[libvirt] need custom /dev entries in LXC

[Michael R. Hines]

On 06/03/2013 06:03 AM, Daniel P. Berrange wrote:
> On Wed, May 22, 2013 at 06:22:12PM -0400, Michael R. Hines wrote:
>> Hi,
>>
>> We run nvidia devices inside libvirt-managed LXC containers.
>>
>> It used to be that simply doing:
>>
>> $ echo 'c 195:* rwm' > /sys/fs/cgroup/devices/libvirt/lxc
>>
>> Then, after booting the container, we would do:
>>
>> $ mknod -m 666 /dev/nvidia0 c 195 0
>>
>> .... would be good enough to run our CUDA applications.
>>
>> But, according to:
>>
>> $ cat src/lxc/lxc_container.c
>>
>> The CAP_MKNOD capability is being dropped and only a specific
>> set of devices is being created before booting the container.
>>
>> Is there any reason why this is not per-device configurable?
> With recent libvirt you can pass through arbitrary block and
> character devices explicitly, using the following XML:
>
>    http://libvirt.org/formatdomain.html#elementsHostDevCaps
>
> As such there is never any need to change cgroups or use
> mknod as you describe.
>
>
> Daniel

Thanks for the response, Daniel. That's good news.