x86/microcode: Disable builtin microcode loading on 32-bit for now

Andy Shevchenko reported machine freezes when booting latest tip
on 32-bit setups. Problem is, the builtin microcode handling cannot
really work that early, when we haven't even enabled paging.

A proper fix would involve handling that case specially as every
other early 32-bit boot case in the microcode loader and would
require much more involved changes for which it is too late now,
more than a week before the upcoming merge window.

So, disable the builtin microcode loading on 32-bit for now.

Reported-and-tested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
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/1433436928-31903-20-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/cpu/microcode/amd_early.c

@@ -230,6 +230,7 @@ static void apply_ucode_in_initrd(void *ucode, size_t size, bool save_patch)
 
 static bool __init load_builtin_amd_microcode(struct cpio_data *cp, int family)
 {
+#ifdef CONFIG_X86_64
 	char fw_name[36] = "amd-ucode/microcode_amd.bin";
 
 	if (family >= 0x15)
@@ -237,6 +238,9 @@ static bool __init load_builtin_amd_microcode(struct cpio_data *cp, int family)
 			 "amd-ucode/microcode_amd_fam%.2xh.bin", family);
 
 	return get_builtin_firmware(cp, fw_name);
+#else
+	return false;
+#endif
 }
 
 void __init load_ucode_amd_bsp(int family)

arch/x86/kernel/cpu/microcode/intel_early.c

@@ -523,6 +523,7 @@ EXPORT_SYMBOL_GPL(save_mc_for_early);
 
 static bool __init load_builtin_intel_microcode(struct cpio_data *cp)
 {
+#ifdef CONFIG_X86_64
 	u32 eax = 0x00000001, ebx, ecx = 0, edx;
 	int family, model, stepping;
 	char name[30];
@@ -536,6 +537,9 @@ static bool __init load_builtin_intel_microcode(struct cpio_data *cp)
 	sprintf(name, "intel-ucode/%02x-%02x-%02x", family, model, stepping);
 
 	return get_builtin_firmware(cp, name);
+#else
+	return false;
+#endif
 }
 
 static __initdata char ucode_name[] = "kernel/x86/microcode/GenuineIntel.bin";