virtio — archive

[PATCH v10 00/10] Introduce device group and device management

From: Michael S. Tsirkin <[email protected]>
To: [email protected]
Date: Wed, 08 Mar 2023 11:51:00 -0000

On Wed, Mar 08, 2023 at 11:05:00AM +0100, Jiri Pirko wrote: > Tue, Mar 07, 2023 at 05:30:18PM CET, [email protected] wrote: > >On Tue, Mar 07, 2023 at 08:36:41AM +0100, Jiri Pirko wrote: > >> Hmm, if not for now, the future exension would not be so simple, I fear. > > > >Without knowing what it is I can't say. > > Yep, so basically you say, for other things if they appear, > let's introduce another queue type? If yes, sounds fair to me. Yes. For example I find it likely that live migration/failover support will require a queue where driver pre-adds buffers and then device supplies information as state changes. > > > > >> > >> > > >> >Passing commands to devices themselves is already covered in spec > >> >reasonably well though not in a generic way. > >> > >> You mean using the control queue, correct? > > > >Depends on the device type. network devices have a control queue, yes. > > > >> >From one of the patch description of this patchset I understand that you > >> cannot use control queue for this because control queue is > >> device-specific, yet group control is device-agnostic. > >> > >> My undestanding therefore was, that the admin queue you are introducing > >> serves as a generic carrier for device-agnostic commands, in parallel > >> for having control queue serving as a generic carrier of device-specific > >> commands. If this is not the case, I think it would be nice to describe > >> the exact monivation and scope of admin queue. > > > >Nope unfortunately. This queue is just a carrier for admin commands. > >admin commands are commands that talk to one device about other > >devices. There's clearly no mechanism in the spec to do that, > >so we plug this hole. > > Okay, in that case "admin" sounds a bit misleading as for me it > implicates that this is for "administration" of the device. Yet is is > for the administration of other devices (slaves). > > Perhaps there could be different term used to clarify? > Group leader virtqueue? > Group owner virtqueue? > Group master virtqueue? I used group administration virtqueue in a couple of places, just inconsistently. Good enough? > > > > > > > >> > >> > > >> >What we lack is passing commands about one device to another device. > >> >E.g. control VFs through PFs. > >> > >> Could you provide examples of such commands please? > > > >For example a common feature is to program a vlan and have device > >put a given VF inside this vlan. > > I don't follow entirely. The way how the VF is connected to network > should be ouf of the scope of this interface. The eswitch manager should > take care. What you say sounds awfully like the "ip vf" legacy > interface, which should not be considered here I believe. > > If PF would be the eswitch manager, there are other means to do network > programming, using eswitch port representors. But I don't think this is > the can of worms we want to open now. I don't think we have a usecase > for it currently. Am I wrong Parav? > > > > > > >In a virtualization scenario host controls this vlan programming giving > >the network a measure of protection from VFs. If a VF is passed through > >to a VM, IOMMU limits VFs to only access guest memory so host has to do > >this programming through a PF. > > Understood. This really looks like "ip vf" legacy. I strongly believe > it should not be supported. > > Any other commands you have in mind? > > > > > > > > > >> > >> >This is what groups do. > >> >But if we see more uses we can always add them. > >> > > >> > > >> >I'd rather avoid being too generic though. > >> > >> In that case, why not to avoid using generic terms and stay > >> "group-centric"? What I mean is: > >> "Administration Virtqueues" -> "Group Administration Virtqueues" > >> "struct virtio_admin_cmd" -> "struct virtio_group_admin_cmd" > >> > >> Etc. Helps to avoid confusion. > > > >Sure, I tried to do that but missed some opportunities. > >Will address. > > Cool. > > > > > >> > >> > > >> > > >> > > >> > > >> >> > >> >> >+than one administration virtqueue. > >> > >> > >> [...] > >> > > > > > >This publicly archived list offers a means to provide input to the > >OASIS Virtual I/O Device (VIRTIO) TC. > > > >In order to verify user consent to the Feedback License terms and > >to minimize spam in the list archive, subscription is required > >before posting. > > > >Subscribe: [email protected] > >Unsubscribe: [email protected] > >List help: [email protected] > >List archive: https://lists.oasis-open.org/archives/virtio-comment/ > >Feedback License: https://www.oasis-open.org/who/ipr/feedback_license.pdf > >List Guidelines: https://www.oasis-open.org/policies-guidelines/mailing-lists > >Committee: https://www.oasis-open.org/committees/virtio/ > >Join OASIS: https://www.oasis-open.org/join/ > >