1 files changed, 60 insertions, 2 deletions

diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index 61f718df6eec..72e0e4e712d6 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -12,6 +12,7 @@
 #include <asm/proto.h>
 #include <asm/reboot_fixups.h>
 #include <asm/reboot.h>
+#include <asm/virtext.h>
 
 #ifdef CONFIG_X86_32
 # include <linux/dmi.h>
@@ -39,6 +40,12 @@ int reboot_force;
 static int reboot_cpu = -1;
 #endif
 
+/* This is set if we need to go through the 'emergency' path.
+ * When machine_emergency_restart() is called, we may be on
+ * an inconsistent state and won't be able to do a clean cleanup
+ */
+static int reboot_emergency;
+
 /* This is set by the PCI code if either type 1 or type 2 PCI is detected */
 bool port_cf9_safe = false;
 
@@ -368,6 +375,48 @@ static inline void kb_wait(void)
         }
 }
 
+static void vmxoff_nmi(int cpu, struct die_args *args)
+{
+        cpu_emergency_vmxoff();
+}
+
+/* Use NMIs as IPIs to tell all CPUs to disable virtualization
+ */
+static void emergency_vmx_disable_all(void)
+{
+        /* Just make sure we won't change CPUs while doing this */
+        local_irq_disable();
+
+        /* We need to disable VMX on all CPUs before rebooting, otherwise
+         * we risk hanging up the machine, because the CPU ignore INIT
+         * signals when VMX is enabled.
+         *
+         * 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.
+         *
+         * 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.
+         */
+        if (cpu_has_vmx() && cpu_vmx_enabled()) {
+                /* Disable VMX on this CPU.
+                 */
+                cpu_vmxoff();
+
+                /* Halt and disable VMX on the other CPUs */
+                nmi_shootdown_cpus(vmxoff_nmi);
+
+        }
+}
+
+
 void __attribute__((weak)) mach_reboot_fixups(void)
 {
 }
@@ -376,6 +425,9 @@ static void native_machine_emergency_restart(void)
 {
         int i;
 
+        if (reboot_emergency)
+                emergency_vmx_disable_all();
+
         /* Tell the BIOS if we want cold or warm reboot */
         *((unsigned short *)__va(0x472)) = reboot_mode;
 
@@ -482,13 +534,19 @@ void native_machine_shutdown(void)
 #endif
 }
 
+static void __machine_emergency_restart(int emergency)
+{
+        reboot_emergency = emergency;
+        machine_ops.emergency_restart();
+}
+
 static void native_machine_restart(char *__unused)
 {
         printk("machine restart\n");
 
         if (!reboot_force)
                 machine_shutdown();
-        machine_emergency_restart();
+        __machine_emergency_restart(0);
 }
 
 static void native_machine_halt(void)
@@ -532,7 +590,7 @@ void machine_shutdown(void)
 
 void machine_emergency_restart(void)
 {
-        machine_ops.emergency_restart();
+        __machine_emergency_restart(1);
 }
 
 void machine_restart(char *cmd)