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

[Ani Sinha]

> On 30-Jun-2023, at 2:02 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
> 
> 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,

This is about the igb device being plugged into the non-zero slot of the 
pci-root-port. The guest OS ignores it.

> 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,

Sigh, no medals here for being brave :-)

> and the benefit
> is not guaranteed.
> 
> -- 
> MST
>