KVM: s390: move finalization of SIGP STOP orders to kvm_s390_vcpu_stop

Let's move the finalization of SIGP STOP and SIGP STOP AND STORE STATUS orders to
the point where the VCPU is actually stopped.

This change is needed to prepare for a user space driven VCPU state change. The
action_bits may only be cleared when setting the cpu state to STOPPED while
holding the local irq lock.

Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

2 files changed, 20 insertions, 19 deletions

diff --git a/arch/s390/kvm/intercept.c b/arch/s390/kvm/intercept.c
index a0b586c1913c..ac6b32585a36 100644
--- a/arch/s390/kvm/intercept.c
+++ b/arch/s390/kvm/intercept.c
@@ -56,32 +56,25 @@ static int handle_noop(struct kvm_vcpu *vcpu)
 static int handle_stop(struct kvm_vcpu *vcpu)
 {
         int rc = 0;
+        unsigned int action_bits;
 
         vcpu->stat.exit_stop_request++;
-        spin_lock_bh(&vcpu->arch.local_int.lock);
-
         trace_kvm_s390_stop_request(vcpu->arch.local_int.action_bits);
 
-        if (vcpu->arch.local_int.action_bits & ACTION_STOP_ON_STOP) {
-                kvm_s390_vcpu_stop(vcpu);
-                vcpu->arch.local_int.action_bits &= ~ACTION_STOP_ON_STOP;
-                VCPU_EVENT(vcpu, 3, "%s", "cpu stopped");
-                rc = -EOPNOTSUPP;
-        }
+        action_bits = vcpu->arch.local_int.action_bits;
 
-        if (vcpu->arch.local_int.action_bits & ACTION_STORE_ON_STOP) {
-                vcpu->arch.local_int.action_bits &= ~ACTION_STORE_ON_STOP;
-                /* store status must be called unlocked. Since local_int.lock
-                 * only protects local_int.* and not guest memory we can give
-                 * up the lock here */
-                spin_unlock_bh(&vcpu->arch.local_int.lock);
+        if (!(action_bits & ACTION_STOP_ON_STOP))
+                return 0;
+
+        if (action_bits & ACTION_STORE_ON_STOP) {
                 rc = kvm_s390_vcpu_store_status(vcpu,
                                                 KVM_S390_STORE_STATUS_NOADDR);
-                if (rc >= 0)
-                        rc = -EOPNOTSUPP;
-        } else
-                spin_unlock_bh(&vcpu->arch.local_int.lock);
-        return rc;
+                if (rc)
+                        return rc;
+        }
+
+        kvm_s390_vcpu_stop(vcpu);
+        return -EOPNOTSUPP;
 }
 
 static int handle_validity(struct kvm_vcpu *vcpu)
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 2f3e14fe91a4..c5077899de5b 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -1494,7 +1494,15 @@ void kvm_s390_vcpu_stop(struct kvm_vcpu *vcpu)
         spin_lock_bh(&vcpu->kvm->arch.start_stop_lock);
         online_vcpus = atomic_read(&vcpu->kvm->online_vcpus);
 
+        /* Need to lock access to action_bits to avoid a SIGP race condition */
+        spin_lock_bh(&vcpu->arch.local_int.lock);
         atomic_set_mask(CPUSTAT_STOPPED, &vcpu->arch.sie_block->cpuflags);
+
+        /* SIGP STOP and SIGP STOP AND STORE STATUS has been fully processed */
+        vcpu->arch.local_int.action_bits &=
+                                 ~(ACTION_STOP_ON_STOP | ACTION_STORE_ON_STOP);
+        spin_unlock_bh(&vcpu->arch.local_int.lock);
+
         __disable_ibs_on_vcpu(vcpu);
 
         for (i = 0; i < online_vcpus; i++) {