RenderThread unauthenticated DRM ioctl

[Francois Gervais]

Hi,

We are trying to enable the i915 acceleration on Android-x86.

It works fine except that RenderThread is doing unauthentication ioctl calls so it gets refused by the kernel.

Here are some of the calls that gets refused with a bit of custom debug output to see why it got so:

[   18.680047] [drm:drm_ioctl] pid=2504, name=RenderThread, dev=0xe200, auth=0, I915_GEM_EXECBUFFER2

[   18.680052] drm_ioctl_permit(476): flags = 0x21

[   18.680056] drm_ioctl_permit(477): drm_is_render_client(file_priv) = 0

[   18.680061] drm_ioctl_permit(478): file_priv->authenticated = 0

[   18.680811] [drm:drm_ioctl] pid=2504, name=RenderThread, dev=0xe200, auth=0, I915_GEM_BUSY

[   18.680814] drm_ioctl_permit(476): flags = 0x21

[   18.680818] drm_ioctl_permit(477): drm_is_render_client(file_priv) = 0

[   18.680821] drm_ioctl_permit(478): file_priv->authenticated = 0

[   18.692584] [drm:drm_ioctl] pid=2504, name=RenderThread, dev=0xe200, auth=0, DRM_IOCTL_GEM_OPEN

[   18.692588] drm_ioctl_permit(476): flags = 0x11

[   18.692590] drm_ioctl_permit(477): drm_is_render_client(file_priv) = 0

[   18.692593] drm_ioctl_permit(478): file_priv->authenticated = 0

This is the kernel condition that refuses it:

/* AUTH is only for authenticated or render client */

if (unlikely((flags & DRM_AUTH) && !drm_is_render_client(file_priv) &&

    !file_priv->authenticated))

return -EACCES;

If we forcefully accept, the 3d acceleration works.

Any idea?

[Povilas Staniulis]

This is normal.
Android x86 kernel is patched to disable drm_ioctl_permit checks.

What kernel are you running this on ?

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[youling 257]

https://github.com/maurossi/linux/commit/02b34c31f733d35306a6e49e28625144ac0e66bc

[Francois Gervais]

Ah that explains it, we run a vanilla 4.8.11 kernel.

Thanks a lot for pointing that out.