x86/mce: Clear Local MCE opt-in before kexec

kexec could boot a kernel that could be legacy with no knowledge
of LMCE. Hence we should make sure we clear LMCE optin before
kexec reboot.

Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@amd.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
Link: http://lkml.kernel.org/r/1439396985-12812-9-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/process.c

@@ -29,6 +29,7 @@
 #include <asm/debugreg.h>
 #include <asm/nmi.h>
 #include <asm/tlbflush.h>
+#include <asm/mce.h>
 
 /*
  * per-CPU TSS segments. Threads are completely 'soft' on Linux,
@@ -319,6 +320,7 @@ void stop_this_cpu(void *dummy)
 	 */
 	set_cpu_online(smp_processor_id(), false);
 	disable_local_APIC();
+	mcheck_cpu_clear(this_cpu_ptr(&cpu_info));
 
 	for (;;)
 		halt();