KVM: document memory barriers for kvm->vcpus/kvm->online_vcpus
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index bd1097a..81089cf 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -427,6 +427,10 @@
static inline struct kvm_vcpu *kvm_get_vcpu(struct kvm *kvm, int i)
{
+ /* Pairs with smp_wmb() in kvm_vm_ioctl_create_vcpu, in case
+ * the caller has read kvm->online_vcpus before (as is the case
+ * for kvm_for_each_vcpu, for example).
+ */
smp_rmb();
return kvm->vcpus[i];
}
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 8dc4828..d8db2f8f 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2206,6 +2206,11 @@
}
kvm->vcpus[atomic_read(&kvm->online_vcpus)] = vcpu;
+
+ /*
+ * Pairs with smp_rmb() in kvm_get_vcpu. Write kvm->vcpus
+ * before kvm->online_vcpu's incremented value.
+ */
smp_wmb();
atomic_inc(&kvm->online_vcpus);
