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

[tip-bot for Borislav Petkov]

Commit-ID:  ee38a90709084b1c91279cde8f783e90f85285a1
Gitweb:     http://git.kernel.org/tip/ee38a90709084b1c91279cde8f783e90f85285a1
Author:     Borislav Petkov <bp@xxxxxxx>
AuthorDate: Thu, 4 Jun 2015 18:55:27 +0200
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Sun, 7 Jun 2015 15:38:14 +0200

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@xxxxxxxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1433436928-31903-20-git-send-email-bp@xxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/kernel/cpu/microcode/amd_early.c   | 4 ++++
 arch/x86/kernel/cpu/microcode/intel_early.c | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/arch/x86/kernel/cpu/microcode/amd_early.c b/arch/x86/kernel/cpu/microcode/amd_early.c
index 9208a36..9243cd8 100644
--- a/arch/x86/kernel/cpu/microcode/amd_early.c
+++ b/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)
diff --git a/arch/x86/kernel/cpu/microcode/intel_early.c b/arch/x86/kernel/cpu/microcode/intel_early.c
index 10dff3f..b4858d8 100644
--- a/arch/x86/kernel/cpu/microcode/intel_early.c
+++ b/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";
--
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