[Intel-gfx] [PATCH v4] drm/i915: Restore context and pd for ringbuffer submission after reset

[Chris Wilson]

On Tue, Feb 07, 2017 at 05:54:10PM +0200, Mika Kuoppala wrote:
> Chris Wilson <chris at chris-wilson.co.uk> writes:
> 
> > Following a reset, the context and page directory registers are lost.
> > However, the queue of requests that we resubmit after the reset may
> > depend upon them - the registers are restored from a context image, but
> > that restore may be inhibited and may simply be absent from the request
> > if it was in the middle of a sequence using the same context. If we
> > prime the CCID/PD registers with the first request in the queue (even
> > for the hung request), we prevent invalid memory access for the
> > following requests (and continually hung engines).
> >
> > v2: Magic BIT(8), reserved for future use but still appears unused.
> > v3: Some commentary on handling innocent vs guilty requests
> > v4: Add a wait for PD_BASE fetch. The reload appears to be instant on my
> > Ivybridge, but this bit probably exists for a reason.
> >
> > Fixes: 821ed7df6e2a ("drm/i915: Update reset path to fix incomplete requests")
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> > Cc: Mika Kuoppala <mika.kuoppala at intel.com>
> 
> Reviewed-by: Mika Kuoppala <mika.kuoppala at intel.com>

Thanks very much for the review, pushed as this fixes a reproducible
hang when combined with redundant MI_SET_CONTEXT elimination.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre