linux-kernel - [tip:x86/boot] x86/reboot: Turn off KVM when halting a CPU

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Date:   Thu, 20 Apr 2017 04:16:49 -0700
From:   tip-bot for Tiantian Feng <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, fengtiantian@...wei.com,
        hpa@...or.com, tglx@...utronix.de, pbonzini@...hat.com,
        qiuxishi@...wei.com, peterz@...radead.org, mingo@...nel.org,
        torvalds@...ux-foundation.org
Subject: [tip:x86/boot] x86/reboot: Turn off KVM when halting a CPU

Commit-ID:  fba4f472b33aa81ca1836f57d005455261e9126f
Gitweb:     http://git.kernel.org/tip/fba4f472b33aa81ca1836f57d005455261e9126f
Author:     Tiantian Feng <fengtiantian@...wei.com>
AuthorDate: Wed, 19 Apr 2017 18:18:39 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 20 Apr 2017 10:06:57 +0200

x86/reboot: Turn off KVM when halting a CPU

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.

Signed-off-by: Tiantian Feng <fengtiantian@...wei.com>
Signed-off-by: Xishi Qiu <qiuxishi@...wei.com>
[ Rewritten commit message. ]
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: kvm@...r.kernel.org
Link: http://lkml.kernel.org/r/20170419161839.30550-1-pbonzini@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/smp.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c
index d3c66a1..9d7223c 100644
--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -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(unsigned int val, struct pt_regs *regs)
 	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(unsigned int val, struct pt_regs *regs)
 asmlinkage __visible void smp_reboot_interrupt(void)
 {
 	ipi_entering_ack_irq();
+	cpu_emergency_vmxoff();
 	stop_this_cpu(NULL);
 	irq_exit();
 }