From: "Dan Kenigsberg" <danken(a)redhat.com&gt; To: "Oved Ourfalli" <ovedo(a)redhat.com&gt;, "Dave Allan" <dallan(a)redhat.com&gt; Cc: "Dave Allan" <dallan(a)redhat.com&gt;, "Jiri Denemark" <jdenemar(a)redhat.com&gt;, "Michal Privoznik" <mprivozn(a)redhat.com&gt;, "Itamar Heim" <iheim(a)redhat.com&gt;, "Igor Lvovsky" <ilvovsky(a)redhat.com&gt;, "Eli Mesika" <emesika(a)redhat.com&gt;, "Hans de Goede" <hdegoede(a)redhat.com&gt;, "Andrew Cathrow" <acathrow(a)redhat.com&gt; Sent: Tuesday, May 8, 2012 11:41:25 AM Subject: Re: Supporting native USB in oVirt On Tue, May 08, 2012 at 03:19:32AM -0400, Oved Ourfalli wrote: > Hi, > > We are now working on adding the support for native USB devices on > oVirt. > As far as we understand, in order to use it we need to pass the > following devices with the following restrictions (according to > the EHCI spec): > 1. EHCI USB controller - with the highest function number, #7. > > devices='{type:controller,device:usb,model:ich9-ehci1,address:{type:pci,domain:0x0000,bus:0x00,slot:0x04,function:0x7}}' > > 2. 3 UHCI USB controllers, on the same bus and PCI slot as the EHCI > controller. Set the multifunction bit to on, on the controller > with function #0. > > devices='{type:controller,device:usb,model:ich9-uhci1,master:{startport:0},address:{type:pci,domain:0x0000,bus:0x00,slot:0x04,function:0x0,multifunction:on}}' > devices='{type:controller,device:usb,model:ich9-uhci2,master:{startport:2},address:{type:pci,domain:0x0000,bus:0x00,slot:0x04,function:0x1}}' > devices='{type:controller,device:usb,model:ich9-uhci3,master:{startport:4},address:{type:pci,domain:0x0000,bus:0x00,slot:0x04,function:0x2}}' I'd like to make it clear that the suggested API request Engine to pass a "master" attribute for the controller device, with a nested dictionary within. This makes sense, as I am certain that libvirt's modeling of the device has merits. However, AFAIK Engine does not do stuff like that at the momemnt.

> > 3. USB redirect devices (according to the needed number of USB > slots, maximum 6) on the same bus, each one having a different > port. > > devices='{type:redir,device:spicevmc,bus:usb,address:{type:usb,bus:0,port:1}}' > devices='{type:redir,device:spicevmc,bus:usb,address:{type:usb,bus:0,port:2}}' > devices='{type:redir,device:spicevmc,bus:usb,address:{type:usb,bus:0,port:3}}' > devices='{type:redir,device:spicevmc,bus:usb,address:{type:usb,bus:0,port:4}}' > devices='{type:redir,device:spicevmc,bus:usb,address:{type:usb,bus:0,port:5}}' > devices='{type:redir,device:spicevmc,bus:usb,address:{type:usb,bus:0,port:6}}' > > 4. If we want more than 6 USB slots, we need to have 2 EHCI > controllers, and 6 UHCI controllers, that are consistent with the > restrictions above, on different bus. > (we need them to be on different bus, since the connection between > the redirect devices and the controllers is the bus). > > According to Hans (cc-ed), if we let libvirt pick its own > addresses, it will put each controller of the composite USB > controller device on its own pci slot, which is a violation of the > EHCI spec. Is there an open libvirt bug for this? > > The problem is that the oVirt engine is not aware of addresses. > They aren't managed by it. > They are chosen automatically by libvirt, returned to the engine, > and they saved in the engine database in order to provide the > ability to retain the same PCI addresses after VM restart. Yes, we should be able to trust libvirt's assignement, certainly for the masses of VMs. Few VMs of certain customer may want to tweak the location of their devices. Maybe Engine does not need to expose this feature at the moment (I think it is better that each device address is considered a "blob" by Engine), but the Engine/Vdsm API should support that.

> > So, in order to support the EHCI spec, oVirt will have to be aware > of addresses, manage them (allocate them, check for collisions, > update on every libvirt change regarding that, etc...). Obviously, > it doesn't feel right, and in fact it is also not feasible, to > manage these addresses in the oVirt domain. That's not obvious to me. Engine could have a hard-coded addresses for the usb device gang. Libvirt could arrange the rest of the devices around it, so Engine should not worry about collisions. Libvirt's stable API relieves Engine from worrying about "every libvirt change regarding that" - it is libvirt responsibility to make sure that every future libvirt version would handle the USB addresses properly.

> > Is all the above correct, or are we missing something? > If so, can you address the issues above, and provide the ability to > manage these devices in libvirt? > > Regards, > Oved