[RFC PATCH 6/6] drm/gma500: Add software-only KUnit coverage for SGX page tables

[Gabriel Gama <operatingsystemsdepression@gmail.com>]

Add KUnit cases for invalid ranges and tiles, the final GPU page,
directory crossings, PFN limits, collision rollback and removal holes.

The optional built-in fixture uses a software page directory with no DRM
device and hw_context=-1. It performs no MMIO or GPU submission.

Signed-off-by: Gabriel Gama <operatingsystemsdepression@gmail.com>

---
 drivers/gpu/drm/gma500/Kconfig    |  10 ++
 drivers/gpu/drm/gma500/Makefile   |   2 +
 drivers/gpu/drm/gma500/mmu_test.c | 222 ++++++++++++++++++++++++++++++
 3 files changed, 234 insertions(+)
 create mode 100644 drivers/gpu/drm/gma500/mmu_test.c

diff --git a/drivers/gpu/drm/gma500/Kconfig b/drivers/gpu/drm/gma500/Kconfig
index dc4c56638..b6e2dda13 100644
--- a/drivers/gpu/drm/gma500/Kconfig
+++ b/drivers/gpu/drm/gma500/Kconfig
@@ -16,3 +16,13 @@ config DRM_GMA500
 	  Say yes for an experimental 2D KMS framebuffer driver for the
 	  Intel GMA500 (Poulsbo), Intel GMA600 (Moorestown/Oak Trail) and
 	  Intel GMA3600/3650 (Cedar Trail).
+
+config DRM_GMA500_KUNIT_TEST
+	bool "KUnit tests for the GMA500 SGX page tables" if !KUNIT_ALL_TESTS
+	depends on DRM_GMA500=y && KUNIT=y
+	default KUNIT_ALL_TESTS
+	help
+	  Run software-only tests for SGX page-table range validation,
+	  rollback, mapping collisions and removal. The tests use a software
+	  page directory with no device or hardware context, and never
+	  submit commands to the GPU or access its registers.
diff --git a/drivers/gpu/drm/gma500/Makefile b/drivers/gpu/drm/gma500/Makefile
index 58fed80c7..069400d70 100644
--- a/drivers/gpu/drm/gma500/Makefile
+++ b/drivers/gpu/drm/gma500/Makefile
@@ -39,4 +39,6 @@ gma500_gfx-y += \
 gma500_gfx-$(CONFIG_ACPI) +=  opregion.o
 gma500_gfx-$(CONFIG_DRM_FBDEV_EMULATION) +=  fbdev.o
 
+gma500_gfx-$(CONFIG_DRM_GMA500_KUNIT_TEST) += mmu_test.o
+
 obj-$(CONFIG_DRM_GMA500) += gma500_gfx.o
diff --git a/drivers/gpu/drm/gma500/mmu_test.c b/drivers/gpu/drm/gma500/mmu_test.c
new file mode 100644
index 000000000..0581c7d9a
--- /dev/null
+++ b/drivers/gpu/drm/gma500/mmu_test.c
@@ -0,0 +1,222 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* SGX page-table tests. No device, hardware context, or MMIO is required. */
+#include <kunit/test.h>
+#include <linux/highmem.h>
+
+#include "mmu.h"
+#include "psb_drv.h"
+
+struct psb_mmu_test_context {
+	struct psb_mmu_driver driver;
+	struct psb_mmu_pd *pd;
+	struct page *pages[4];
+};
+
+static int psb_mmu_test_init(struct kunit *test)
+{
+	struct psb_mmu_test_context *ctx;
+	int i;
+
+	ctx = kunit_kzalloc(test, sizeof(*ctx), GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+	test->priv = ctx;
+	spin_lock_init(&ctx->driver.lock);
+	init_rwsem(&ctx->driver.sem);
+	ctx->pd = psb_mmu_alloc_pd(&ctx->driver, 1, 0);
+	if (!ctx->pd)
+		return -ENOMEM;
+	for (i = 0; i < ARRAY_SIZE(ctx->pages); i++) {
+		ctx->pages[i] = alloc_page(GFP_DMA32);
+		if (!ctx->pages[i]) {
+			while (i--)
+				__free_page(ctx->pages[i]);
+			psb_mmu_free_pagedir(ctx->pd);
+			return -ENOMEM;
+		}
+	}
+	return 0;
+}
+
+static void psb_mmu_test_exit(struct kunit *test)
+{
+	struct psb_mmu_test_context *ctx = test->priv;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(ctx->pages); i++)
+		__free_page(ctx->pages[i]);
+	psb_mmu_free_pagedir(ctx->pd);
+}
+
+static u32 psb_mmu_test_pte(struct psb_mmu_pd *pd, u32 address)
+{
+	struct psb_mmu_pt *pt = pd->tables[address >> PSB_PDE_SHIFT];
+	u32 *entries;
+	u32 value;
+
+	if (!pt)
+		return pd->invalid_pte;
+	entries = kmap_local_page(pt->p);
+	value = entries[(address >> PAGE_SHIFT) & 0x3ff];
+	kunmap_local(entries);
+	return value;
+}
+
+static void psb_mmu_zero_pages_test(struct kunit *test)
+{
+	struct psb_mmu_test_context *ctx = test->priv;
+
+	KUNIT_EXPECT_EQ(test, psb_mmu_insert_pages(ctx->pd, NULL, 0, 0,
+						   0, 0, 0), 0);
+	KUNIT_EXPECT_EQ(test, psb_mmu_insert_pfn_sequence(ctx->pd, 0,
+							  0, 0, 0), 0);
+	psb_mmu_remove_pages(ctx->pd, 0, 0, 0, 0);
+	psb_mmu_remove_pfn_sequence(ctx->pd, 0, 0);
+	KUNIT_EXPECT_PTR_EQ(test, ctx->pd->tables[0], NULL);
+}
+
+static void psb_mmu_range_test(struct kunit *test)
+{
+	struct psb_mmu_test_context *ctx = test->priv;
+
+	KUNIT_EXPECT_EQ(test, psb_mmu_insert_pages(ctx->pd, ctx->pages,
+						   1, 1, 0, 0, 0), -EINVAL);
+	KUNIT_EXPECT_EQ(test, psb_mmu_insert_pages(ctx->pd, ctx->pages,
+						   0xfffff000UL, 2, 0, 0, 0),
+			-ERANGE);
+	KUNIT_EXPECT_EQ(test, psb_mmu_insert_pages(ctx->pd, ctx->pages,
+						   0, 4, 0, 4, 0), -EINVAL);
+	KUNIT_EXPECT_EQ(test, psb_mmu_insert_pages(ctx->pd, ctx->pages,
+						   0, 4, 3, 4, 0), -EINVAL);
+	KUNIT_EXPECT_EQ(test, psb_mmu_insert_pages(ctx->pd, ctx->pages,
+						   0, 4, 2, 1, 0), -EINVAL);
+	KUNIT_EXPECT_EQ(test, psb_mmu_insert_pages(ctx->pd, ctx->pages,
+						   0, 4, 2, U32_MAX, 0), -ERANGE);
+	KUNIT_EXPECT_EQ(test, psb_mmu_insert_pages(ctx->pd, NULL,
+						   0, 1, 0, 0, 0), -EINVAL);
+	KUNIT_EXPECT_PTR_EQ(test, ctx->pd->tables[0], NULL);
+}
+
+static void psb_mmu_last_page_test(struct kunit *test)
+{
+	struct psb_mmu_test_context *ctx = test->priv;
+
+	KUNIT_ASSERT_EQ(test, psb_mmu_insert_pages(ctx->pd, ctx->pages,
+						   0xfffff000UL, 1, 0, 0, 0), 0);
+	KUNIT_EXPECT_EQ(test, psb_mmu_test_pte(ctx->pd, 0xfffff000),
+			(u32)(page_to_pfn(ctx->pages[0]) << PAGE_SHIFT) |
+			PSB_PTE_VALID);
+	psb_mmu_remove_pages(ctx->pd, 0xfffff000UL, 1, 0, 0);
+	KUNIT_EXPECT_PTR_EQ(test, ctx->pd->tables[1023], NULL);
+}
+
+static void psb_mmu_directory_boundary_test(struct kunit *test)
+{
+	struct psb_mmu_test_context *ctx = test->priv;
+
+	KUNIT_ASSERT_EQ(test, psb_mmu_insert_pages(ctx->pd, ctx->pages,
+						   0x3ff000, 2, 0, 0, 0), 0);
+	KUNIT_EXPECT_EQ(test, ctx->pd->tables[0]->count, 1U);
+	KUNIT_EXPECT_EQ(test, ctx->pd->tables[1]->count, 1U);
+	psb_mmu_remove_pages(ctx->pd, 0x3ff000, 2, 0, 0);
+	KUNIT_EXPECT_PTR_EQ(test, ctx->pd->tables[0], NULL);
+	KUNIT_EXPECT_PTR_EQ(test, ctx->pd->tables[1], NULL);
+}
+
+static void psb_mmu_collision_rollback_test(struct kunit *test)
+{
+	struct psb_mmu_test_context *ctx = test->priv;
+	u32 retained;
+
+	KUNIT_ASSERT_EQ(test, psb_mmu_insert_pages(ctx->pd, ctx->pages + 3,
+						   0x400000, 1, 0, 0, 0), 0);
+	retained = psb_mmu_test_pte(ctx->pd, 0x400000);
+	KUNIT_EXPECT_EQ(test, psb_mmu_insert_pages(ctx->pd, ctx->pages,
+						   0x3ff000, 2, 0, 0, 0), -EBUSY);
+	KUNIT_EXPECT_PTR_EQ(test, ctx->pd->tables[0], NULL);
+	KUNIT_EXPECT_EQ(test, psb_mmu_test_pte(ctx->pd, 0x400000), retained);
+	KUNIT_EXPECT_EQ(test, ctx->pd->tables[1]->count, 1U);
+}
+
+static void psb_mmu_tiled_rollback_test(struct kunit *test)
+{
+	struct psb_mmu_test_context *ctx = test->priv;
+	u32 retained;
+
+	KUNIT_ASSERT_EQ(test, psb_mmu_insert_pages(ctx->pd, ctx->pages + 3,
+						   0x8000, 1, 0, 0, 0), 0);
+	retained = psb_mmu_test_pte(ctx->pd, 0x8000);
+	KUNIT_EXPECT_EQ(test, psb_mmu_insert_pages(ctx->pd, ctx->pages,
+						   0x3000, 4, 2, 4, 0), -EBUSY);
+	KUNIT_EXPECT_EQ(test, psb_mmu_test_pte(ctx->pd, 0x3000), 0U);
+	KUNIT_EXPECT_EQ(test, psb_mmu_test_pte(ctx->pd, 0x4000), 0U);
+	KUNIT_EXPECT_EQ(test, psb_mmu_test_pte(ctx->pd, 0x7000), 0U);
+	KUNIT_EXPECT_EQ(test, psb_mmu_test_pte(ctx->pd, 0x8000), retained);
+	KUNIT_EXPECT_EQ(test, ctx->pd->tables[0]->count, 1U);
+}
+
+static void psb_mmu_pfn_range_test(struct kunit *test)
+{
+	struct psb_mmu_test_context *ctx = test->priv;
+
+	KUNIT_EXPECT_EQ(test, psb_mmu_insert_pfn_sequence(ctx->pd, 0x100000,
+							  0, 1, 0), -ERANGE);
+	KUNIT_EXPECT_EQ(test, psb_mmu_insert_pfn_sequence(ctx->pd, 0xfffff,
+							  0, 2, 0), -ERANGE);
+	KUNIT_ASSERT_EQ(test, psb_mmu_insert_pfn_sequence(ctx->pd, 0xfffff,
+							  0, 1, 0), 0);
+	KUNIT_EXPECT_EQ(test, psb_mmu_test_pte(ctx->pd, 0), 0xfffff001U);
+	psb_mmu_remove_pfn_sequence(ctx->pd, 0, 1);
+	KUNIT_EXPECT_PTR_EQ(test, ctx->pd->tables[0], NULL);
+}
+
+static void psb_mmu_pfn_rollback_test(struct kunit *test)
+{
+	struct psb_mmu_test_context *ctx = test->priv;
+	u32 retained;
+
+	KUNIT_ASSERT_EQ(test, psb_mmu_insert_pfn_sequence(ctx->pd, 0x100,
+							  0x400000, 1, 0), 0);
+	retained = psb_mmu_test_pte(ctx->pd, 0x400000);
+	KUNIT_EXPECT_EQ(test, psb_mmu_insert_pfn_sequence(ctx->pd, 0x200,
+							  0x3ff000, 2, 0), -EBUSY);
+	KUNIT_EXPECT_PTR_EQ(test, ctx->pd->tables[0], NULL);
+	KUNIT_EXPECT_EQ(test, psb_mmu_test_pte(ctx->pd, 0x400000), retained);
+	KUNIT_EXPECT_EQ(test, ctx->pd->tables[1]->count, 1U);
+}
+
+static void psb_mmu_remove_hole_test(struct kunit *test)
+{
+	struct psb_mmu_test_context *ctx = test->priv;
+
+	KUNIT_ASSERT_EQ(test, psb_mmu_insert_pages(ctx->pd, ctx->pages,
+						   0x1000, 1, 0, 0, 0), 0);
+	psb_mmu_remove_pages(ctx->pd, 0x2000, 1, 0, 0);
+	KUNIT_EXPECT_EQ(test, ctx->pd->tables[0]->count, 1U);
+	psb_mmu_remove_pages(ctx->pd, 0x1000, 1, 0, 0);
+	psb_mmu_remove_pfn_sequence(ctx->pd, 0x400000, 1);
+	KUNIT_EXPECT_PTR_EQ(test, ctx->pd->tables[0], NULL);
+	KUNIT_EXPECT_PTR_EQ(test, ctx->pd->tables[1], NULL);
+}
+
+static struct kunit_case psb_mmu_test_cases[] = {
+	KUNIT_CASE(psb_mmu_zero_pages_test),
+	KUNIT_CASE(psb_mmu_range_test),
+	KUNIT_CASE(psb_mmu_last_page_test),
+	KUNIT_CASE(psb_mmu_directory_boundary_test),
+	KUNIT_CASE(psb_mmu_collision_rollback_test),
+	KUNIT_CASE(psb_mmu_tiled_rollback_test),
+	KUNIT_CASE(psb_mmu_pfn_range_test),
+	KUNIT_CASE(psb_mmu_pfn_rollback_test),
+	KUNIT_CASE(psb_mmu_remove_hole_test),
+	{}
+};
+
+static struct kunit_suite psb_mmu_test_suite = {
+	.name = "psb_mmu",
+	.init = psb_mmu_test_init,
+	.exit = psb_mmu_test_exit,
+	.test_cases = psb_mmu_test_cases,
+};
+
+kunit_test_suite(psb_mmu_test_suite);