[libvirt] Changing device owner

Alex Williamson alex.williamson at redhat.com
Sat Jul 30 14:32:53 UTC 2011

On Sat, 2011-07-30 at 17:19 +0300, Shahar Havivi wrote:
> On 30.07.11 07:20, Alex Williamson wrote:
> > On Sat, 2011-07-30 at 12:12 +0300, Shahar Havivi wrote:
> > > Alex,
> > > 
> > > Regarding vdsm changing a device owner,
> > > Last time I asked in #virt for using usb device in vdsm hook in
> > > /dev/bus/usb/<addr> I was told that vdsm should change the owner to qemu:kvm.
> > > So for the sr-iov device /sys/bus/pci/devices/<addr>/resource*, rom, and reset 
> > > libvirt should change the owner and not vdsm?
> > 
> > I'm not in any position to say who should do what between vdsm and
> > libvirt.  However, the end result for device assignment to work with an
> > unprivileged guest is that someone needs to change file ownership on
> > those pci sysfs files before qemu is launched or before devices are hot
> > added to a guest.  libvirt does this for a purely libvirt managed guest.
> > In the example we saw yesterday, nobody was doing it.  Thanks,
> > 
> > Alex
> Ok,
> as far as I know vdsm need to change its devices.
> in our sr-iov example you change the reset and the resource* owner, did you
> change any other file?

No, and I don't think the "resource" file is necessary, the default read
access should be sufficient.  We need resource[0-5], rom, and reset (any
given device will likely only implement a subset of these).  We also
access config, but that happens via the pre-opened file descriptor.


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