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>

2 files changed, 6 insertions, 0 deletions

diff --git a/arch/s390/include/asm/sigp.h b/arch/s390/include/asm/sigp.h
index c002cd529c71..d091aa1aaf11 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
diff --git a/arch/s390/kvm/sigp.c b/arch/s390/kvm/sigp.c
index 509547d4fca1..87c2b3a3bd3e 100644
--- a/arch/s390/kvm/sigp.c
+++ b/arch/s390/kvm/sigp.c
@@ -455,6 +455,11 @@ int kvm_s390_handle_sigp(struct kvm_vcpu *vcpu)
                 rc = __sigp_sense_running(vcpu, cpu_addr,
                                           &vcpu->run->s.regs.gprs[r1]);
                 break;
+        case SIGP_START:
+                rc = sigp_check_callable(vcpu, cpu_addr);
+                if (rc == SIGP_CC_ORDER_CODE_ACCEPTED)
+                        rc = -EOPNOTSUPP;    /* Handle START in user space */
+                break;
         case SIGP_RESTART:
                 vcpu->stat.instruction_sigp_restart++;
                 rc = sigp_check_callable(vcpu, cpu_addr);