[RFC PATCH 07/42] drm/i915/region: support volatile objects

[Matthew Auld <matthew.auld@intel.com>]

Volatile objects are marked as DONTNEED while pinned, therefore once
unpinned the backing store can be discarded.

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Abdiel Janulgue <abdiel.janulgue@linux.intel.com>
---
 drivers/gpu/drm/i915/i915_gem_object.h        |  3 +-
 drivers/gpu/drm/i915/intel_memory_region.c    | 10 +++-
 .../drm/i915/selftests/intel_memory_region.c  | 54 +++++++++++++++++++
 3 files changed, 65 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_object.h b/drivers/gpu/drm/i915/i915_gem_object.h
index efc23fc2b1df..0dfe9603e3cc 100644
--- a/drivers/gpu/drm/i915/i915_gem_object.h
+++ b/drivers/gpu/drm/i915/i915_gem_object.h
@@ -164,7 +164,8 @@ struct drm_i915_gem_object {
 	 */
 #define I915_BO_ACTIVE_REF 0
 #define I915_BO_ALLOC_CONTIGUOUS (1<<1)
-#define I915_BO_ALLOC_FLAGS (I915_BO_ALLOC_CONTIGUOUS)
+#define I915_BO_ALLOC_VOLATILE   (1<<2)
+#define I915_BO_ALLOC_FLAGS (I915_BO_ALLOC_CONTIGUOUS | I915_BO_ALLOC_VOLATILE)
 
 	/*
 	 * Is the object to be mapped as read-only to the GPU
diff --git a/drivers/gpu/drm/i915/intel_memory_region.c b/drivers/gpu/drm/i915/intel_memory_region.c
index ed37599c7784..5531ed94bdab 100644
--- a/drivers/gpu/drm/i915/intel_memory_region.c
+++ b/drivers/gpu/drm/i915/intel_memory_region.c
@@ -148,6 +148,9 @@ i915_memory_region_get_pages_buddy(struct drm_i915_gem_object *obj)
 
 	i915_sg_trim(st);
 
+	if (flags & I915_BO_ALLOC_VOLATILE)
+		obj->mm.madv = I915_MADV_DONTNEED;
+
 	__i915_gem_object_set_pages(obj, st, sg_page_sizes);
 
 	return 0;
@@ -209,7 +212,12 @@ i915_gem_object_create_region(struct intel_memory_region *mem,
 	obj->flags = flags;
 
 	mutex_lock(&mem->obj_lock);
-	list_add(&obj->region_link, &mem->objects);
+
+	if (flags & I915_BO_ALLOC_VOLATILE)
+		list_add(&obj->region_link, &mem->purgeable);
+	else
+		list_add(&obj->region_link, &mem->objects);
+
 	mutex_unlock(&mem->obj_lock);
 
 	i915_gem_object_set_cache_coherency(obj, obj->cache_level);
diff --git a/drivers/gpu/drm/i915/selftests/intel_memory_region.c b/drivers/gpu/drm/i915/selftests/intel_memory_region.c
index fbb1497d0f82..0f6432a2a4c4 100644
--- a/drivers/gpu/drm/i915/selftests/intel_memory_region.c
+++ b/drivers/gpu/drm/i915/selftests/intel_memory_region.c
@@ -309,12 +309,66 @@ static int igt_mock_continuous(void *arg)
 	return err;
 }
 
+static int igt_mock_volatile(void *arg)
+{
+	struct intel_memory_region *mem = arg;
+	struct drm_i915_gem_object *obj;
+	int err;
+
+	obj = i915_gem_object_create_region(mem, PAGE_SIZE, 0);
+	if (IS_ERR(obj))
+		return PTR_ERR(obj);
+
+	err = i915_gem_object_pin_pages(obj);
+	if (err)
+		goto err_put;
+
+	i915_gem_object_unpin_pages(obj);
+
+	err = i915_gem_shrink_memory_region(mem, PAGE_SIZE);
+	if (err != -ENOSPC) {
+		pr_err("shrink memory region\n");
+		goto err_put;
+	}
+
+	obj = i915_gem_object_create_region(mem, PAGE_SIZE, I915_BO_ALLOC_VOLATILE);
+	if (IS_ERR(obj))
+		return PTR_ERR(obj);
+
+	if (!(obj->flags & I915_BO_ALLOC_VOLATILE)) {
+		pr_err("missing flags\n");
+		goto err_put;
+	}
+
+	err = i915_gem_object_pin_pages(obj);
+	if (err)
+		goto err_put;
+
+	i915_gem_object_unpin_pages(obj);
+
+	err = i915_gem_shrink_memory_region(mem, PAGE_SIZE);
+	if (err) {
+		pr_err("failed to shrink memory\n");
+		goto err_put;
+	}
+
+	if (i915_gem_object_has_pages(obj)) {
+		pr_err("object pages not discarded\n");
+		err = -EINVAL;
+	}
+
+err_put:
+	i915_gem_object_put(obj);
+	return err;
+}
+
 int intel_memory_region_mock_selftests(void)
 {
 	static const struct i915_subtest tests[] = {
 		SUBTEST(igt_mock_fill),
 		SUBTEST(igt_mock_shrink),
 		SUBTEST(igt_mock_continuous),
+		SUBTEST(igt_mock_volatile),
 	};
 	struct intel_memory_region *mem;
 	struct drm_i915_private *i915;
-- 
2.20.1

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