Re: [igt-dev] [PATCH i-g-t 3/4] lib/igt_gt: Add compute engine

["Dixit, Ashutosh" <ashutosh.dixit@intel.com>]

+Jason for this thoughts.

On Fri, 22 Oct 2021 05:07:41 -0700, Tvrtko Ursulin wrote:
> On 22/10/2021 05:40, Zbigniew Kempczyński wrote:
> > On Thu, Oct 21, 2021 at 05:29:50PM -0700, Dixit, Ashutosh wrote:
> >> On Thu, 21 Oct 2021 17:12:26 -0700, Dixit, Ashutosh wrote:
> >>>
> >>> On Thu, 21 Oct 2021 00:33:21 -0700, Zbigniew Kempczyński wrote:
> >>>>
> >>>> On Thu, Oct 21, 2021 at 10:05:07AM +0530, priyanka.dandamudi@intel.com wrote:
> >>>>> From: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
> >>>>>
> >>>>> Add compute (CCS) engine. Add this to the IGT
> >>>>> structure to allow gem tests to execute.
> >>>>>
> >>>>> Signed-off-by: Stuart Summers <stuart.summers@intel.com>
> >>>>> Signed-off-by: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
> >>>>> Signed-off-by: Priyanka Dandamudi <priyanka.dandamudi@intel.com>
> >>>>> Cc: Ashutosh Dixit <ashutosh.dixit@intel.com>
> >>>>> Cc: Arjun Melkaveri <arjun.melkaveri@intel.com>
> >>>>> ---
> >>>>>   lib/igt_gt.c | 4 ++++
> >>>>>   1 file changed, 4 insertions(+)
> >>>>>
> >>>>> diff --git a/lib/igt_gt.c b/lib/igt_gt.c
> >>>>> index a0ba04cc..80fb65ca 100644
> >>>>> --- a/lib/igt_gt.c
> >>>>> +++ b/lib/igt_gt.c
> >>>>> @@ -604,6 +604,10 @@ const struct intel_execution_engine2 intel_execution_engines2[] = {
> >>>>>		{ "vcs1", I915_ENGINE_CLASS_VIDEO, 1, I915_EXEC_BSD | I915_EXEC_BSD_RING2 },
> >>>>>		{ "vcs2", I915_ENGINE_CLASS_VIDEO, 2, -1 },
> >>>>>		{ "vecs0", I915_ENGINE_CLASS_VIDEO_ENHANCE, 0, I915_EXEC_VEBOX },
> >>>>> +	{ "ccs0", I915_ENGINE_CLASS_COMPUTE, 0 , -1},
> >>>>> +	{ "ccs1", I915_ENGINE_CLASS_COMPUTE, 1 , -1},
> >>>>> +	{ "ccs2", I915_ENGINE_CLASS_COMPUTE, 2 , -1},
> >>>>> +	{ "ccs3", I915_ENGINE_CLASS_COMPUTE, 3 , -1},
> >>>
> >>> Is this correct? Isn't intel_execution_engines2 a list of just the legacy
> >>> engines? I don't think compute engines (which may vary in number) can be
> >>> added to the list of legacy engines. Isn't it true that compute engines can
> >>> only be accessed by querying the present engines dynamically (using
> >>> something like intel_ctx_create_all_physical())?
> >>
> >> I've copied Tvrtko (the boss :), but I am pretty sure what I said is
> >> correct. Legacy engines are what context 0 is created with (without adding
> >> any more engines onto context 0). So unless we can confirm that these
> >> engines are present for context 0 in the kernel we can't add them in IGT.
> >
> > I'm sorry, you're right. I wasn't aware legacy engines are "frozen", so
> > context 0 won't get an access to ccs. My r-b is incorrect then and patch
> > shouldn't land.  Another problem you've just realized me is with above
> > patch I would still need to detect ccs somehow on context 0 depending
> > on gen to allow iterator to go over existing engines.
>
> Don't know any longer guys - in the past "static engines" iterator was
> supposed to be used to enumerate all possible engines _without_ querying
> the device (like when enumerating subtests it isn't allowed to open the
> device).
>
> As such CCS would go to intel_execution_engines2 with "-1" for flags, as
> above patch had it. In other words in the past it was supposed to contain
> all engines i915 engine query could possibly return. The array would then
> also be used from elsewhere in the code to map class and instance to name
> and similar.
>
> Whether or not all this changed in the intel_ctx_t rewrite I have no
> idea. I see the "legacy" comment was added in:
>
> commit 9b32262bfadffffcde33c18ffb7c5292fbf4901e
> Author: Jason Ekstrand <jason@jlekstrand.net>
> Date:   Thu Apr 15 12:42:53 2021 -0500
>
>     docs: Add gem_engine_topology.h to the docs
>
> So perhaps ask Jason what was the plan there.
>
> Regards,
>
> Tvrtko