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%3Ba=su...

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 stable@vger.kernel.org know about it.

From foo@baz Thu Mar 22 14:40:23 CET 2018

From: Tiantian Feng fengtiantian@huawei.com Date: Wed, 19 Apr 2017 18:18:39 +0200 Subject: x86/reboot: Turn off KVM when halting a CPU

From: Tiantian Feng fengtiantian@huawei.com

[ 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.

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 Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kernel/smp.c | 3 +++ 1 file changed, 3 insertions(+)

--- 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(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 fengtiantian@huawei.com are

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