linux-kernel - Re: [Question] the check of ioeventfd collision in kvm_*assign_ioeventfd

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Message-ID: <18baa777-7f28-8f57-e815-11175bf4c59a@huawei.com>
Date:   Fri, 31 Jul 2020 16:21:40 +0800
From:   Zhenyu Ye <yezhenyu2@...wei.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
CC:     "S. Tsirkin, Michael" <mst@...hat.com>, <gleb@...hat.com>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <kvm@...r.kernel.org>,
        <kvmarm@...ts.cs.columbia.edu>,
        Xiexiangyou <xiexiangyou@...wei.com>
Subject: Re: [Question] the check of ioeventfd collision in
 kvm_*assign_ioeventfd_idx

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