On 14/05/2022 00:06, Jordan Justen
wrote:
On 2022-05-13 05:31:00, Lionel Landwerlin wrote:On 02/05/2022 17:15, Ramalingam C wrote: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@xxxxxxxxx> cc: Matthew Auld <matthew.auld@xxxxxxxxx> cc: Thomas Hellstrom <thomas.hellstrom@xxxxxxxxxxxxxxx> cc: Daniel Vetter <daniel.vetter@xxxxxxxx> cc: Jon Bloomfield <jon.bloomfield@xxxxxxxxx> cc: Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx> cc: Kenneth Graunke <kenneth@xxxxxxxxxxxxx> cc: mesa-dev@xxxxxxxxxxxxxxxxxxxxx cc: Jordan Justen <jordan.l.justen@xxxxxxxxx> cc: Tony Ye <tony.ye@xxxxxxxxx> Reviewed-by: Matthew Auld <matthew.auld@xxxxxxxxx> --- 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.I think it's fine to assume Flat-CSS surface will always be in lmem. I see no issue for the Anv Vulkan driver. Maybe Nanley or Ken can speak for the Iris GL driver?Acked-by: Jordan Justen <jordan.l.justen@xxxxxxxxx> I think Nanley has accounted for this on iris with: https://gitlab.freedesktop.org/mesa/mesa/-/commit/42a865730ef72574e179b56a314f30fdccc6cba8 -Jordan
Thanks Jordan,
We might want to through in an additional : assert((flags
& BO_ALLOC_SMEM) == 0); in the CCS case
-Lionel
