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    Subject[PATCH 4.9 035/177] x86/reboot: Turn off KVM when halting a CPU
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    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();
    }

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