[Intel-gfx] [PATCH 01/23] drm/i915: Move aliasing_ppgtt underneath its i915_ggtt

[Chris Wilson]

Quoting Chris Wilson (2019-07-24 10:37:19)
> Quoting Chris Wilson (2019-07-24 10:27:38)
> > Quoting Tvrtko Ursulin (2019-07-24 09:56:34)
> > > 
> > > On 23/07/2019 19:38, Chris Wilson wrote:
> > > > +static int __context_pin_ppgtt(struct intel_context *ce)
> > > >   {
> > > >       struct i915_address_space *vm;
> > > >       int err = 0;
> > > >   
> > > > -     vm = ctx->vm ?: &ctx->i915->mm.aliasing_ppgtt->vm;
> > > > +     vm = vm_alias(ce);
> > > >       if (vm)
> > > 
> > > Can't return NULL it seems. (Same below.)
> > 
> > Are you so sure?
> > 
> > ce->gem_context->vm is only !NULL if there is a full-ppgtt
> > &ggtt->alias->vm is only !NULL if there is an aliasing-ppgtt
> > 
> > There may be contexts with neither (gen4, gen5).
> 
> It's not until the next patch where we always set ce->vm will it be
> non-NULL. Point taken.

Except, we purposely replace the i915_ggtt ce->vm with its alias, which
may still be NULL. (Which is fine as that is perma-pinned and we don't
need to fiddle.)
-Chris