Re: [PATCH v6 5/5] hw/pci: ensure PCIE devices are plugged into only slot 0 of PCIE port

[Michael S. Tsirkin]

On Fri, Jun 30, 2023 at 01:11:33PM +0530, Ani Sinha wrote:
> > 
> > Thus the check for unoccupied function 0 needs to use pci_is_vf() instead 
> > of checking ARI capability, and that can happen in do_pci_register_device().
> > 
> >> Also where do you propose we move the check?
> > 
> > In pci_qdev_realize(), somewhere after pc->realize() and before option ROM 
> > loading.
> 
> Hmm, I tried this. The issue here is something like this would be now allowed 
> since the PF has ARI capability:
> 
> -device pcie-root-port,id=p -device igb,bus=p,addr=0x2.0x0
> 
> The above should not be allowed and when used, we do not see the igb ethernet 
> device from the guest OS.

I think it's allowed because it expects you to hotplug function 0 later,
no?

I am quite worried about all this work going into blocking
what we think is disallowed configurations. We should have
maybe blocked them originally, but now that we didn't
there's a non zero chance of regressions, and the benefit
is not guaranteed.

-- 
MST