[tip:x86/microcode] x86/microcode/intel: Move the BUG_ON up and turn it into WARN_ON

[tip-bot for Borislav Petkov <tipbot@zytor.com>]

Commit-ID:  58b5f2cc4bdbc9b616e68639f5a84886aa5be590
Gitweb:     http://git.kernel.org/tip/58b5f2cc4bdbc9b616e68639f5a84886aa5be590
Author:     Borislav Petkov <bp@suse.de>
AuthorDate: Wed, 3 Feb 2016 12:33:38 +0100
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 9 Feb 2016 11:41:17 +0100

x86/microcode/intel: Move the BUG_ON up and turn it into WARN_ON

If we're going to BUG_ON() because we're running on the wrong CPU, we
better do it as the first thing we do when entering that function. And
also, turn it into a WARN_ON() because it is not worth to panic the
system if we apply the microcode on the wrong CPU - we're simply going
to exit early.

Tested-by: Thomas Voegtle <tv@lio96.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1454499225-21544-11-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/kernel/cpu/microcode/intel.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
index d1b2f58..c029c2b 100644
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -843,12 +843,12 @@ static int apply_microcode_intel(int cpu)
 	int cpu_num = raw_smp_processor_id();
 	struct cpuinfo_x86 *c = &cpu_data(cpu_num);
 
-	uci = ucode_cpu_info + cpu;
-	mc = uci->mc;
-
 	/* We should bind the task to the CPU */
-	BUG_ON(cpu_num != cpu);
+	if (WARN_ON(cpu_num != cpu))
+		return -1;
 
+	uci = ucode_cpu_info + cpu;
+	mc = uci->mc;
 	if (!mc)
 		return 0;