This is a note to let you know that I've just added the patch titled
x86, microcode: Don't initialize microcode code on paravirt
to the 3.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-microcode-don-t-initialize-microcode-code-on-paravirt.patch
and it can be found in the queue-3.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From a18a0f6850d4b286a5ebf02cd5b22fe496b86349 Mon Sep 17 00:00:00 2001
From: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Date: Mon, 1 Dec 2014 16:27:44 -0500
Subject: x86, microcode: Don't initialize microcode code on paravirt
From: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
commit a18a0f6850d4b286a5ebf02cd5b22fe496b86349 upstream.
Paravirtual guests are not expected to load microcode into processors
and therefore it is not necessary to initialize microcode loading
logic.
In fact, under certain circumstances initializing this logic may cause
the guest to crash. Specifically, 32-bit kernels use __pa_nodebug()
macro which does not work in Xen (the code path that leads to this macro
happens during resume when we call mc_bp_resume()->load_ucode_ap()
->check_loader_disabled_ap())
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/1417469264-31470-1-git-send-email-boris.ostrovsky@xxxxxxxxxx
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/cpu/microcode/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -559,7 +559,7 @@ static int __init microcode_init(void)
struct cpuinfo_x86 *c = &cpu_data(0);
int error;
- if (dis_ucode_ldr)
+ if (paravirt_enabled() || dis_ucode_ldr)
return 0;
if (c->x86_vendor == X86_VENDOR_INTEL)
Patches currently in stable-queue which might be from boris.ostrovsky@xxxxxxxxxx are
queue-3.18/x86-microcode-don-t-initialize-microcode-code-on-paravirt.patch
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