x86: Raise vsyscall priority on hotplug notifier chain

KVM need vsyscall_init() to initialize MSR_TSC_AUX before it read the value.
Per Avi's suggestion, this patch raised vsyscall priority on hotplug notifier
chain, to 30.

CC: Ingo Molnar <mingo@elte.hu>
CC: linux-kernel@vger.kernel.org
Signed-off-by: Sheng Yang <sheng@linux.intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/x86/kernel/vsyscall_64.c

@@ -301,7 +301,8 @@ static int __init vsyscall_init(void)
 	register_sysctl_table(kernel_root_table2);
 #endif
 	on_each_cpu(cpu_vsyscall_init, NULL, 1);
-	hotcpu_notifier(cpu_vsyscall_notifier, 0);
+	/* notifier priority > KVM */
+	hotcpu_notifier(cpu_vsyscall_notifier, 30);
 	return 0;
 }