[Intel-gfx] [PATCH 1/2] drm/i915: Allow DRM_ROOT_ONLY|DRM_MASTER to submit privileged batchbuffers

[Eric Anholt]

Chris Wilson <chris at chris-wilson.co.uk> writes:

> With the introduction of per-process GTT space, the hardware designers
> thought it wise to also limit the ability to write to MMIO space to only
> a "secure" batch buffer. The ability to rewrite registers is the only
> way to program the hardware to perform certain operations like scanline
> waits (required for tear-free windowed updates). So we either have a
> choice of adding an interface to perform those synchronized updates
> inside the kernel, or we permit certain processes the ability to write
> to the "safe" registers from within its command stream. This patch
> exposes the ability to submit a SECURE batch buffer to
> DRM_ROOT_ONLY|DRM_MASTER processes.

This seems like a major blow to ever getting non-root X.
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