On 07/11/2016 19:04, Alex Williamson wrote:
>> > +struct kvm *vfio_group_get_kvm(struct vfio_group *group)
>> > +{
>> > + struct kvm *kvm = NULL;
> Unnecessary initialization.
>
>> > +
>> > + mutex_lock(&group->udata.lock);
>> > +
>> > + kvm = group->udata.kvm;
>> > + if (kvm)
>> > + kvm_get_kvm(kvm);
>> > +
>> > + mutex_unlock(&group->udata.lock);
>> > +
>> > + return kvm;
>> > +}
>> > +EXPORT_SYMBOL_GPL(vfio_group_get_kvm);
>
> How are kvm references acquired through vfio_group_get_kvm() ever
> released?
They are released with kvm_put_kvm, but it's done in the vendor driver
so that VFIO core doesn't have a dependency on kvm.ko.
> Can the reference become invalid?
No, this is guaranteed by virt/kvm/vfio.c + the udata.lock mutex (which
probably should be renamed...).
> The caller may still hold
> a kvm references, but couldn't the group be detached from one kvm
> instance and re-attached to another?
Can this be handled by the vendor driver? Does it get a callback when
it's detached from a KVM instance?
Paolo
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