Re: [PATCH] Make virtio devices multi-function

[Anthony Liguori <anthony@codemonkey.ws>]

Marcelo Tosatti wrote:
>> Maybe require explicit device/function assignment on the command line?  
>> It will be managed anyway.
>>     
>
> ACPI does support hotplugging of individual functions inside slots,
> not sure how well does Linux (and other OSes) support that.. should be
> transparent though.
>   

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?

Regards,

Anthony Liguori



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