[Libvir] RFC: format for mapping host devices to guest

I'm considering the problem of mapping host USB devices through to the guest as one of the 2 remaining bits of USB support needed (the other being the mapping disks through as USB mass storage). I have previously mentioned some ideas in this mail, though looking back on this I don't much like them https://www.redhat.com/archives/libvir-list/2007-March/msg00205.html Also, there was just the message about a desire to support mapping of PCI devices. The USB stuff I want todo with both Xen and QEMU. In Xen, USB device passthrough is based on: usbdevice=host:[bus id].[device id] eg usbdevice=host:003.001 Or usbdevice=host:[vendor id]:[product id] eg usbdevice=host:0483:2016 In QEMU, USB device passthrough is pretty much the same with command line args: -usbdevice host:[bus id].[device id] eg -usbdevice host:003.001 Or -usbdevice host:[vendor id]:[product id] eg -usbdevice host:0483:2016 Finally, in Xen, PCI device passthrough is done with pci=['pci device id',....] eg pci=['00:1f.3'] So we need some form of element under the <devices> section per device to map through. At minimum this will need the source device info. If we are to support unplugging of USB devices in QEMU it is neccessary to have the target device id - this is generated by QEMU when attaching the USB device. So to attach a device: <host bus='usb'> <source device="003.001"/> </host> Or <host bus='usb'> <source vendor='0483' product='2016'> </host> The first form is useful for live hotplug - where you know the exact device instance. The second form is useful for permanent config - you don't know what device id it'll have since it may be plugged into the host in any order. When splitting the XML back out, QEMU would fill in the target info giving us either: <host bus='usb'> <source dev='003.001'/> <target dev='001.005'/> </host> Or <host bus='usb'> <source vendor='0483' product='2016'/> <target dev='001.005'/> </host> This is suitable for giving to virDomainDetachDevice() - we use the target dev for the QEMU monitor 'usb-detach' command. Now PCI would be similar - no hotplug to worry about here though, and no need (or availability) or target info. So the XML would simply be <host bus='pci'> <source dev='00:1f.3'/> </host> NB I choose 'host' as the element name since we're basically giving the guest an arbitrary host device. My previous email had thought about calling it 'bus' but we're not really defining a bus in this context and there may very well be some scenario in the future where we do need to represent the concept of a 'bus' in the XML directly. Dan. -- |=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=| |=- Perl modules: http://search.cpan.org/~danberr/ -=| |=- Projects: http://freshmeat.net/~danielpb/ -=| |=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=|