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x86: add memory barriers to wrmsr

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wrmsr is a special instruction which can have arbitrary system-wide
effects.  We don't want the compiler to reorder it with respect to
memory operations, so make it a memory barrier.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: xen-devel <xen-devel@lists.xensource.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Jeremy Fitzhardinge 2008-06-25 00:18:59 -04:00 committed by Ingo Molnar
parent d338c73c39
commit af2b1c609f
1 changed files with 3 additions and 2 deletions
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5
include/asm-x86/msr.h
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@ -66,7 +66,7 @@ static inline unsigned long long native_read_msr_safe(unsigned int msr,
static inline void native_write_msr(unsigned int msr,
unsigned low, unsigned high)
{
asm volatile("wrmsr" : : "c" (msr), "a"(low), "d" (high));
asm volatile("wrmsr" : : "c" (msr), "a"(low), "d" (high) : "memory");
}
static inline int native_write_msr_safe(unsigned int msr,
@ -81,7 +81,8 @@ static inline int native_write_msr_safe(unsigned int msr,
_ASM_EXTABLE(2b, 3b)
: "=a" (err)
: "c" (msr), "0" (low), "d" (high),
"i" (-EFAULT));
"i" (-EFAULT)
: "memory");
return err;
}