Commit f28d4266 authored by Chris Wilson's avatar Chris Wilson Committed by Matthew Auld
Browse files

drm/i915/gt: Move scratch page into system memory on all platforms 



The scratch page should never be accessed, and is only assigned as a
filler page to redirection invalid userspace access. It is not of a
performance concern and so we prefer to have a single consistent
configuration across all platforms, reducing the pressure on device
memory and avoiding the direct device access that would be required to
initialise the scratch page.

Signed-off-by: default avatarChris Wilson <chris.p.wilson@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: default avatarMatthew Auld <matthew.auld@intel.com>
Signed-off-by: default avatarMatthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220926155018.109678-1-matthew.auld@intel.com
parent e5cedf98

drivers/gpu/drm/i915/gt/gen8_ppgtt.c

+22 −21
Original line number Diff line number Diff line
@@ -929,8 +929,10 @@ struct i915_ppgtt *gen8_ppgtt_create(struct intel_gt *gt, 
	 */

	ppgtt->vm.has_read_only = !IS_GRAPHICS_VER(gt->i915, 11, 12);



	if (HAS_LMEM(gt->i915)) {

	if (HAS_LMEM(gt->i915))

		ppgtt->vm.alloc_pt_dma = alloc_pt_lmem;

	else

		ppgtt->vm.alloc_pt_dma = alloc_pt_dma;



	/*

	 * On some platforms the hw has dropped support for 4K GTT pages
@@ -941,17 +943,16 @@ struct i915_ppgtt *gen8_ppgtt_create(struct intel_gt *gt, 
	 * 4K GTT pages for SMEM objects, we can't have a "normal" 4K

	 * page-table with scratch pointing to LMEM, since that's

	 * undefined from the hw pov. The simplest solution is to just

		 * move the 64K scratch page to SMEM on such platforms and call

	 * move the 64K scratch page to SMEM on all platforms and call

	 * it a day, since that should work for all configurations.

	 *

	 * Using SMEM instead of LMEM has the additional advantage of

	 * not reserving high performance memory for a "never" used

	 * filler page. It also removes the device access that would

	 * be required to initialise the scratch page, reducing pressure

	 * on an even scarcer resource.

	 */

		if (HAS_64K_PAGES(gt->i915))

	ppgtt->vm.alloc_scratch_dma = alloc_pt_dma;

		else

			ppgtt->vm.alloc_scratch_dma = alloc_pt_lmem;

	} else {

		ppgtt->vm.alloc_pt_dma = alloc_pt_dma;

		ppgtt->vm.alloc_scratch_dma = alloc_pt_dma;

	}



	ppgtt->vm.pte_encode = gen8_pte_encode;