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[PATCH v5] x86: call smp vmxoff in smp stop

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From: Tiantian Feng <fengtiantian@huawei.com>

A CPU in VMX root mode will ignore INIT signals and 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@huawei.com>
Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
[Rewritten commit message. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 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 d3c66a15bbde..9d7223cad389 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();
 }
-- 
2.9.3

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[PATCH v5] x86: call smp vmxoff in smp stop Paolo Bonzini <pbonzini@redhat.com> - 2017-04-19 18:20 +0200
  Re: [PATCH v5] x86: call smp vmxoff in smp stop David Hildenbrand <david@redhat.com> - 2017-04-20 12:10 +0200
    Re: [PATCH v5] x86: call smp vmxoff in smp stop Paolo Bonzini <pbonzini@redhat.com> - 2017-04-20 12:20 +0200
      Re: [PATCH v5] x86: call smp vmxoff in smp stop David Hildenbrand <david@redhat.com> - 2017-04-20 13:10 +0200
  [tip:x86/boot] x86/reboot: Turn off KVM when halting a CPU tip-bot for Tiantian Feng <tipbot@zytor.com> - 2017-04-20 13:30 +0200

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