[PATCH 03 of 36] x86: add memory barriers to wrmsr

Jeremy Fitzhardinge
2008-06-25T04:39:48Z

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>
---
include/asm-x86/msr.h | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/include/asm-x86/msr.h b/include/asm-x86/msr.h
--- a/include/asm-x86/msr.h
+++ b/include/asm-x86/msr.h
@@ -66,7 +66,7 @@
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 @@
_ASM_EXTABLE(2b, 3b)
: "=a" (err)
: "c" (msr), "0" (low), "d" (high),
- "i" (-EFAULT));
+ "i" (-EFAULT)
+ : "memory");
return err;
}