[v5] drm/test: add a test suite for GEM objects backed by shmem

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 740c1c0bd068..b7abd436455f 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -74,12 +74,13 @@  config DRM_KUNIT_TEST_HELPERS
 
 config DRM_KUNIT_TEST
 	tristate "KUnit tests for DRM" if !KUNIT_ALL_TESTS
-	depends on DRM && KUNIT
+	depends on DRM && KUNIT && MMU
 	select DRM_BUDDY
 	select DRM_DISPLAY_DP_HELPER
 	select DRM_DISPLAY_HELPER
 	select DRM_EXEC
 	select DRM_EXPORT_FOR_TESTS if m
+	select DRM_GEM_SHMEM_HELPER
 	select DRM_KMS_HELPER
 	select DRM_KUNIT_TEST_HELPERS
 	select DRM_LIB_RANDOM
diff --git a/drivers/gpu/drm/tests/Makefile b/drivers/gpu/drm/tests/Makefile
index 2645af241ff0..d6183b3d7688 100644
--- a/drivers/gpu/drm/tests/Makefile
+++ b/drivers/gpu/drm/tests/Makefile
@@ -13,6 +13,7 @@  obj-$(CONFIG_DRM_KUNIT_TEST) += \
 	drm_format_helper_test.o \
 	drm_format_test.o \
 	drm_framebuffer_test.o \
+	drm_gem_shmem_test.o \
 	drm_managed_test.o \
 	drm_mm_test.o \
 	drm_modes_test.o \
diff --git a/drivers/gpu/drm/tests/drm_gem_shmem_test.c b/drivers/gpu/drm/tests/drm_gem_shmem_test.c
new file mode 100644
index 000000000000..91202e40cde9
--- /dev/null
+++ b/drivers/gpu/drm/tests/drm_gem_shmem_test.c
@@ -0,0 +1,383 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KUnit test suite for GEM objects backed by shmem buffers
+ *
+ * Copyright (C) 2023 Red Hat, Inc.
+ *
+ * Author: Marco Pagani <marpagan@redhat.com>
+ */
+
+#include <linux/dma-buf.h>
+#include <linux/iosys-map.h>
+#include <linux/sizes.h>
+
+#include <kunit/test.h>
+
+#include <drm/drm_device.h>
+#include <drm/drm_drv.h>
+#include <drm/drm_gem.h>
+#include <drm/drm_gem_shmem_helper.h>
+#include <drm/drm_kunit_helpers.h>
+
+#define TEST_SIZE		SZ_1M
+#define TEST_BYTE		0xae
+
+/*
+ * Wrappers to avoid an explicit type casting when passing action
+ * functions to kunit_add_action().
+ */
+static void kfree_wrapper(void *ptr)
+{
+	const void *obj = ptr;
+
+	kfree(obj);
+}
+
+static void sg_free_table_wrapper(void *ptr)
+{
+	struct sg_table *sgt = ptr;
+
+	sg_free_table(sgt);
+}
+
+static void drm_gem_shmem_free_wrapper(void *ptr)
+{
+	struct drm_gem_shmem_object *shmem = ptr;
+
+	drm_gem_shmem_free(shmem);
+}
+
+/*
+ * Test creating a shmem GEM object backed by shmem buffer. The test
+ * case succeeds if the GEM object is successfully allocated with the
+ * shmem file node and object functions attributes set, and the size
+ * attribute is equal to the correct size.
+ */
+static void drm_gem_shmem_test_obj_create(struct kunit *test)
+{
+	struct drm_device *drm_dev = test->priv;
+	struct drm_gem_shmem_object *shmem;
+
+	shmem = drm_gem_shmem_create(drm_dev, TEST_SIZE);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, shmem);
+	KUNIT_EXPECT_EQ(test, shmem->base.size, TEST_SIZE);
+	KUNIT_EXPECT_NOT_NULL(test, shmem->base.filp);
+	KUNIT_EXPECT_NOT_NULL(test, shmem->base.funcs);
+
+	drm_gem_shmem_free(shmem);
+}
+
+/*
+ * Test creating a shmem GEM object from a scatter/gather table exported
+ * via a DMA-BUF. The test case succeed if the GEM object is successfully
+ * created with the shmem file node attribute equal to NULL and the sgt
+ * attribute pointing to the scatter/gather table that has been imported.
+ */
+static void drm_gem_shmem_test_obj_create_private(struct kunit *test)
+{
+	struct drm_device *drm_dev = test->priv;
+	struct drm_gem_shmem_object *shmem;
+	struct drm_gem_object *gem_obj;
+	struct dma_buf buf_mock;
+	struct dma_buf_attachment attach_mock;
+	struct sg_table *sgt;
+	char *buf;
+	int ret;
+
+	/* Create a mock scatter/gather table */
+	buf = kunit_kzalloc(test, TEST_SIZE, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_NULL(test, buf);
+
+	sgt = kzalloc(sizeof(*sgt), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_NULL(test, sgt);
+
+	ret = kunit_add_action_or_reset(test, kfree_wrapper, sgt);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	ret = sg_alloc_table(sgt, 1, GFP_KERNEL);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	ret = kunit_add_action_or_reset(test, sg_free_table_wrapper, sgt);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	sg_init_one(sgt->sgl, buf, TEST_SIZE);
+
+	/* Init a mock DMA-BUF */
+	buf_mock.size = TEST_SIZE;
+	attach_mock.dmabuf = &buf_mock;
+
+	gem_obj = drm_gem_shmem_prime_import_sg_table(drm_dev, &attach_mock, sgt);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, gem_obj);
+	KUNIT_EXPECT_EQ(test, gem_obj->size, TEST_SIZE);
+	KUNIT_EXPECT_NULL(test, gem_obj->filp);
+	KUNIT_EXPECT_NOT_NULL(test, gem_obj->funcs);
+
+	/* The scatter/gather table will be freed by drm_gem_shmem_free */
+	kunit_remove_action(test, sg_free_table_wrapper, sgt);
+	kunit_remove_action(test, kfree_wrapper, sgt);
+
+	shmem = to_drm_gem_shmem_obj(gem_obj);
+	KUNIT_EXPECT_PTR_EQ(test, shmem->sgt, sgt);
+
+	drm_gem_shmem_free(shmem);
+}
+
+/*
+ * Test pinning backing pages for a shmem GEM object. The test case
+ * succeeds if a suitable number of backing pages are allocated, and
+ * the pages table counter attribute is increased by one.
+ */
+static void drm_gem_shmem_test_pin_pages(struct kunit *test)
+{
+	struct drm_device *drm_dev = test->priv;
+	struct drm_gem_shmem_object *shmem;
+	int i, ret;
+
+	shmem = drm_gem_shmem_create(drm_dev, TEST_SIZE);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, shmem);
+	KUNIT_EXPECT_NULL(test, shmem->pages);
+	KUNIT_EXPECT_EQ(test, shmem->pages_use_count, 0);
+
+	ret = kunit_add_action_or_reset(test, drm_gem_shmem_free_wrapper, shmem);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	ret = drm_gem_shmem_pin(shmem);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+	KUNIT_ASSERT_NOT_NULL(test, shmem->pages);
+	KUNIT_EXPECT_EQ(test, shmem->pages_use_count, 1);
+
+	for (i = 0; i < (shmem->base.size >> PAGE_SHIFT); i++)
+		KUNIT_ASSERT_NOT_NULL(test, shmem->pages[i]);
+
+	drm_gem_shmem_unpin(shmem);
+	KUNIT_EXPECT_NULL(test, shmem->pages);
+	KUNIT_EXPECT_EQ(test, shmem->pages_use_count, 0);
+}
+
+/*
+ * Test creating a virtual mapping for a shmem GEM object. The test
+ * case succeeds if the backing memory is mapped and the reference
+ * counter for virtual mapping is increased by one. Moreover, the test
+ * case writes and then reads a test pattern over the mapped memory.
+ */
+static void drm_gem_shmem_test_vmap(struct kunit *test)
+{
+	struct drm_device *drm_dev = test->priv;
+	struct drm_gem_shmem_object *shmem;
+	struct iosys_map map;
+	int ret, i;
+
+	shmem = drm_gem_shmem_create(drm_dev, TEST_SIZE);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, shmem);
+	KUNIT_EXPECT_NULL(test, shmem->vaddr);
+	KUNIT_EXPECT_EQ(test, shmem->vmap_use_count, 0);
+
+	ret = kunit_add_action_or_reset(test, drm_gem_shmem_free_wrapper, shmem);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	ret = drm_gem_shmem_vmap(shmem, &map);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+	KUNIT_ASSERT_NOT_NULL(test, shmem->vaddr);
+	KUNIT_ASSERT_FALSE(test, iosys_map_is_null(&map));
+	KUNIT_EXPECT_EQ(test, shmem->vmap_use_count, 1);
+
+	iosys_map_memset(&map, 0, TEST_BYTE, TEST_SIZE);
+	for (i = 0; i < TEST_SIZE; i++)
+		KUNIT_EXPECT_EQ(test, iosys_map_rd(&map, i, u8), TEST_BYTE);
+
+	drm_gem_shmem_vunmap(shmem, &map);
+	KUNIT_EXPECT_NULL(test, shmem->vaddr);
+	KUNIT_EXPECT_EQ(test, shmem->vmap_use_count, 0);
+}
+
+/*
+ * Test exporting a scatter/gather table of pinned pages suitable for
+ * PRIME usage from a shmem GEM object. The test case succeeds if a
+ * scatter/gather table large enough to accommodate the backing memory
+ * is successfully exported.
+ */
+static void drm_gem_shmem_test_get_pages_sgt(struct kunit *test)
+{
+	struct drm_device *drm_dev = test->priv;
+	struct drm_gem_shmem_object *shmem;
+	struct sg_table *sgt;
+	struct scatterlist *sg;
+	unsigned int si, len = 0;
+	int ret;
+
+	shmem = drm_gem_shmem_create(drm_dev, TEST_SIZE);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, shmem);
+
+	ret = kunit_add_action_or_reset(test, drm_gem_shmem_free_wrapper, shmem);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	ret = drm_gem_shmem_pin(shmem);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	sgt = drm_gem_shmem_get_sg_table(shmem);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, sgt);
+	KUNIT_EXPECT_NULL(test, shmem->sgt);
+
+	ret = kunit_add_action_or_reset(test, sg_free_table_wrapper, sgt);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	for_each_sgtable_sg(sgt, sg, si) {
+		KUNIT_EXPECT_NOT_NULL(test, sg);
+		len += sg->length;
+	}
+
+	KUNIT_EXPECT_GE(test, len, TEST_SIZE);
+}
+
+/*
+ * Test pinning pages and exporting a scatter/gather table suitable for
+ * driver usage from a shmem GEM object. The test case succeeds if the
+ * backing pages are pinned and a scatter/gather table large enough to
+ * accommodate the backing memory is successfully exported.
+ */
+static void drm_gem_shmem_test_get_sg_table(struct kunit *test)
+{
+	struct drm_device *drm_dev = test->priv;
+	struct drm_gem_shmem_object *shmem;
+	struct sg_table *sgt;
+	struct scatterlist *sg;
+	unsigned int si, ret, len = 0;
+
+	shmem = drm_gem_shmem_create(drm_dev, TEST_SIZE);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, shmem);
+
+	ret = kunit_add_action_or_reset(test, drm_gem_shmem_free_wrapper, shmem);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	/* The scatter/gather table will be freed by drm_gem_shmem_free */
+	sgt = drm_gem_shmem_get_pages_sgt(shmem);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, sgt);
+	KUNIT_ASSERT_NOT_NULL(test, shmem->pages);
+	KUNIT_EXPECT_EQ(test, shmem->pages_use_count, 1);
+	KUNIT_EXPECT_PTR_EQ(test, sgt, shmem->sgt);
+
+	for_each_sgtable_sg(sgt, sg, si) {
+		KUNIT_EXPECT_NOT_NULL(test, sg);
+		len += sg->length;
+	}
+
+	KUNIT_EXPECT_GE(test, len, TEST_SIZE);
+}
+
+/*
+ * Test updating the madvise state of a shmem GEM object. The test
+ * case checks that the function for setting madv updates it only if
+ * its current value is greater or equal than zero and returns false
+ * if it has a negative value.
+ */
+static void drm_gem_shmem_test_madvise(struct kunit *test)
+{
+	struct drm_device *drm_dev = test->priv;
+	struct drm_gem_shmem_object *shmem;
+	int ret;
+
+	shmem = drm_gem_shmem_create(drm_dev, TEST_SIZE);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, shmem);
+	KUNIT_ASSERT_EQ(test, shmem->madv, 0);
+
+	ret = kunit_add_action_or_reset(test, drm_gem_shmem_free_wrapper, shmem);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	ret = drm_gem_shmem_madvise(shmem, 1);
+	KUNIT_EXPECT_TRUE(test, ret);
+	KUNIT_ASSERT_EQ(test, shmem->madv, 1);
+
+	/* Set madv to a negative value */
+	ret = drm_gem_shmem_madvise(shmem, -1);
+	KUNIT_EXPECT_FALSE(test, ret);
+	KUNIT_ASSERT_EQ(test, shmem->madv, -1);
+
+	/* Check that madv cannot be set back to a positive value */
+	ret = drm_gem_shmem_madvise(shmem, 0);
+	KUNIT_EXPECT_FALSE(test, ret);
+	KUNIT_ASSERT_EQ(test, shmem->madv, -1);
+}
+
+/*
+ * Test purging a shmem GEM object. First, assert that a newly created
+ * shmem GEM object is not purgeable. Then, set madvise to a positive
+ * value and call drm_gem_shmem_get_pages_sgt() to pin and dma-map the
+ * backing pages. Finally, assert that the shmem GEM object is now
+ * purgeable and purge it.
+ */
+static void drm_gem_shmem_test_purge(struct kunit *test)
+{
+	struct drm_device *drm_dev = test->priv;
+	struct drm_gem_shmem_object *shmem;
+	struct sg_table *sgt;
+	int ret;
+
+	shmem = drm_gem_shmem_create(drm_dev, TEST_SIZE);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, shmem);
+
+	ret = kunit_add_action_or_reset(test, drm_gem_shmem_free_wrapper, shmem);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	ret = drm_gem_shmem_is_purgeable(shmem);
+	KUNIT_EXPECT_FALSE(test, ret);
+
+	ret = drm_gem_shmem_madvise(shmem, 1);
+	KUNIT_EXPECT_TRUE(test, ret);
+
+	/* The scatter/gather table will be freed by drm_gem_shmem_free */
+	sgt = drm_gem_shmem_get_pages_sgt(shmem);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, sgt);
+
+	ret = drm_gem_shmem_is_purgeable(shmem);
+	KUNIT_EXPECT_TRUE(test, ret);
+
+	drm_gem_shmem_purge(shmem);
+	KUNIT_EXPECT_NULL(test, shmem->pages);
+	KUNIT_EXPECT_NULL(test, shmem->sgt);
+	KUNIT_EXPECT_EQ(test, shmem->madv, -1);
+}
+
+static int drm_gem_shmem_test_init(struct kunit *test)
+{
+	struct device *dev;
+	struct drm_device *drm_dev;
+
+	/* Allocate a parent device */
+	dev = drm_kunit_helper_alloc_device(test);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, dev);
+
+	/*
+	 * The DRM core will automatically initialize the GEM core and create
+	 * a DRM Memory Manager object which provides an address space pool
+	 * for GEM objects allocation.
+	 */
+	drm_dev = __drm_kunit_helper_alloc_drm_device(test, dev, sizeof(*drm_dev),
+						      0, DRIVER_GEM);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, drm_dev);
+
+	test->priv = drm_dev;
+
+	return 0;
+}
+
+static struct kunit_case drm_gem_shmem_test_cases[] = {
+	KUNIT_CASE(drm_gem_shmem_test_obj_create),
+	KUNIT_CASE(drm_gem_shmem_test_obj_create_private),
+	KUNIT_CASE(drm_gem_shmem_test_pin_pages),
+	KUNIT_CASE(drm_gem_shmem_test_vmap),
+	KUNIT_CASE(drm_gem_shmem_test_get_pages_sgt),
+	KUNIT_CASE(drm_gem_shmem_test_get_sg_table),
+	KUNIT_CASE(drm_gem_shmem_test_madvise),
+	KUNIT_CASE(drm_gem_shmem_test_purge),
+	{}
+};
+
+static struct kunit_suite drm_gem_shmem_suite = {
+	.name = "drm_gem_shmem",
+	.init = drm_gem_shmem_test_init,
+	.test_cases = drm_gem_shmem_test_cases
+};
+
+kunit_test_suite(drm_gem_shmem_suite);
+
+MODULE_LICENSE("GPL");