On Mon, Dec 14, 2015 at 05:13:43PM +0000, Chris Wilson wrote:
> On Mon, Dec 14, 2015 at 04:30:04PM +0000, Nick Hoath wrote:
> > diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
> > index 900ffd0..7df3c7a 100644
> > --- a/drivers/gpu/drm/i915/i915_gem_context.c
> > +++ b/drivers/gpu/drm/i915/i915_gem_context.c
> > @@ -431,17 +431,22 @@ void i915_gem_context_fini(struct drm_device *dev)
> > i915_gem_object_ggtt_unpin(dctx->legacy_hw_ctx.rcs_state);
> > }
> >
> > - for (i = 0; i < I915_NUM_RINGS; i++) {
> > + for (i = I915_NUM_RINGS; --i >= 0;) {
> > struct intel_engine_cs *ring = &dev_priv->ring[i];
> >
> > if (ring->last_context)
> > i915_gem_context_unreference(ring->last_context);
> >
> > - ring->default_context = NULL;
> > ring->last_context = NULL;
> > }
> >
> > i915_gem_context_unreference(dctx);
> > +
> > + for (i = I915_NUM_RINGS; --i >= 0;) {
> > + struct intel_engine_cs *ring = &dev_priv->ring[i];
> > +
> > + ring->default_context = NULL;
> > + }
> > }
>
> Why?
Ok, as you say intel_lrc needs to iterate over all rings to look at the
default context in context_free. Feels odd, and breaks the onion of
context_init / context_fini. The pecularity is in lrc and I would push
the oddness back there.
That engine->default_context is pinned and mapped is only because of the
HWS and for no other reason does it exist (seqno writes are to address
not relative the per-context HWS index). You could simply allocate a
page for each engine and use that as the global HWS irrespective of
contexts.
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
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