Patch "x86/reboot: Turn off KVM when halting a CPU" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

x86/reboot: Turn off KVM when halting a CPU

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
x86-reboot-turn-off-kvm-when-halting-a-cpu.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Tiantian Feng <[email protected]>
Date: Wed, 19 Apr 2017 18:18:39 +0200
Subject: x86/reboot: Turn off KVM when halting a CPU

From: Tiantian Feng <[email protected]>

[ Upstream commit fba4f472b33aa81ca1836f57d005455261e9126f ]

A CPU in VMX root mode will ignore INIT signals and will fail to bring up the APs after reboot. Therefore, on a panic we disable VMX on all CPUs before rebooting or triggering kdump.

Do this when halting the machine as well, in case a firmware-level reboot does not perform a cold reset for all processors. Without doing this, rebooting the host may hang.

---
 arch/x86/kernel/smp.c |    3 +++
 1 file changed, 3 insertions(+)

@@ -33,6 +33,7 @@
 #include <asm/mce.h>
 #include <asm/trace/irq_vectors.h>
 #include <asm/kexec.h>
+#include <asm/virtext.h>
 
 /*
  *	Some notes on x86 processor bugs affecting SMP operation:

@@ -162,6 +163,7 @@ static int smp_stop_nmi_callback(unsigne
 	if (raw_smp_processor_id() == atomic_read(&stopping_cpu))
 		return NMI_HANDLED;
 
+	cpu_emergency_vmxoff();
 	stop_this_cpu(NULL);
 
 	return NMI_HANDLED;

@@ -174,6 +176,7 @@ static int smp_stop_nmi_callback(unsigne
 asmlinkage __visible void smp_reboot_interrupt(void)
 {
 	ipi_entering_ack_irq();
+	cpu_emergency_vmxoff();
 	stop_this_cpu(NULL);
 	irq_exit();
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/x86-reboot-turn-off-kvm-when-halting-a-cpu.patch