From mboxrd@z Thu Jan  1 00:00:00 1970
From: Chris Wilson <chris@chris-wilson.co.uk>
Subject: Re: [PATCH 17/48] drm/i915: Track which ring a context
 ran on
Date: Fri, 18 Apr 2014 10:51:46 +0100
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To: Ben Widawsky <benjamin.widawsky@intel.com>
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On Fri, Dec 06, 2013 at 02:11:02PM -0800, Ben Widawsky wrote:
> From: Ben Widawsky <ben@bwidawsk.net>
> 
> Previously we dropped the association of a context to a ring. It is
> however very important to know which ring a context ran on (we could
> have reused the other member, but I was nitpicky).
> 
> This is very important when we switch address spaces, which unlike
> context objects, do change per ring.
> 
> As an example, if we have:
> 
>         RCS   BCS
> ctx            A
> ctx      A
> ctx      B
> ctx            B
> 
> Without tracking the last ring B ran on, we wouldn't know to switch the
> address space on BCS in the last row.
> 
> As a result, we no longer need to track which ring a context "belongs"
> to, as it never really made much sense anyway.

What about ring->last_context != to? That would force the update on BCS
from A to B.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre