[3.11.y.z extended stable] Patch "kexec: migrate to reboot cpu" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    kexec: migrate to reboot cpu

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

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>From 4fe59c0a9f0d83cb3527fb9ec99112e50432d077 Mon Sep 17 00:00:00 2001
From: Vivek Goyal <vgoyal at redhat.com>
Date: Wed, 18 Dec 2013 17:08:31 -0800
Subject: kexec: migrate to reboot cpu

commit c97102ba96324da330078ad8619ba4dfe840dbe3 upstream.

Commit 1b3a5d02ee07 ("reboot: move arch/x86 reboot= handling to generic
kernel") moved reboot= handling to generic code.  In the process it also
removed the code in native_machine_shutdown() which are moving reboot
process to reboot_cpu/cpu0.

I guess that thought must have been that all reboot paths are calling
migrate_to_reboot_cpu(), so we don't need this special handling.  But
kexec reboot path (kernel_kexec()) is not calling
migrate_to_reboot_cpu() so above change broke kexec.  Now reboot can
happen on non-boot cpu and when INIT is sent in second kerneo to bring
up BP, it brings down the machine.

So start calling migrate_to_reboot_cpu() in kexec reboot path to avoid
this problem.

Bisected by WANG Chao.

Reported-by: Matthew Whitehead <mwhitehe at redhat.com>
Reported-by: Dave Young <dyoung at redhat.com>
Signed-off-by: Vivek Goyal <vgoyal at redhat.com>
Tested-by: Baoquan He <bhe at redhat.com>
Tested-by: WANG Chao <chaowang at redhat.com>
Acked-by: H. Peter Anvin <hpa at linux.intel.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 include/linux/reboot.h | 1 +
 kernel/kexec.c         | 1 +
 kernel/reboot.c        | 2 +-
 3 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/linux/reboot.h b/include/linux/reboot.h
index 8e00f9f..9e7db9e 100644
--- a/include/linux/reboot.h
+++ b/include/linux/reboot.h
@@ -43,6 +43,7 @@ extern int unregister_reboot_notifier(struct notifier_block *);
  * Architecture-specific implementations of sys_reboot commands.
  */

+extern void migrate_to_reboot_cpu(void);
 extern void machine_restart(char *cmd);
 extern void machine_halt(void);
 extern void machine_power_off(void);
diff --git a/kernel/kexec.c b/kernel/kexec.c
index 1f8d938..57cc094 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -1683,6 +1683,7 @@ int kernel_kexec(void)
 	{
 		kexec_in_progress = true;
 		kernel_restart_prepare(NULL);
+		migrate_to_reboot_cpu();
 		printk(KERN_EMERG "Starting new kernel\n");
 		machine_shutdown();
 	}
diff --git a/kernel/reboot.c b/kernel/reboot.c
index f813b34..662c83f 100644
--- a/kernel/reboot.c
+++ b/kernel/reboot.c
@@ -104,7 +104,7 @@ int unregister_reboot_notifier(struct notifier_block *nb)
 }
 EXPORT_SYMBOL(unregister_reboot_notifier);

-static void migrate_to_reboot_cpu(void)
+void migrate_to_reboot_cpu(void)
 {
 	/* The boot cpu is always logical cpu 0 */
 	int cpu = reboot_cpu;
--
1.8.3.2