Re: [PATCH] gem_pin: Be explicit about GGTT needs

[Ben Widawsky <ben@bwidawsk.net>]

On Thu, Nov 07, 2013 at 07:54:59PM +0100, Daniel Vetter wrote:
> On Thu, Nov 7, 2013 at 7:46 PM, Ben Widawsky <ben@bwidawsk.net> wrote:
> > On Thu, Nov 07, 2013 at 07:36:50PM +0100, Daniel Vetter wrote:
> >> On Thu, Nov 7, 2013 at 7:11 PM, Ben Widawsky <ben@bwidawsk.net> wrote:
> >> >> > @@ -63,7 +65,7 @@ static void exec(int fd, uint32_t handle, uint32_t offset)
> >> >> >     gem_exec[0].relocs_ptr = (uintptr_t) gem_reloc;
> >> >> >     gem_exec[0].alignment = 0;
> >> >> >     gem_exec[0].offset = 0;
> >> >> > -   gem_exec[0].flags = 0;
> >> >> > +   gem_exec[0].flags = LOCAL__EXEC_OBJ_NEEDS_GTT;
> >> >>
> >> >> This only really works with the aliasing ppgtt stuff on gen6, I'd just
> >> >> skip the test -it's not really useful with real ppgtt.
> >> >> -Daniel
> >> >
> >> > It is really useful with real ppgtt. Please rethink your assertion.
> >>
> >> The test links up the global gtt used by the current pin ioctl with
> >> the ppgtt. That's not useful, except when they alias. If we want
> >> soft-pinning, then we need a new ioctl mode to return the right
> >> address from the right address space. Which means a new (sub)test.
> >> -Daniel
> >
> > This is only indirectly related to soft pinning. No context will ever have the
> > global GTT address space. If you want to support the pin IOCTL, (which
> > Chris has before said he requires - the original patch series disabled
> > it) you must do this. We already have a flag that does what we want,
> > and, demonstrably, a test which exercises it.
> >
> > I do not think a new ioctl, nor a new subtest is the solution for this.
> 
> Ok, I'll wait until I see the code that implements this on top of
> ppgtt. But until we have that I don't think we need to change the test
> at all.
> -Daniel

This is a question for Chris. If DDX only depends on the behavior with
aliasing PPGTT, then I agree - no test change needed.

-- 
Ben Widawsky, Intel Open Source Technology Center