Re: [virtio-comment] Re: [RFC PATCH] admin-queue: bind the group member to the device

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

On Mon, 26 Jun 2023 05:32:47 -0400, "Michael S. Tsirkin" <mst@redhat.com> wrote:
> On Mon, Jun 26, 2023 at 02:22:10PM +0800, Xuan Zhuo wrote:
> > The VFs of the SR-IOV are created by the user inside the guest OS, so the virtio
> > devices don't know about these VFs. Because each VF may be assigned a different role
> > by the user, the virtio device can not choose one VF to bind random.
> > So only the user knows how to bind the virtio devices to the VFs.
> > On the other hand, generally the virtio devices are not created by the user
> > inside the guest OS. This requires some management platform to participate.
> >
> > So the usage of this command:
> > 1. The user purchases a virtio network card on the management platform,
> >    and sets the ip, queue number, etc. The user obtains the identity of
> >    the network card.
> > 2. The user creates a VF with echo 8 > sriov_numvfs
>
> this one is unlikely, as this requires PF access and affects all VFs.

How do you create VFs?

>
> > 3. The user binds the net crad to a VF with identity through the command
> >    of the patch
> >
> > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
>
>
>
>
> > ---
> >  admin.tex | 41 ++++++++++++++++++++++++++++++++++++++++-
> >  1 file changed, 40 insertions(+), 1 deletion(-)
> >
> > diff --git a/admin.tex b/admin.tex
> > index 2efd4d7..64d0667 100644
> > --- a/admin.tex
> > +++ b/admin.tex
> > @@ -115,7 +115,8 @@ \subsection{Group administration commands}\label{sec:Basic Facilities of a Virti
> >  \hline \hline
> >  0x0000 & VIRTIO_ADMIN_CMD_LIST_QUERY & Provides to driver list of commands supported for this group type    \\
> >  0x0001 & VIRTIO_ADMIN_CMD_LIST_USE & Provides to device list of commands used for this group type \\
> > -0x0002 - 0x7FFF & - & Commands using \field{struct virtio_admin_cmd}    \\
> > +0x0002 & VIRTIO_ADMIN_CMD_BIND_DEVICE & Bind the device to one group member \\
> > +0x0003 - 0x7FFF & - & Commands using \field{struct virtio_admin_cmd}    \\
> >  \hline
> >  0x8000 - 0xFFFF & - & Reserved for future commands (possibly using a different structure)    \\
> >  \hline
> > @@ -429,6 +430,44 @@ \subsection{Group administration commands}\label{sec:Basic Facilities of a Virti
> >  \field{VF Enable} refer to registers within the SR-IOV Extended
> >  Capability as specified by \hyperref[intro:PCIe]{[PCIe]}.
> >
> > +\subsubsection{Bind the device for member}
> > +
> > +The VFs of the SR-IOV are created by the user inside the guest OS, so the virtio
> > +devices don't know about these VFs.
>
> I don't really get how.

Maybe there is something wrong with my expression. The backend can know these
vfs, but it doesn't know which vf should be bound to which backend.

>
> > Because each VF may be assigned a different role
> > +by the user, the virtio device can not choose one VF to bind random.
> > +So only the user knows how to bind the virtio devices to the VFs.
> > +On the other hand, generally the virtio devices are not created by the user
> > +inside the guest OS. This requires some management platform to participate.
> > +
> > +So we introduce a new admin queue command to bind the VFs and the virtio
> > +devices.
>
> This description needs a complete rewrite, but to try to help you I'd
> need to figure out what is being said. My guess is that this is an
> attempt to introduce some kind of identity to VFs.  OK but what is this

NO. An identity for the device in the backend.

> identity and how is it better than using VF#?  You want it to persist
> when NumVFs in the SR-IOV capability changes?
>
> > +\begin{lstlisting}
> > +struct virtio_admin_cmd_bind {
> > +    u64 identity;
> > +};
> > +\end{lstlisting}
> > +
> > +The user got the \field{identity} from the management platform, that is not
> > +included by this spec.
>
> Without even understanding the above, what I don't like about this
> proposal, is that it assumes some out of band interface to either
> specify or discover these IDs.

This is an rfc, and I actually don't like this proposal too. But I want to raise
this issue, this is a real problem, and I hope to find a standardized solution.
I don't want us to create a private solution internally.

Thanks.

> With admin commands we now have
> ability to fully specify a management interface, and I'd rather
> we had a complete proposal covering all aspects of it.
> If some platform does not want to use the management aspects,
> that's ok.
>
> > +
> > +\drivernormative{\paragraph}{Group administration commands}{Basic Facilities of a Virtio Device / Device groups / Group administration commands / Bind the device for member}
> > +
> > +VIRTIO_ADMIN_CMD_BIND_DEVICE requires that the \field{group_member_id} MUST be set.
> > +
> > +The \field{identity} is passed by the user. It is the identity of the virtio
> > +device.
> > +
> > +\devicenormative{\paragraph}{Group administration commands}{Basic Facilities of a Virtio Device / Device groups / Group administration commands / Bind the device for member}
> > +
> > +Every device MUST have one unique \field{identity} in the host.
> > +
> > +If the PF device can not find the device by the \field{identity},
> > +the \field{status} MUST be set to VIRTIO_ADMIN_STATUS_EINVAL.
> > +
> > +If the device is found by the \field{identity}, the device MUST work as the
> > +device of this group member specified by the \field{group_member_id}.
> > +
> >  \section{Administration Virtqueues}\label{sec:Basic Facilities of a Virtio Device / Administration Virtqueues}
> >
> >  An administration virtqueue of an owner device is used to submit
>
> > --
> > 2.32.0.3.g01195cf9f
>
>
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