[Intel-gfx] [PATCH 8/8] drm/i915: Allow user to set cache at BO creation

[Jordan Justen]

On 2023-04-20 09:11:18, Yang, Fei wrote:
> > On 20/04/2023 12:39, Andi Shyti wrote:
> >> Hi Fei,
> >>
> >>> To comply with the design that buffer objects shall have immutable
> >>> cache setting through out their life cycle, {set, get}_caching ioctl's
> >>> are no longer supported from MTL onward. With that change caching
> >>> policy can only be set at object creation time. The current code
> >>> applies a default (platform dependent) cache setting for all objects.
> >>> However this is not optimal for performance tuning. The patch extends
> >>> the existing gem_create uAPI to let user set PAT index for the object
> >>> at creation time.
> >>> The new extension is platform independent, so UMD's can switch to using
> >>> this extension for older platforms as well, while {set, get}_caching are
> >>> still supported on these legacy paltforms for compatibility reason.
> >>>
> >>> Cc: Chris Wilson <chris.p.wilson at linux.intel.com>
> >>> Cc: Matt Roper <matthew.d.roper at intel.com>
> >>> Cc: Andi Shyti <andi.shyti at linux.intel.com>
> >>> Signed-off-by: Fei Yang <fei.yang at intel.com>
> >>> Reviewed-by: Andi Shyti <andi.shyti at linux.intel.com>
> >>
> >> because this is an API change, we need some more information
> >> here.
> >>
> >> First of all you need to CC the userspace guys that have been
> >> working on top of your series and get their ack's.
> >
> > Yes, and a link to a Mesa merge request which uses the uapi should be
> > included.
> 
> Working with Mesa team on this, stay tuned.
> 

I would like to see the extension detection issue is handled before
ack'ing this.

How about a new DRM_I915_QUERY_GEM_CREATE_EXTENSIONS item, that
returns a u64 array of usable extension names for
DRM_IOCTL_I915_GEM_CREATE_EXT?

A similar DRM_I915_QUERY_GEM_CONTEXT_CREATE_EXTENSIONS could also
provide an alternative to Alan's "drm/i915/uapi/pxp: Add a GET_PARAM
for PXP", and more easily allow advertising future new extensions for
context/buffer creation.

-Jordan