Re: [libvirt] RFC: Enable unprivileged SG_IO

Il 22/11/2012 15:11, Osier Yang ha scritto: > Hi, > > http://lwn.net/Articles/524720/ introduces new sysfs knob > (unpriv_sgio) for SCSI device to allow the unprivileged SG_IO. > > I don't have solid thought on how the libvirt interface should > be yet. It shouldn't be a XML entry of disk device, as the device > can be shared by multiple guests, and the configuration should > be kept same for all of them, having a XML entry for it will > make things a mess. > > What Paolo suggested is to add an entry in qemu.conf, just > like "cgroup_device_acl": > > sgio_device_acl = [ "/dev/sda" ] > > When libvirtd starting, set the sysfs knob "unpriv_sgio" of > the devices listed to 1, and 0 when libvirtd exists. > > I don't quite agree with this approach, as entries in qemu.conf > generally should be configuration for the whole qemu driver, > however, the SG_IO setting is at the device layer, or not > higher than guest layer. I don't like it either, but I don't see any alternative... > What I'm thinking about is to have a public API to tune the > knob independantly with domain/driver, that means it's up to > management apps to manage the knob's value, setting it to 1 > before domain(s) starting, and 0 when no domain is using it. At this point, it's simpler to just let the admin do this in /etc/rc.d/rc.local or in udev rules (which was my initial idea).