[Intel-gfx] [PATCH v3] drm/i915: check that rpm ref is held when accessing ringbuf in stolen mem

[Chris Wilson]

On Wed, Jan 27, 2016 at 03:43:49PM +0000, daniele.ceraolospurio at intel.com wrote:
> From: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
> 
> While running some tests on the scheduler patches with rpm enabled I
> came across a corruption in the ringbuffer, which was root-caused to
> the GPU being suspended while commands were being emitted to the
> ringbuffer. The access to memory was failing because the GPU needs to
> be awake when accessing stolen memory (where my ringbuffer was located).
> Since we have this constraint it looks like a sensible idea to check
> that we hold a refcount when we access the rungbuffer.
> 
> v2: move the check from ring_begin to ringbuffer iomap time (Chris)
> v3: update comment (Chris)
> 
> Cc: John Harrison <John.C.Harrison at Intel.com>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>

That explains itself nicely, thanks.
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>

It also rings alarms bells for intel_fbdev.c
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre