KVM: s390: SIGP START has to report BUSY while stopping a CPU

Just like the RESTART order, the START order also has to report BUSY
while a STOP request is pending, to avoid that the START might be
ignored due to a race condition between the STOP and the START order.

Signed-off-by: Thomas Huth <thuth@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
diff --git a/arch/s390/include/asm/sigp.h b/arch/s390/include/asm/sigp.h
index c002cd5..d091aa1 100644
--- a/arch/s390/include/asm/sigp.h
+++ b/arch/s390/include/asm/sigp.h
@@ -5,6 +5,7 @@
 #define SIGP_SENSE		      1
 #define SIGP_EXTERNAL_CALL	      2
 #define SIGP_EMERGENCY_SIGNAL	      3
+#define SIGP_START		      4
 #define SIGP_STOP		      5
 #define SIGP_RESTART		      6
 #define SIGP_STOP_AND_STORE_STATUS    9