[libvirt] [PATCH] qemu: Allow /dev/dri/renderD128

[Michal Privoznik]

On 02/08/2017 11:16 AM, Daniel P. Berrange wrote:
> On Wed, Feb 08, 2017 at 10:44:53AM +0100, Michal Privoznik wrote:
>> On 02/08/2017 10:31 AM, Daniel P. Berrange wrote:
>>> On Wed, Feb 08, 2017 at 10:26:26AM +0100, Michal Privoznik wrote:
>>>> This demand comes from qemu_egl_rendernode_open() in qemu source
>>>> code. It is needed for virgl to work with qemu:///system
>>>> connection. The session one works just fine.
>>>>
>>>> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
>>>> ---
>>>>  docs/drvqemu.html.in               | 1 +
>>>>  src/qemu/qemu.conf                 | 3 ++-
>>>>  src/qemu/qemu_cgroup.c             | 1 +
>>>>  src/qemu/test_libvirtd_qemu.aug.in | 1 +
>>>>  4 files changed, 5 insertions(+), 1 deletion(-)
>>>
>>>> diff --git a/src/qemu/qemu_cgroup.c b/src/qemu/qemu_cgroup.c
>>>> index 6c90d46d1..b47f714fc 100644
>>>> --- a/src/qemu/qemu_cgroup.c
>>>> +++ b/src/qemu/qemu_cgroup.c
>>>> @@ -47,6 +47,7 @@ const char *const defaultDeviceACL[] = {
>>>>      "/dev/random", "/dev/urandom",
>>>>      "/dev/ptmx", "/dev/kvm", "/dev/kqemu",
>>>>      "/dev/rtc", "/dev/hpet", "/dev/vfio/vfio",
>>>> +    "/dev/dri/renderD128",
>>>
>>> Surely this is only needed in very specific scenarios. ie with
>>> the virtio-vga 3d rendering enabled.
>>>
>>> Allowing unconditional access to the DRI devices is a big
>>> wide open door from security POV, for something few VMs
>>> will ever need.
>>>
>>> The global device whitelist is only for devices that we
>>> expect every QEMU to unconditionally require.
>>
>> I can argue the same about /dev/vfio/vfio and yet we have it on the list.
> 
> I consider that to be a bug we should fix too. It should only ever have
> been added if the guest is actually using vfio.

Agreed. So just to be clear on the design, if we automatically enable
/dev/vfio/vfio in devices cgroup on domain startup (of course only for
domains that are doing pci passtrhough^Wassignment), you would be okay
with that?
Similarly, allowing /dev/dri/renderD128 for domains with virgl on their
startup.

Michal