linux-kernel - [tip:x86/urgent] x86, microcode: Limit the microcode reloading to 64-bit for now

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Date:	Mon, 1 Dec 2014 01:57:30 -0800
From:	tip-bot for Borislav Petkov <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, mingo@...nel.org, tglx@...utronix.de,
	hpa@...or.com, bp@...e.de
Subject: [tip:x86/urgent] x86, microcode:
  Limit the microcode reloading to 64-bit for now

Commit-ID:  02ecc41abcea4ff9291d548f6f846b29b354ddd2
Gitweb:     http://git.kernel.org/tip/02ecc41abcea4ff9291d548f6f846b29b354ddd2
Author:     Borislav Petkov <bp@...e.de>
AuthorDate: Sun, 30 Nov 2014 14:26:39 +0100
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Mon, 1 Dec 2014 10:55:08 +0100

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@...e.de>
Link: http://lkml.kernel.org/r/1417353999-32236-1-git-send-email-bp@alien8.de
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 arch/x86/kernel/cpu/microcode/core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index 2ce9051..08fe6e8 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 = {
--
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