[Qemu-devel] [PATCH/RFC 2/5] KVM: s390: move finalization of SIGP STOP orders to kvm_s390_vcpu_stop

[Christian Borntraeger]

From: David Hildenbrand <address@hidden>

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 <address@hidden>
Reviewed-by: Cornelia Huck <address@hidden>
Reviewed-by: Christian Borntraeger <address@hidden>
Signed-off-by: Christian Borntraeger <address@hidden>
---
 arch/s390/kvm/intercept.c | 31 ++++++++++++-------------------
 arch/s390/kvm/kvm-s390.c  |  8 ++++++++
 2 files changed, 20 insertions(+), 19 deletions(-)

diff --git a/arch/s390/kvm/intercept.c b/arch/s390/kvm/intercept.c
index a0b586c..ac6b325 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 2f3e14f..c507789 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++) {
-- 
1.8.4.2