Re: [KVM PATCH v6 2/2] KVM: add iosignalfd support

Gregory Haskins
2009-06-15T04:25:37Z

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Hi Marcelo,

Marcelo Tosatti wrote:
> On Fri, Jun 05, 2009 at 12:02:02PM -0400, Gregory Haskins wrote:
>
>> Hi Marcelo!
>>
>> Comments about the shutdown path ambiguity are in-line
>>
>> Gregory Haskins wrote:
>>
>>> iosignalfd is a mechanism to register PIO/MMIO regions to trigger an eventfd
>>> signal when written to by a guest. Host userspace can register any arbitrary
>>> IO address with a corresponding eventfd and then pass the eventfd to a
>>> + list_del(&item->list);
>>> + iosignalfd_item_free(item);
>>> + }
>>> +
>>> + list_del(&group->list);
>>> + kfree(group);
>>> +}
>>>
>>>
>> So this function is called by the path that executes as we do the last
>> kvm_put_kvm(). I do not do any careful RCU wrangling here because I
>> assume that there cannot possibly be any active MMIO/PIO operations at
>> this time, or the reference would never have dropped. Let me know if
>> anyone sees any holes in that.
>>
>> An alternative approach is to do this similar to how irqfd_release()
>> works. That is: invoke it from the vmfd release() path instead of the
>> the kvm object destructor. I currently do not think this is necessary,
>> but I will throw that out there in case someone likes it better.
>>
>
> Gregory,
>
> Can't see any problems with it.

Thanks for the review!

> You might want an upper limit
> in the number of items per group.
>

Yeah, I agree that is a good idea. Will fix in v7.

BTW: Did your series get merged while I was away?

-Greg

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