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Subject: Re: [RFC PATCH v2 1/2] Add virtio Admin Virtqueue specification
On Sat, Jul 31, 2021 at 02:34:25PM +0300, Max Gurtovoy wrote: > > On 7/30/2021 10:05 AM, Cornelia Huck wrote: > > On Thu, Jul 29 2021, Max Gurtovoy <mgurtovoy@nvidia.com> wrote: > > > > > On 7/28/2021 3:48 PM, Michael S. Tsirkin wrote: > > > > On Mon, Jul 26, 2021 at 07:52:53PM +0300, Max Gurtovoy wrote: > > > > > +\subsubsection{Vendor specific command set}\label{sec:Basic Facilities of a Virtio Device / Admin Virtqueues / Admin command set / Vendor specific command set} > > > > > + > > > > > +The Vendor specific command set is a group of classes and commands > > > > > +within each of these classes which are vendor specific. Refer to > > > > > +each vendor specification for more information on the supported > > > > > +commands. > > > > Here's another example. > > > > It's important that there is a way to make a device completely > > > > generic without vendor specific expensions. > > > > Would be hard to do here. > > > > > > > > That's a generic comment. > > > > > > > > but specifically I am very reluctant to add vendor specific stuff like > > > > this directly in the spec. We already have VIRTIO_PCI_CAP_VENDOR_CFG > > > > and if that is not sufficient I would like to know why > > > > before we add more vendor specific stuff. > > > We are adding an option to add vendor specific commands. We're not > > > adding it to the spec since each vendor will have its own manual for > > > that. > > IMHO, that way madness lies. I want to be able to look at the spec and > > be able to implement a compliant device or a compliant driver. If a > > vendor has some special feature they want to support, put it in the > > spec, so that it is possible to actually implement it. > > You can implement a compliant device and a compliant. why do you think you > can't ? > > Some features are vendor/sub-vendor specific. > > And as mentioned, you already added it to the spec so I guess it was for a > reason. Well we basically just reserved a capability ID so if people add their vendor specific ones they don't conflict with each other or capabilities we'll add in the future. And such a capability can prove useful for things like identifying the device to enable workarounds, etc. That is a far cry from a fat interface which generic drivers will need to support and who's sole purpose is vendor specific extensions. And yes, it also allows you to unload the generic driver and load a vendor driver. Which can then go wild if it wants to - nothing we can or want to do about it. > If someone would like to add its special souse to virtio device and we have > a flexible admin queue to manage it with a spec compliant manner, why not ? > > The feature might not get support by the working group so do you really want > to limit vendor from implementing features that are not agreed here on the > mailing list ? > > Adding a vendor specific command set is trivial. Supporting all this mess leter isn't. So we better make sure just how is all this vendor stuff going to be limited. > > > > > For example, we can use virtio-cli to pass command from command line to > > > device in pass-through manner without changing driver. > > Things like that are part of the driver as in the spec sense. The spec > > does not care how you actually split the implementation, or what > > controls you are giving to whom. We need a defined interface. > > We have an interface. Its the admin queue. > > Virtio-cli will be a user space tool to send commands via this admin queue > and configure the device. > > The driver will just open a char dev to supply a channel to this admin queue > from user space. > > Examples: > > 1. format a virtio-blk device to add data integrity checks (T-10) > > 2. set 5 msix to VF_1, 12 msix to VF_2 and 2 msix to VF_3 before enabling > SRIOV > > 3. Get telemetry log > > 4. Get error log > > 5. Get vendor specific HW health report > > 6. Get generic virtio device health report > > 7. set 5 queues to VF_1, 12 queues to VF_2 and 2 queues to VF_3 before > enabling SRIOV > > > This knowledge is needed for the sys-admin and not the driver. The driver > will provide the channel to enable this configuration by an > orchestrator/admin. > > > > >
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