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

Jani Nikula
2015-04-30T10:35:01Z

On Wed, 15 Apr 2015, Daniel Vetter <daniel@ffwll.ch> wrote:
> On Wed, Apr 15, 2015 at 11:07:15AM +0100, Chris Wilson wrote:
>> 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).
>
> Yeah it's only interesting for hsw really.
>
>> > 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"
>
> Yeah not my best commit summary ever. I'll go with the first suggestion.

Pushed to drm-intel-next-queued as "drm/i915: Enable cmd parser to do
secure batch promotion for aliasing ppgtt", with

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=90190

and Mika's r-b. Thanks for the patch and review.

BR,
Jani.

> -Daniel
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
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--
Jani Nikula, Intel Open Source Technology Center