Re: [Intel-gfx] [PATCH 2/9] drm/i915/perf: Add helper to check supported OA engines

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

On Tue, 14 Feb 2023 16:54:12 -0800, Umesh Nerlige Ramappa wrote:
>
> Add helper to check for supported OA engines.
>
> Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_perf.c | 19 ++++++++++++++++---
>  1 file changed, 16 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
> index 393a0da8b7c8..a879ae4bf8d7 100644
> --- a/drivers/gpu/drm/i915/i915_perf.c
> +++ b/drivers/gpu/drm/i915/i915_perf.c
> @@ -1570,6 +1570,19 @@ free_noa_wait(struct i915_perf_stream *stream)
>	i915_vma_unpin_and_release(&stream->noa_wait, 0);
>  }
>
> +static bool engine_supports_oa(const struct intel_engine_cs *engine)
> +{
> +	enum intel_platform platform = INTEL_INFO(engine->i915)->platform;
> +
> +	if (intel_engine_is_virtual(engine))
> +		return false;

Let's move this check to a different (or a separate) patch (with
explanation about OA and virtual engines in case of separate patch). It is
strange to see this check in this patch since previously we have only
supported render (I think there is only a single render engine so no
virtual render engines are possible, correct?).

With the changes above this is:

Reviewed-by: Ashutosh Dixit <ashutosh.dixit@intel.com>

Is there anything intrinsically wrong with virtual engines that we cannot
get OA data for them? Since we get OA data from an OA unit not engines so
wondering why this restriction. So if I have a virtual engine consisting of
two VDBOX engines attached to a single OAM unit we cannot get OA data for
this virtual engine?

Or is just that we haven't handled such cases? In that case it is fine to
disallow virtual engines till we can support them. Sorry just trying to
understand the restriction.