Re: [RFC 0/4] pci/sriov: support VFs dynamic addition

Longpeng (Mike, Cloud Infrastructure Service Product Dept.)
2022-11-15T09:36:46Z

在 2022/11/15 16:32, Leon Romanovsky 写道:
> On Tue, Nov 15, 2022 at 12:50:34PM +1100, Oliver O'Halloran wrote:
>> On Tue, Nov 15, 2022 at 1:27 AM Leon Romanovsky <leon@kernel.org> wrote:
>>>
>>> *snip*
>>>
>>> Anyway, I'm aware of big cloud providers who are pretty happy with live
>>> migration in production.
>>
>> I could see someone sufficiently cloudbrained deciding that rebooting
>> the hypervisor is fine provided the downtime doesn't violate any
>> customer uptime SLAs. Personally I'd only be brave enough to do that
>> for a HV hosting internal services which I know are behind a load
>> balancer, but apparently there are people at Huawei far braver than I.
>
> My main point in this discussion that Huawei team doesn't actually
> provide any meaningful justification why it is great idea to add new
> sysfs file. They use HPC as an argument, but in that world, you won't
> see many VMs on one server, as it is important to provide separate MSI-X
> vectors and CPUs to each VM.
>
> They ask from us optimization (do not add device hierarchy for existing HW)
> that doesn't exist in the kernel.
>
> I would say that they are trying to meld SIOV architecture of subfunctions
> (SFs) into PCI and SR-IOV world.
>
I may not agree with you on this point. The sriov_numvfs interface mixes
the operation of enabling hardware VFs and the addition of VFs. I just
want to split these two operations and also can selectively add some VFs
earlier than others. I think there's no violation of PCI spec.

> Thanks
> .