:   Fri, 17 Jan 2020 15:45:35 +0200
From:   Benjamin Bouvier <benjamin.bouvier@...ia.com>
To:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de
Cc:     hpa@...or.com, x86@...nel.org, linux-kernel@...r.kernel.org,
        Benjamin Bouvier <benjamin.bouvier@...ia.com>,
        Patrick Lelu <patrick.lelu@...ia.com>
Subject: [PATCH] x86/reboot: Enable restart_handler mechanism

Drivers may want to register restart_handlers for case where an external
reset is needed to reset a complete system and not only the processor.
This case is currently missing in x86 architecture.
So include call to do_kernel_restart() to use handlers registered
through register_restart_handler() API when the processor restarts.

do_kernel_restart() cannot be called in machine_restart() as required by
documentation as final step, because it will never be reached (restart
having already been carried out). So call is done inside
native_machine_restart(), and only here to not let drivers managed reset
in hypervisor case where function native_machine_restart() is overridden.

Co-developed-by: Patrick Lelu <patrick.lelu@...ia.com>
Signed-off-by: Patrick Lelu <patrick.lelu@...ia.com>
Signed-off-by: Benjamin Bouvier <benjamin.bouvier@...ia.com>
---
 arch/x86/kernel/reboot.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index 0cc7c0b106bb..53c3d5a3f89d 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -718,12 +718,13 @@ 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_restart(cmd);
 	__machine_emergency_restart(0);
 }

-- 
2.21.0