Yes, I think it's not needed. Probably the deassign check can be turned
into an assertion?

Paolo

Il gio 30 lug 2020, 16:36 Zhenyu Ye <yezhenyu2@huawei.com> ha scritto:

> Hi all,
>
> There are checks of ioeventfd collision in both kvm_assign_ioeventfd_idx()
> and kvm_deassign_ioeventfd_idx(), however, with different logic.
>
> In kvm_assign_ioeventfd_idx(), this is done by ioeventfd_check_collision():
> ---8<---
>         if (_p->bus_idx == p->bus_idx &&
>             _p->addr == p->addr &&
>             (!_p->length || !p->length ||
>              (_p->length == p->length &&
>               (_p->wildcard || p->wildcard ||
>                _p->datamatch == p->datamatch))))
>                 // then we consider the two are the same
> ---8<---
>
> The logic in kvm_deassign_ioeventfd_idx() is as follows:
> ---8<---
>         if (p->bus_idx != bus_idx ||
>             p->eventfd != eventfd  ||
>             p->addr != args->addr  ||
>             p->length != args->len ||
>             p->wildcard != wildcard)
>                 continue;
>
>         if (!p->wildcard && p->datamatch != args->datamatch)
>                 continue;
>
>         // then we consider the two are the same
> ---8<---
>
> As we can see, there is extra check of p->eventfd in
>
> ().  Why we don't check p->eventfd
> in kvm_assign_ioeventfd_idx()? Or should we delete this in
> kvm_deassign_ioeventfd_idx()?
>
>
> Thanks,
> Zhenyu
>
>