[Intel-gfx] [PATCH v2] drm/i915: Assert that the context-switch completion matches our context

[Chris Wilson]

On Mon, Jan 23, 2017 at 10:26:15AM +0000, Tvrtko Ursulin wrote:
> 
> On 23/01/2017 08:50, Chris Wilson wrote:
> >When execlists signals the context completion, it also provides the
> >context id for the status event. Assert that id matches the one we expect.
> >
> >v2: The upper dword of the context status is a duplicate of the upper
> >dword from elsp submission (i.e. includes the group id as well as the
> >context id). Include this check as well.
> >
> >Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> >Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> >---
> > drivers/gpu/drm/i915/intel_lrc.c | 6 ++++++
> > 1 file changed, 6 insertions(+)
> >
> >diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> >index 432ee495dec2..963b1888d8a0 100644
> >--- a/drivers/gpu/drm/i915/intel_lrc.c
> >+++ b/drivers/gpu/drm/i915/intel_lrc.c
> >@@ -595,6 +595,12 @@ static void intel_lrc_irq_handler(unsigned long data)
> > 			if (!(status & GEN8_CTX_STATUS_COMPLETED_MASK))
> > 				continue;
> >
> >+			/* Check the context/desc id for this event matches */
> >+			GEM_BUG_ON(((readl(buf + 2 * idx + 1) & (MAX_CONTEXT_HW_ID-1)) !=
> >+				    port[0].request->ctx->hw_id));
> >+			GEM_BUG_ON(readl(buf + 2 * idx + 1) !=
> >+				   upper_32_bits(port[0].request->ctx->engine[engine->id].lrc_desc));
> >+
> 
> Not sure that you need the first line since the lrc_desc includes
> the hw_id? Or perhaps you don't need the second one since lrc_desc
> is built from hw_id? :)

It was defense in depth :)

The first line is certain, that make sure the event matches
port[0].request.

The second line makes sure that everything matches my understanding, and
that lrc_desc is correct (or vice versa).
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre