KVM: s390: sthyi: fix sthyi inline assembly

The sthyi inline assembly misses register r3 within the clobber
list. The sthyi instruction will always write a return code to
register "R2+1", which in this case would be r3. Due to that we may
have register corruption and see host crashes or data corruption
depending on how gcc decided to allocate and use registers during
compile time.

Fixes: 95ca2cb ("KVM: s390: Add sthyi emulation")
Cc: <[email protected]> # 4.8+
Reviewed-by: Janosch Frank <[email protected]>
Signed-off-by: Heiko Carstens <[email protected]>
Reviewed-by: David Hildenbrand <[email protected]>
Reviewed-by: Cornelia Huck <[email protected]>
Signed-off-by: Christian Borntraeger <[email protected]>

Author: heicarst

arch/s390/kvm/sthyi.c

@@ -394,7 +394,7 @@ static int sthyi(u64 vaddr)
 		"srl     %[cc],28\n"
 		: [cc] "=d" (cc)
 		: [code] "d" (code), [addr] "a" (addr)
-		: "memory", "cc");
+		: "3", "memory", "cc");
 	return cc;
 }