Re: [virtio-comment] About the plan of Admin Queue

[Xuan Zhuo <xuanzhuo@linux.alibaba.com>]

On Mon, 3 Jul 2023 12:29:32 +0800, "Zhu, Lingshan" <lingshan.zhu@intel.com> wrote:
>
>
> On 6/30/2023 7:35 PM, Parav Pandit wrote:
> >> From: virtio-comment@lists.oasis-open.org <virtio-comment@lists.oasis-
> >> open.org> On Behalf Of Zhu, Lingshan
> >> Sent: Friday, June 30, 2023 6:33 AM
> >>
> >
> >>>>> Can we let the DPU notify the driver to create a new devicer from the
> >> backend?
> > Yes, why not.
> >
> >>>>> The key point is who want to create a new device.
> >>>> DPU can come with a certain number of pre-created ADIs, just make
> >>>> sure the orchestration SW is aware of their device IDs.
> >>>>
> > Cloud often need these devices to be created dynamically, many a time after the host OS is booted.
> > To be more generic, those devices to be created and connected to the host regardless of the life cycle of the host.
> > Xuan partly explained it.
> >
> >>>> If you want the DPU randomly create ADIs and notify the driver, I
> >>>> think we need interrupt, e.g., re-use config interrupt. But why DPU
> >>>> wants to create and hot plug in a device to a guest?
> >>>> Shall the host handle that or DPU pre-create then expose to baremteal
> >>>> machines?
> >>> In your scenario, the supervisor is on the os, which controls the DPU
> >>> to create new devices.
> >>>
> >>> In the cloud scenario, the vendor manager is in the DPU, and the
> >>> entire host is for users. Of course, there are situations where the
> >>> vendor manager are in the HOST. But for bare metal machines, the host
> >>> belongs to the customer, the vendor manager is only in the DPU.
> >>>
> >>> So when the customers buy a new nic for the host, the vendor manager
> >>> will plug a device to the host from the DPU.
> >> I understand once a customer orders a new NIC, you wants to present the NIC
> >> to the host.
> >> However you only owns the DPU and the customer owns the host, that means
> >> this creation and hot plug must be transparent to the host and there may not be
> >> a host driver help handling an interrupt/probe.
> >>
> > That is ok. when driver is loaded, it would query about its child devices and probe it, if we strictly want to follow SIOV model.
> >
> >> However this is not PCI which has a tree/switch and can enumerate devices to
> >> the host by spanning the device across the PCI hierarchy.
> >>
> > Those enumeration is triggered by the parent PCI device and pci bridge and switch will also discover it.
> >
> >> To address an ADI, there is only a device_id.
> >>
> > SIOV device must have a unique identifier at PCI bus level for sure.
> > I cannot speak more about it in this forum due to other logistics issue.
> > But assume that there is PCI level unique identifier for SIOV device that switches on the path will learn about.
> >
> >> So, do you mind share how your DPU offload the device model? What kind of
> >> device your DPU provide to the host? Lets see whether DPU can mediate this by
> >> its own?
> >>
> > It is a virtio nic, blk and other virtio devices for us.
> > A DPU hotplugs a device, host side either gets interrupt or later gets to know about it when explicitly queries.
> > There is no mediation per say here, it is just a dpu based SIOV device like a regular PF.
> >
> > For non virtio DPU device, I implemented them in Linux for dpus 2 years ago.
> > You might find a Linux reference model useful at [1].
> > A usage model already exists in one OS and in use for non virtio devices.
> > This certainly works without SIOV unique PCI device identifiers, because DPU (non-host) managed SIOV device spec still does not exist.
> >
> > For virtio, I think we should wait for this piece to be defined and leverage that, instead of virtio tc creating its own.
> >
> > [1] https://github.com/Mellanox/scalablefunctions/wiki
> well I see SF facing the similar challenge, I can add a command for the
> driver to query all existing SIOV ADIs of a device,
> and the device return ADIs id and status. Looks good? and work for you
> @Xuan?

Could I have your plan for this?

If you do not mind, I'd like to add a command to query VF's info. Such
as mac, ip, etc.

Thanks.



>
> Thanks
>