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
On 2020/7/31 2:03, Paolo Bonzini wrote:
> Yes, I think it's not needed. Probably the deassign check can be turned into an assertion?
>
> Paolo
>
I think we can do this in the same function, and turnt he check of
p->eventfd into assertion in kvm_deassign_ioeventfd_idx(). Just like:
---8<---
static inline struct _ioeventfd *
get_ioeventfd(struct kvm *kvm, enum kvm_bus bus_idx,
struct kvm_ioeventfd *args)
{
static struct _ioeventfd *_p;
bool wildcard = !(args->flags & KVM_IOEVENTFD_FLAG_DATAMATCH);
list_for_each_entry(_p, &kvm->ioeventfds, list)
if (_p->bus_idx == bus_idx &&
_p->addr == args->addr &&
(!_p->length || !args->len ||
(_p->length == args->len &&
(_p->wildcard || wildcard ||
_p->datamatch == args->datamatch))))
return _p;
return NULL;
}
kvm_deassign_ioeventfd_idx() {
...
p = get_ioeventfd(kvm, bus_idx, args);
if (p) {
assert(p->eventfd == eventfd);
...
}
---8<----
This may be easier to understand (keep the same logic in assign/deassign).
I will send a formal patch soon.
Thanks,
Zhenyu
> Il gio 30 lug 2020, 16:36 Zhenyu Ye <[email protected] <mailto:[email protected]>> 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
>
On 31/07/20 08:39, Zhenyu Ye wrote:
> On 2020/7/31 2:03, Paolo Bonzini wrote:
>> Yes, I think it's not needed. Probably the deassign check can be turned into an assertion?
>>
>> Paolo
>>
>
> I think we can do this in the same function, and turnt he check of
> p->eventfd into assertion in kvm_deassign_ioeventfd_idx(). Just like:
>
> ---8<---
> static inline struct _ioeventfd *
> get_ioeventfd(struct kvm *kvm, enum kvm_bus bus_idx,
> struct kvm_ioeventfd *args)
> {
> static struct _ioeventfd *_p;
> bool wildcard = !(args->flags & KVM_IOEVENTFD_FLAG_DATAMATCH);
>
> list_for_each_entry(_p, &kvm->ioeventfds, list)
> if (_p->bus_idx == bus_idx &&
> _p->addr == args->addr &&
> (!_p->length || !args->len ||
> (_p->length == args->len &&
> (_p->wildcard || wildcard ||
> _p->datamatch == args->datamatch))))
> return _p;
>
> return NULL;
> }
>
> kvm_deassign_ioeventfd_idx() {
> ...
> p = get_ioeventfd(kvm, bus_idx, args);
> if (p) {
> assert(p->eventfd == eventfd);
> ...
> }
>
> ---8<----
>
> This may be easier to understand (keep the same logic in assign/deassign).
I think you should also warn if:
1) p->length != args->len
2) p->wildcard != args->wildcard if p->length
3) p->datamatch != args->datamatch if p->length && !p->wildcard
but yeah it sounds like a plan.
Paolo
On 2020/7/31 14:44, Paolo Bonzini wrote:
> On 31/07/20 08:39, Zhenyu Ye wrote:
>> On 2020/7/31 2:03, Paolo Bonzini wrote:
>>> Yes, I think it's not needed. Probably the deassign check can be turned into an assertion?
>>>
>>> Paolo
>>>
>>
>> I think we can do this in the same function, and turnt he check of
>> p->eventfd into assertion in kvm_deassign_ioeventfd_idx(). Just like:
>>
>> ---8<---
>> static inline struct _ioeventfd *
>> get_ioeventfd(struct kvm *kvm, enum kvm_bus bus_idx,
>> struct kvm_ioeventfd *args)
>> {
>> static struct _ioeventfd *_p;
>> bool wildcard = !(args->flags & KVM_IOEVENTFD_FLAG_DATAMATCH);
>>
>> list_for_each_entry(_p, &kvm->ioeventfds, list)
>> if (_p->bus_idx == bus_idx &&
>> _p->addr == args->addr &&
>> (!_p->length || !args->len ||
>> (_p->length == args->len &&
>> (_p->wildcard || wildcard ||
>> _p->datamatch == args->datamatch))))
>> return _p;
>>
>> return NULL;
>> }
>>
>> kvm_deassign_ioeventfd_idx() {
>> ...
>> p = get_ioeventfd(kvm, bus_idx, args);
>> if (p) {
>> assert(p->eventfd == eventfd);
>> ...
>> }
>>
>> ---8<----
>>
>> This may be easier to understand (keep the same logic in assign/deassign).
>
> I think you should also warn if:
>
> 1) p->length != args->len
>
> 2) p->wildcard != args->wildcard if p->length
>
> 3) p->datamatch != args->datamatch if p->length && !p->wildcard
>
> but yeah it sounds like a plan.
>
I will try to do this. :)
Zhenyu