[PATCH 1/3] drm/i915: Reserve some kernel space per vm

[Nirmoy Das]

From: Jonathan Cavitt <jonathan.cavitt at intel.com>

Reserve a page in each vm for kernel space to use for things
such as workarounds.

Signed-off-by: Jonathan Cavitt <jonathan.cavitt at intel.com>
Suggested-by: Chris Wilson <chris.p.wilson at linux.intel.com>
Signed-off-by: Nirmoy Das <nirmoy.das at intel.com>
---
 drivers/gpu/drm/i915/gt/gen8_ppgtt.c | 6 ++++++
 drivers/gpu/drm/i915/gt/intel_gtt.h  | 1 +
 2 files changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/i915/gt/gen8_ppgtt.c b/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
index 9895e18df043..162acf501880 100644
--- a/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
+++ b/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
@@ -230,6 +230,7 @@ static void gen8_ppgtt_cleanup(struct i915_address_space *vm)
 				     gen8_pd_top_count(vm), vm->top);
 
 	free_scratch(vm);
+	drm_mm_remove_node(&vm->rsvd);
 }
 
 static u64 __gen8_ppgtt_clear(struct i915_address_space * const vm,
@@ -1011,6 +1012,11 @@ struct i915_ppgtt *gen8_ppgtt_create(struct intel_gt *gt,
 	ppgtt->vm.foreach = gen8_ppgtt_foreach;
 	ppgtt->vm.cleanup = gen8_ppgtt_cleanup;
 
+	ppgtt->vm.rsvd.start = ppgtt->vm.total - SZ_4K;
+	ppgtt->vm.rsvd.size = SZ_4K;
+	ppgtt->vm.rsvd.color = I915_COLOR_UNEVICTABLE;
+	GEM_BUG_ON(drm_mm_reserve_node(&ppgtt->vm.mm, &ppgtt->vm.rsvd));
+
 	err = gen8_init_scratch(&ppgtt->vm);
 	if (err)
 		goto err_put;
diff --git a/drivers/gpu/drm/i915/gt/intel_gtt.h b/drivers/gpu/drm/i915/gt/intel_gtt.h
index 346ec8ec2edd..ab38a158fc71 100644
--- a/drivers/gpu/drm/i915/gt/intel_gtt.h
+++ b/drivers/gpu/drm/i915/gt/intel_gtt.h
@@ -246,6 +246,7 @@ struct i915_address_space {
 	struct work_struct release_work;
 
 	struct drm_mm mm;
+	struct drm_mm_node rsvd;
 	struct intel_gt *gt;
 	struct drm_i915_private *i915;
 	struct device *dma;
-- 
2.41.0