Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

[sfrench/cifs-2.6.git] / arch / x86 / kernel / reboot.c

diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index 9991c5920aaced60bdbae9e5afbb9c7d9060b022..b29657b76e3fa1ba6db1575f145ea393af540488 100644 (file)
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -547,31 +547,21 @@ static void emergency_vmx_disable_all(void)
        local_irq_disable();
 
        /*
-        * We need to disable VMX on all CPUs before rebooting, otherwise
-        * we risk hanging up the machine, because the CPU ignores INIT
-        * signals when VMX is enabled.
+        * Disable VMX on all CPUs before rebooting, otherwise we risk hanging
+        * the machine, because the CPU blocks INIT when it's in VMX root.
         *
-        * We can't take any locks and we may be on an inconsistent
-        * state, so we use NMIs as IPIs to tell the other CPUs to disable
-        * VMX and halt.
+        * We can't take any locks and we may be on an inconsistent state, so
+        * use NMIs as IPIs to tell the other CPUs to exit VMX root and halt.
         *
-        * For safety, we will avoid running the nmi_shootdown_cpus()
-        * stuff unnecessarily, but we don't have a way to check
-        * if other CPUs have VMX enabled. So we will call it only if the
-        * CPU we are running on has VMX enabled.
-        *
-        * We will miss cases where VMX is not enabled on all CPUs. This
-        * shouldn't do much harm because KVM always enable VMX on all
-        * CPUs anyway. But we can miss it on the small window where KVM
-        * is still enabling VMX.
+        * Do the NMI shootdown even if VMX if off on _this_ CPU, as that
+        * doesn't prevent a different CPU from being in VMX root operation.
         */
-       if (cpu_has_vmx() && cpu_vmx_enabled()) {
-               /* Disable VMX on this CPU. */
-               cpu_vmxoff();
+       if (cpu_has_vmx()) {
+               /* Safely force _this_ CPU out of VMX root operation. */
+               __cpu_emergency_vmxoff();
 
-               /* Halt and disable VMX on the other CPUs */
+               /* Halt and exit VMX root operation on the other CPUs. */
                nmi_shootdown_cpus(vmxoff_nmi);
-
        }
 }