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authorJike Song <albcamus@gmail.com>2008-10-17 09:25:07 +0400
committerIngo Molnar <mingo@elte.hu>2008-10-28 18:47:08 +0300
commitd4f1b10365d4f03dd802433e0014cf503e6e930c (patch)
treea9ef48577063c7ab7f4e407bf08f2d742259dbd1 /arch/x86/include/asm/msr.h
parent2011a067281565494494aee194ca5081e52d6c3f (diff)
downloadlinux-d4f1b10365d4f03dd802433e0014cf503e6e930c.tar.xz
x86: clean up comments wrt. rd{msr|tsc|pmc}
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>
Diffstat (limited to 'arch/x86/include/asm/msr.h')
-rw-r--r--arch/x86/include/asm/msr.h8
1 files changed, 4 insertions, 4 deletions
diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index 46be2fa7ac26..478a9245aae1 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -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
- * x86_64 returns at rax. Also, the "A" constraint does not really
- * mean rdx:rax in x86_64, so we need specialized behaviour for each
- * architecture
+ * both i386 and x86_64 returns 64-bit value in edx:eax, but gcc's "A"
+ * constraint has different meanings. For i386, "A" means exactly
+ * edx:eax, while for x86_64 it doesn't mean rdx:rax or edx:eax. Instead,
+ * it means rax *or* rdx.
*/
#ifdef CONFIG_X86_64
#define DECLARE_ARGS(val, low, high) unsigned low, high