Capture the impact of memory region preference list of the objects, on their memory residency and Flat-CCS capability.
v2: Fix the Flat-CCS capability of an obj with {lmem, smem} preference list [Thomas] v3: Reworded the doc [Matt]
Signed-off-by: Ramalingam C ramalingam.c@intel.com cc: Matthew Auld matthew.auld@intel.com cc: Thomas Hellstrom thomas.hellstrom@linux.intel.com cc: Daniel Vetter daniel.vetter@ffwll.ch cc: Jon Bloomfield jon.bloomfield@intel.com cc: Lionel Landwerlin lionel.g.landwerlin@intel.com cc: Kenneth Graunke kenneth@whitecape.org cc: mesa-dev@lists.freedesktop.org cc: Jordan Justen jordan.l.justen@intel.com cc: Tony Ye tony.ye@intel.com Reviewed-by: Matthew Auld matthew.auld@intel.com --- include/uapi/drm/i915_drm.h | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h index a2def7b27009..b7e1c2fe08dc 100644 --- a/include/uapi/drm/i915_drm.h +++ b/include/uapi/drm/i915_drm.h @@ -3443,6 +3443,22 @@ struct drm_i915_gem_create_ext { * At which point we get the object handle in &drm_i915_gem_create_ext.handle, * along with the final object size in &drm_i915_gem_create_ext.size, which * should account for any rounding up, if required. + * + * Note that userspace has no means of knowing the current backing region + * for objects where @num_regions is larger than one. The kernel will only + * ensure that the priority order of the @regions array is honoured, either + * when initially placing the object, or when moving memory around due to + * memory pressure + * + * On Flat-CCS capable HW, compression is supported for the objects residing + * in I915_MEMORY_CLASS_DEVICE. When such objects (compressed) has other + * memory class in @regions and migrated (by I915, due to memory + * constrain) to the non I915_MEMORY_CLASS_DEVICE region, then I915 needs to + * decompress the content. But I915 dosen't have the required information to + * decompress the userspace compressed objects. + * + * So I915 supports Flat-CCS, only on the objects which can reside only on + * I915_MEMORY_CLASS_DEVICE regions. */ struct drm_i915_gem_create_ext_memory_regions { /** @base: Extension link. See struct i915_user_extension. */