Re: [PATCH 12/17] drm/i915: Arm cmd parser with aliasng ppgtt only

Chris Wilson
2015-04-15T10:07:22Z

On Wed, Apr 15, 2015 at 11:43:25AM +0200, Daniel Vetter wrote:
> On Tue, Apr 14, 2015 at 07:10:30PM +0100, Chris Wilson wrote:
> > On Tue, Apr 14, 2015 at 05:35:22PM +0200, Daniel Vetter wrote:
> > > With the binding regression from the original full ppgtt patches
> > > fixed we can throw the switch. Yay!
> >
> > This changelog is misleading. The validation part of the command parser
> > has been running for some time, with people starting to notice the
> > performance regressions. What is being turned on here is the enabling
> > part to allow userspace to do more. So shouldn't that also be a bump in
> > the command parser version?
>
> mesa has independent checks that the register writes go through, so just
> switching the cmd parser to permission granting mode should be all that's
> neeeded really.

But the issue is the hardware would allow the writes anyway, and that
this patch has no actual effect since mesa can already do pipelined
register writes (at least on ivb/byt).

> And yes the cmd parser is enabled already, I thought "to arm" does convey
> that it's now going from dummy mode to live.

"Arm cmd parser" reads to me as a passive actor (parser is just a reader
and doesn't suggest that it enables anything).

"Enable cmd parser to do secure batch promotion for aliasing ppgtt"

or perhaps

"Now witness the firepower of this fully ARMED and OPERATIONAL cmdparser"
-Chris

--
Chris Wilson, Intel Open Source Technology Centre