[PATCH v1 3/8] KVM: s390: Fix unlikely race with KVM_CAP_S390_USER_OPEREXEC

[Claudio Imbrenda <imbrenda@linux.ibm.com>]

Due to a missing barrier, it was theoretically possible that a vCPU
being created concurrently with enabling KVM_CAP_S390_USER_OPEREXEC
would end up with the capability not enabled.

Fix by using WRITE_ONCE(), which is enough on s390.

Fixes: 8e8678e740ec ("KVM: s390: Add capability that forwards operation exceptions")
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
---
 arch/s390/kvm/kvm-s390.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 4a6d903e3523..784f7d9c79c7 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -955,7 +955,7 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap)
 		break;
 	case KVM_CAP_S390_USER_OPEREXEC:
 		VM_EVENT(kvm, 3, "%s", "ENABLE: CAP_S390_USER_OPEREXEC");
-		kvm->arch.user_operexec = 1;
+		WRITE_ONCE(kvm->arch.user_operexec, 1);
 		icpt_operexc_on_all_vcpus(kvm);
 		r = 0;
 		break;
-- 
2.55.0