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

Koenig, Christian Christian.Koenig at amd.com
Mon May 27 13:42:45 UTC 2019

Am 27.05.19 um 15:26 schrieb 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.

Yeah, completely agree to that. That's why I think we should not do this 
at all and just let Intel fix it's userspace bugs :P

Anyway my concern is really that we should stop extending functionality 
on the primary node.

E.g. the render node is for use by the clients and the primary node for 
mode setting and use by the display server only.


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

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