x86, microcode: Limit the microcode reloading to 64-bit for now

First, there was this: https://bugzilla.kernel.org/show_bug.cgi?id=88001

The problem there was that microcode patches are not being reapplied
after suspend-to-ram. It was important to reapply them, though, because
of for example Haswell's TSX erratum which disabled TSX instructions
with a microcode patch.

A simple fix was fb86b97300d9 ("x86, microcode: Update BSPs microcode
on resume") but, as it is often the case, simple fixes are too
simple. This one causes 32-bit resume to fail:

https://bugzilla.kernel.org/show_bug.cgi?id=88391

Properly fixing this would require more involved changes for which it
is too late now, right before the merge window. Thus, limit this to
64-bit only temporarily.

Signed-off-by: Borislav Petkov <bp@suse.de>
Link: http://lkml.kernel.org/r/1417353999-32236-1-git-send-email-bp@alien8.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index 2ce9051174e6..08fe6e8a726e 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -465,6 +465,7 @@ static void mc_bp_resume(void)
 
         if (uci->valid && uci->mc)
                 microcode_ops->apply_microcode(cpu);
+#ifdef CONFIG_X86_64
         else if (!uci->mc)
                 /*
                  * We might resume and not have applied late microcode but still
@@ -473,6 +474,7 @@ static void mc_bp_resume(void)
                  * applying patches early on the APs.
                  */
                 load_ucode_ap();
+#endif
 }
 
 static struct syscore_ops mc_syscore_ops = {