linux-kernel - Re: [GIT PULL] x86, microcode fixes for 3.2

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Message-ID: <20111205151016.GC7834@aftab>
Date:	Mon, 5 Dec 2011 16:10:16 +0100
From:	Borislav Petkov <bp@...64.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Jan Beulich <JBeulich@...e.com>
Subject: Re: [GIT PULL] x86, microcode fixes for 3.2

On Mon, Dec 05, 2011 at 10:26:12AM +0100, Ingo Molnar wrote:
> Mind respinning this once more against latest -git? There's a 
> new conflict due to:
> 
>   8e8da023f5af: x86: Fix boot failures on older AMD CPU's

Branch is updated, it also contains the following patch:

--
From: Borislav Petkov <borislav.petkov@....com>
Date: Mon, 5 Dec 2011 14:28:37 +0100
Subject: [PATCH] x86: Document rdmsr_safe restrictions

Recently, I got bitten by using rdmsr_safe too early in the boot
process. Document its shortcomings for future reference.

Link: http://lkml.kernel.org/r/4ED5B70F.606@lwfinger.net
Signed-off-by: Borislav Petkov <borislav.petkov@....com>
---
 arch/x86/include/asm/msr.h |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index 084ef95..95203d4 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -169,7 +169,14 @@ static inline int wrmsr_safe(unsigned msr, unsigned low, unsigned high)
 	return native_write_msr_safe(msr, low, high);
 }
 
-/* rdmsr with exception handling */
+/*
+ * rdmsr with exception handling.
+ *
+ * Please note that the exception handling works only after we've
+ * switched to the "smart" #GP handler in trap_init() which knows about
+ * exception tables - using this macro earlier than that causes machine
+ * hangs on boxes which do not implement the @msr in the first argument.
+ */
 #define rdmsr_safe(msr, p1, p2)					\
 ({								\
 	int __err;						\
-- 
1.7.8.rc0

Thanks.

-- 
Regards/Gruss,
Boris.

Advanced Micro Devices GmbH
Einsteinring 24, 85609 Dornach
GM: Alberto Bozzo
Reg: Dornach, Landkreis Muenchen
HRB Nr. 43632 WEEE Registernr: 129 19551
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