Re: [KVM PATCH v7 2/3] kvm: add support for irqfd via eventfd-notification interface

Gregory Haskins
2009-05-14T13:13:15Z

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Avi Kivity wrote:
> Gregory Haskins wrote:
>>> Please fget() the new fd and compare the filps; fds aren't meaningful
>>> in the kernel. You can also drop _irqfd::fd.
>>>
>>
>> I like this as a second option...
>>
>>
>>> It may also be useful to compare the gsi, this allows a
>>> "make-before-break" switchover:
>>>
>>
>> ...but I like this best. Good idea.
>>
>
> I thought of comparing both.

Ah, ok. I misunderstood. We can do that.
>
>>> - guest reroutes irq to a different gsi
>>> - associate irqfd with new gsi
>>> - disassociate irqfd from old gsi
>>>
>>>
>>>> +
>>>> + irqfd_release(irqfd);
>>>> + mutex_unlock(&kvm->lock);
>>>> + return 0;
>>>>
>>> Don't return, userspace may have multiple associations?
>>>
>>
>> Parse error. Can you elaborate?
>>
>>
>
> You break out of the look when you match your irqfd. But there may be
> multiple matches.
>
> Granted, it doesn't make much sense to hook the same fd to the same
> gsi multiple times (it may make sense to hook multiple fds to a single
> gsi, or maybe a single fd to multiple gsis), but it pays to have a
> consistent do-what-I-said-even-if-it-doesn't-make-sense interface.

Ack, will do.

-Greg

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