Hi,

this change is also useful for SEV-ES guests.

The hypervisor reads and writes the GHCB while handling a VMGEXIT.
Without a memory clobber the compiler may cache GHCB contents across
the instruction.  "asm volatile" alone does not prevent that.

No change in generated code.

ok?

Take care,
HJ.
---
 sys/arch/amd64/include/cpufunc.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sys/arch/amd64/include/cpufunc.h b/sys/arch/amd64/include/cpufunc.h
index 96af50a82a5..6e8b63abf4f 100644
--- a/sys/arch/amd64/include/cpufunc.h
+++ b/sys/arch/amd64/include/cpufunc.h
@@ -436,7 +436,7 @@ static __inline void
 vmgexit(void)
 {
 	/* rep; vmmcall encodes the vmgexit instruction */
-	__asm volatile("rep; vmmcall");
+	__asm volatile("rep; vmmcall" : : : "memory");
 }
 
 void amd64_errata(struct cpu_info *);
-- 
2.47.3