KVM: pvmmu breakage with gcc 4.3.0

[Marcelo Tosatti <mtosatti@redhat.com>]

Some pvmmu functions store their commands on stack, and newer GCC
versions conclude that these commands are unused.

So stick an inline asm statement to convince the compiler otherwise.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>


diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 8b7a3cf..c892752 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -55,6 +55,12 @@ static void kvm_mmu_op(void *buffer, unsigned len)
 	int r;
 	unsigned long a1, a2;
 
+	/*
+   	 * GCC 4.3.0 concludes that on-stack kvm_mmu_op* is unused and
+   	 * optimizes its initialization away.
+ 	 */
+        asm ("" : : "p" (buffer));
+
 	do {
 		a1 = __pa(buffer);
 		a2 = 0;   /* on i386 __pa() always returns <4G */