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

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Message-ID: <638b2550-7da8-1b48-4038-52f71947ff05@huawei.com>
Date:   Tue, 15 Nov 2022 17:36:38 +0800
From:   "Longpeng (Mike, Cloud Infrastructure Service Product Dept.)" 
        <longpeng2@...wei.com>
To:     Leon Romanovsky <leon@...nel.org>,
        Oliver O'Halloran <oohall@...il.com>
CC:     <bhelgaas@...gle.com>, <linux-pci@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <jianjay.zhou@...wei.com>,
        <zhuangshengen@...wei.com>, <arei.gonglei@...wei.com>,
        <yechuan@...wei.com>, <huangzhichao@...wei.com>,
        <xiehong@...wei.com>
Subject: Re: [RFC 0/4] pci/sriov: support VFs dynamic addition



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@...nel.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
> .