[PATCH 01/13] drm/amdgpu: introduce and honour DRM_FORCE_AUTH workaround

[Emil Velikov]

On 2019/05/27, Daniel Vetter wrote:
> On Mon, May 27, 2019 at 10:47:39AM +0000, Koenig, Christian wrote:
> > Am 27.05.19 um 10:17 schrieb Emil Velikov:
> > > From: Emil Velikov <emil.velikov at collabora.com>
> > >
> > > Currently one can circumvent DRM_AUTH, when the ioctl is exposed via the
> > > render node. A seemingly deliberate design decision.
> > >
> > > Hence we can drop the DRM_AUTH all together (details in follow-up patch)
> > > yet not all userspace checks if it's authenticated, but instead uses
> > > uncommon assumptions.
> > >
> > > After days of digging through git log and testing, only a single (ab)use
> > > was spotted - the Mesa RADV driver, using the AMDGPU_INFO ioctl and
> > > assuming that failure implies lack of authentication.
> > >
> > > Affected versions are:
> > >   - the whole 18.2.x series, which is EOL
> > >   - the whole 18.3.x series, which is EOL
> > >   - the 19.0.x series, prior to 19.0.4
> > 
> > Well you could have saved your time, cause this is still a NAK.
> > 
> > For the record: I strongly think that we don't want to expose any render 
> > functionality on the primary node.
> > 
> > To even go a step further I would say that at least on AMD hardware we 
> > should completely disable DRI2 for one of the next generations.
> > 
> > As a follow up I would then completely disallow the DRM authentication 
> > for amdgpu, so that the command submission interface on the primary node 
> > can only be used by the display server.
> 
> So amdgpu is running in one direction, while everyone else is running in
> the other direction? Please note that your patch to change i915 landed
> already, so that ship is sailing (but we could ofc revert that back
> again).
> 
> Imo really not a great idea if we do a amdgpu vs. everyone else split
> here. If we want to deprecate dri2/flink/rendering on primary nodes across
> the stack, then that should be a stack wide decision, not an amdgpu one.
> 
Cannot agree more - I would love to see drivers stay consistent.

Fwiw, this series consistently paves the way toward nuking DRM_AUTH ;-)

Thanks
Emil