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

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

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@xxxxxxxxxx>
---
 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;
 }
 



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