Re: [libvirt] [PATCH 3/3] qemu: Forbid user aliases for USB controllers

On Fri, Mar 09, 2018 at 12:56:13 +0100, Michal Privoznik wrote: > https://bugzilla.redhat.com/show_bug.cgi?id=1552127 > > These are bit different than other devices. Their alias also > specify the name of the bus. For instance, if there are these > 'joined' USB devices: > > <controller type='usb' index='0' model='ich9-ehci1'> > <alias name='ua-myUSB'/> > <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x7'/> > </controller> > <controller type='usb' index='0' model='ich9-uhci1'> > <master startport='0'/> > <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0' multifunction='on'/> > </controller> > > which translates to cmd line as: > > -device ich9-usb-ehci1,id=ua-myUSB,bus=pci.0,addr=0x4.0x7 > -device ich9-usb-uhci1,masterbus=usb.0,firstport=0,bus=pci.0,multifunction=on,addr=0x4 > > The problem is that UHCI is still trying to serve 'usb.0' bus. > Rather than trying to come up with some complicated algorithm to > make everything work, lets forbid user aliases for USB > controllers. I'm not a fan of this. This creates situations where the user is not able to know which devices support user aliases and which don't. If there isn't a technical problem preventing this from working we should not forbid it.