Re: [PATCH v3 0/2] kvm: level irqfd and new eoifd

[Avi Kivity <avi@redhat.com>]

On 07/11/2012 01:18 PM, Jan Kiszka wrote:
> On 2012-07-11 11:53, Avi Kivity wrote:
>> On 07/03/2012 10:21 PM, Alex Williamson wrote:
>>> Here's the latest iteration of adding an interface to assert and
>>> de-assert level interrupts from external drivers like vfio.  These
>>> apply on top of the previous argument cleanup, documentation, and
>>> sanitization patches for irqfd.  It would be great to get this queued
>>> in next for linux 3.6.
>>>
>>> I believe I've addressed all the previous comments, including fixing
>>> the locking problems in eoifd.  I've run this with lockdep adding
>>> and removing level irqfd/eoifd pairs without any problems.  Please
>>> let me know if there are any further comments.  Thanks,
>> 
>> Is there any performance justification for level irqfd?  Don't all
>> new/high bandwidth devices support msi, and this is just a legacy path?
> 
> I think we've been there before, but the situation hasn't improved much:
> 
> Apparently, some GPUs still prefer INTx over MSI. Some wireless chipsets
> too. 

I'd appreciate a couple of examples for formality's sake.

> And then there is not easily replaceable legacy hardware like old
> telephony adapters or industrial I/O cards etc. that want this.

I imagine legacy hardware will live with the speed of routing through
qemu, when running on modern platforms.

-- 
error compiling committee.c: too many arguments to function