Re: [KVM PATCH v9 2/2] KVM: add iosignalfd support

Gregory Haskins
2009-07-07T12:57:18Z

[-- Attachment #1: Type: text/plain, Size: 1409 bytes --]

Michael S. Tsirkin wrote:
> On Tue, Jul 07, 2009 at 03:27:49PM +0300, Avi Kivity wrote:
>
>> On 07/07/2009 03:22 PM, Michael S. Tsirkin wrote:
>>
>>> On Tue, Jul 07, 2009 at 02:53:18PM +0300, Avi Kivity wrote:
>>>
>>>
>>>>>> + /* address-range must be precise for a hit */
>>>>>>
>>>>>>
>>>>>>
>>>>> So there's apparently no way to specify that
>>>>> you want 1,2, or 4 byte writes at address X?
>>>>>
>>>>>
>>>>>
>>>> Why would you want that?
>>>>
>>>>
>>> Donnu. Why would anyone want to catch 8 byte writes at all?
>>>
>>>
>> One of the natural write sizes.
>>
>>
>>> Seriously, why add artificial limitations?
>>> IMO, addr=0,len=1 and addr=0,len=2 should not conflict.
>>>
>>>
>>>
>> They should not conflict, but a two byte write need not hit a one byte
>> registration.
>>
>
> Yes. That's exactly what I'm saying. I think it should be possible to
> create 2 fds:
>
> addr = 0
> len = 1
> addr = 0
> len = 2
> and at most one will ever trigger.
>
> But current code will not let you create the second one.
>
>
Note that this was by design to keep the code simple since we don't have
a (known) use case for overlap. At the very least, you have to address
how data subsets are handled. But do we really need that functionality?

-Greg

[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 266 bytes --]