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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@huawei.com>
AuthorDate: Wed, 19 Apr 2017 18:18:39 +0200
Committer: Ingo Molnar <mingo@kernel.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@huawei.com>
Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
[ Rewritten commit message. ]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm@vger.kernel.org
Link: http://lkml.kernel.org/r/20170419161839.30550-1-pbonzini@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.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();
}
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