linux-kernel - Re: [PATCH] make KVM conform to sucky rdmsr interface

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Date:	Thu, 22 Mar 2007 18:49:30 +1100
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Avi Kivity <avi@...ranet.com>
Cc:	Andi Kleen <ak@....de>, Andrew Morton <akpm@...l.org>,
	lkml - Kernel Mailing List <linux-kernel@...r.kernel.org>,
	kvm-devel <kvm-devel@...ts.sourceforge.net>,
	Jeremy Fitzhardinge <jeremy@...p.org>
Subject: Re: [PATCH] make KVM conform to sucky rdmsr interface

On Thu, 2007-03-22 at 09:20 +0200, Avi Kivity wrote:
> My rdmsr_safe (x86_64, i386 is similar/same) is

Erk.  Andrew, please drop that patch, and take this one.

It was actually Jeremy's paravirt cleanup patch which changed the
calling convention of rdmsr_safe() to match rdmsr().

I went "oh it's that fucking rdmsr interface" and "fixed" kvm.

Sorry for the bad patch,
Rusty.
==
rdmsr_safe() takes pointers.  rdmsr() modifies its arguments.  What a
mess.

Fix rdmsr_safe() with !CONFIG_PARAVIRT.

Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>

diff -r a7f78e8eacc8 include/asm-i386/msr.h
--- a/include/asm-i386/msr.h	Thu Mar 22 12:38:35 2007 +1100
+++ b/include/asm-i386/msr.h	Thu Mar 22 18:40:35 2007 +1100
@@ -96,12 +96,12 @@ static inline void wrmsrl (unsigned long
 	(native_write_msr(msr, ((unsigned long long)val2 << 32) | val1))
 
 /* rdmsr with exception handling */
-#define rdmsr_safe(msr,val1,val2)						\
+#define rdmsr_safe(msr,p1,p2)						\
 	({								\
 		int __err;						\
-		unsigned long long __val = native_read_msr(msr, &__err);	\
-		val1 = __val;						\
-		val2 = __val >> 32;					\
+		unsigned long long __val = native_read_msr(msr, &__err);\
+		(*p1) = __val;						\
+		(*p2) = __val >> 32;					\
 		__err;							\
 	})
 


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