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

From: tip-bot for Borislav Petkov
Date: Mon Dec 01 2014 - 04:57:48 EST

Commit-ID: 02ecc41abcea4ff9291d548f6f846b29b354ddd2
Gitweb: http://git.kernel.org/tip/02ecc41abcea4ff9291d548f6f846b29b354ddd2
Author: Borislav Petkov <bp@xxxxxxx>
AuthorDate: Sun, 30 Nov 2014 14:26:39 +0100
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
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:


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@xxxxxxx>
Link: http://lkml.kernel.org/r/1417353999-32236-1-git-send-email-bp@xxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
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)
+#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.

static struct syscore_ops mc_syscore_ops = {
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