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From: Paolo Bonzini <pbonzini@redhat.com>
To: Zhenyu Ye <yezhenyu2@huawei.com>
Cc: gleb@redhat.com, kvm@vger.kernel.org, "S. Tsirkin,
	Michael" <mst@redhat.com>,
	linux-kernel@vger.kernel.org, kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [Question] the check of ioeventfd collision in kvm_*assign_ioeventfd_idx
Date: Fri, 31 Jul 2020 08:44:56 +0200
Message-ID: <cffcf9e1-6675-6815-ccfc-f48497ade818@redhat.com> (raw)
In-Reply-To: <4aa75d90-f2d2-888c-8970-02a41f3733e4@huawei.com>

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

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Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-30 14:19 Zhenyu Ye
2020-07-30 18:03 ` Paolo Bonzini
2020-07-31  6:39   ` Zhenyu Ye
2020-07-31  6:44     ` Paolo Bonzini [this message]
2020-07-31  8:21       ` Zhenyu Ye

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