Re: [kvm-devel] [PATCH] Make virtio devices multi-function

[Avi K. <av...@qu...>]

Anthony Liguori wrote:
>
> I think we need to decide what we want to target in terms of upper 
> limits.
>
> With a bridge or two, we can probably easily do 128.
>
> If we really want to push things, I think we should do a PCI based 
> virtio controller.  I doubt a large number of PCI devices is ever 
> going to perform very well b/c of interrupt sharing and some of the 
> assumptions in virtio_pci.
>
> If we implement a controller, we can use a single interrupt, but 
> multiplex multiple notifications on that single interrupt.  We can 
> also be more aggressive about using shared memory instead of PCI 
> config space which would reduce the overall number of exits.
>
> We could easily support a very large number of devices this way.  But 
> again, what do we want to target for now? 

I think that for networking we should keep things as is.  I don't see 
anybody using 100 virtual NICs.

For mass storage, we should follow the SCSI model with a single device 
serving multiple disks, similar to what you suggest.  Not sure if the 
device should have a single queue or one queue per disk.

-- 
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