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x86: clean up comments wrt. rd{msr|tsc|pmc}

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The rdmsr instruction(et al) for i386 and x86-64 are semantically same.
The only difference is how gcc interpret constraint "A" for these targets.

Signed-off-by: Jike Song <albcamus@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Jike Song 2008-10-17 13:25:07 +08:00 committed by Ingo Molnar
parent 2011a06728
commit d4f1b10365
1 changed files with 4 additions and 4 deletions
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8
arch/x86/include/asm/msr.h
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@ -22,10 +22,10 @@ static inline unsigned long long native_read_tscp(unsigned int *aux)
} }
/* /*
* i386 calling convention returns 64-bit value in edx:eax, while * both i386 and x86_64 returns 64-bit value in edx:eax, but gcc's "A"
* x86_64 returns at rax. Also, the "A" constraint does not really * constraint has different meanings. For i386, "A" means exactly
* mean rdx:rax in x86_64, so we need specialized behaviour for each * edx:eax, while for x86_64 it doesn't mean rdx:rax or edx:eax. Instead,
* architecture * it means rax *or* rdx.
*/ */
#ifdef CONFIG_X86_64 #ifdef CONFIG_X86_64
#define DECLARE_ARGS(val, low, high) unsigned low, high #define DECLARE_ARGS(val, low, high) unsigned low, high