[v8,4/5] iommufd/selftest: Add coverage for IOMMU_GET_HW_INFO ioctl

diff --git a/drivers/iommu/iommufd/iommufd_test.h b/drivers/iommu/iommufd/iommufd_test.h
index 258de2253b61..3f3644375bf1 100644
--- a/drivers/iommu/iommufd/iommufd_test.h
+++ b/drivers/iommu/iommufd/iommufd_test.h
@@ -100,4 +100,13 @@  struct iommu_test_cmd {
 };
 #define IOMMU_TEST_CMD _IO(IOMMUFD_TYPE, IOMMUFD_CMD_BASE + 32)
 
+/* Mock structs for IOMMU_DEVICE_GET_HW_INFO ioctl */
+#define IOMMU_HW_INFO_TYPE_SELFTEST	0xfeedbeef
+#define IOMMU_HW_INFO_SELFTEST_REGVAL	0xdeadbeef
+
+struct iommu_test_hw_info {
+	__u32 flags;
+	__u32 test_reg;
+};
+
 #endif
diff --git a/drivers/iommu/iommufd/selftest.c b/drivers/iommu/iommufd/selftest.c
index 9223ff3f23f9..90e7c5400282 100644
--- a/drivers/iommu/iommufd/selftest.c
+++ b/drivers/iommu/iommufd/selftest.c
@@ -131,6 +131,21 @@  static struct iommu_domain mock_blocking_domain = {
 	.ops = &mock_blocking_ops,
 };
 
+static void *mock_domain_hw_info(struct device *dev, u32 *length, u32 *type)
+{
+	struct iommu_test_hw_info *info;
+
+	info = kzalloc(sizeof(*info), GFP_KERNEL);
+	if (!info)
+		return ERR_PTR(-ENOMEM);
+
+	info->test_reg = IOMMU_HW_INFO_SELFTEST_REGVAL;
+	*length = sizeof(*info);
+	*type = IOMMU_HW_INFO_TYPE_SELFTEST;
+
+	return info;
+}
+
 static struct iommu_domain *mock_domain_alloc(unsigned int iommu_domain_type)
 {
 	struct mock_iommu_domain *mock;
@@ -290,6 +305,7 @@  static struct iommu_device *mock_probe_device(struct device *dev)
 static const struct iommu_ops mock_ops = {
 	.owner = THIS_MODULE,
 	.pgsize_bitmap = MOCK_IO_PAGE_SIZE,
+	.hw_info = mock_domain_hw_info,
 	.domain_alloc = mock_domain_alloc,
 	.capable = mock_domain_capable,
 	.set_platform_dma_ops = mock_domain_set_plaform_dma_ops,
diff --git a/tools/testing/selftests/iommu/iommufd.c b/tools/testing/selftests/iommu/iommufd.c
index 8acd0af37aa5..a068bfbe9f83 100644
--- a/tools/testing/selftests/iommu/iommufd.c
+++ b/tools/testing/selftests/iommu/iommufd.c
@@ -113,6 +113,7 @@  TEST_F(iommufd, cmd_length)
 	}
 
 	TEST_LENGTH(iommu_destroy, IOMMU_DESTROY);
+	TEST_LENGTH(iommu_hw_info, IOMMU_GET_HW_INFO);
 	TEST_LENGTH(iommu_ioas_alloc, IOMMU_IOAS_ALLOC);
 	TEST_LENGTH(iommu_ioas_iova_ranges, IOMMU_IOAS_IOVA_RANGES);
 	TEST_LENGTH(iommu_ioas_allow_iovas, IOMMU_IOAS_ALLOW_IOVAS);
@@ -185,6 +186,7 @@  FIXTURE(iommufd_ioas)
 	uint32_t ioas_id;
 	uint32_t stdev_id;
 	uint32_t hwpt_id;
+	uint32_t device_id;
 	uint64_t base_iova;
 };
 
@@ -211,7 +213,7 @@  FIXTURE_SETUP(iommufd_ioas)
 
 	for (i = 0; i != variant->mock_domains; i++) {
 		test_cmd_mock_domain(self->ioas_id, &self->stdev_id,
-				     &self->hwpt_id, NULL);
+				     &self->hwpt_id, &self->device_id);
 		self->base_iova = MOCK_APERTURE_START;
 	}
 }
@@ -290,6 +292,32 @@  TEST_F(iommufd_ioas, ioas_area_auto_destroy)
 	}
 }
 
+TEST_F(iommufd_ioas, get_hw_info)
+{
+	struct iommu_test_hw_info buffer_exact;
+	struct iommu_test_hw_info_buffer {
+		struct iommu_test_hw_info info;
+		uint64_t trailing_bytes;
+	} buffer_larger;
+
+	if (self->device_id) {
+		/* Provide a zero-size user_buffer */
+		test_cmd_get_hw_info(self->device_id, NULL, 0);
+		/* Provide a user_buffer with exact size */
+		test_cmd_get_hw_info(self->device_id, &buffer_exact, sizeof(buffer_exact));
+		/*
+		 * Provide a user_buffer with size larger than the exact size to check if
+		 * kernel zero the trailing bytes.
+		 */
+		test_cmd_get_hw_info(self->device_id, &buffer_larger, sizeof(buffer_larger));
+	} else {
+		test_err_get_hw_info(ENOENT, self->device_id,
+				     &buffer_exact, sizeof(buffer_exact));
+		test_err_get_hw_info(ENOENT, self->device_id,
+				     &buffer_larger, sizeof(buffer_larger));
+	}
+}
+
 TEST_F(iommufd_ioas, area)
 {
 	int i;
diff --git a/tools/testing/selftests/iommu/iommufd_fail_nth.c b/tools/testing/selftests/iommu/iommufd_fail_nth.c
index d4c552e56948..a220ca2a689d 100644
--- a/tools/testing/selftests/iommu/iommufd_fail_nth.c
+++ b/tools/testing/selftests/iommu/iommufd_fail_nth.c
@@ -576,6 +576,7 @@  TEST_FAIL_NTH(basic_fail_nth, access_pin_domain)
 /* device.c */
 TEST_FAIL_NTH(basic_fail_nth, device)
 {
+	struct iommu_test_hw_info info;
 	uint32_t ioas_id;
 	uint32_t ioas_id2;
 	uint32_t stdev_id;
@@ -611,6 +612,9 @@  TEST_FAIL_NTH(basic_fail_nth, device)
 				  &idev_id))
 		return -1;
 
+	if (_test_cmd_get_hw_info(self->fd, idev_id, &info, sizeof(info)))
+		return -1;
+
 	if (_test_cmd_hwpt_alloc(self->fd, idev_id, ioas_id, &hwpt_id))
 		return -1;
 
diff --git a/tools/testing/selftests/iommu/iommufd_utils.h b/tools/testing/selftests/iommu/iommufd_utils.h
index 70353e68e599..097418f2fdb3 100644
--- a/tools/testing/selftests/iommu/iommufd_utils.h
+++ b/tools/testing/selftests/iommu/iommufd_utils.h
@@ -348,3 +348,59 @@  static void teardown_iommufd(int fd, struct __test_metadata *_metadata)
 	})
 
 #endif
+
+/* @data can be NULL */
+static int _test_cmd_get_hw_info(int fd, __u32 device_id,
+				 void *data, size_t data_len)
+{
+	struct iommu_hw_info cmd = {
+		.size = sizeof(cmd),
+		.dev_id = device_id,
+		.data_len = data_len,
+		.data_uptr = (uint64_t)data,
+	};
+	struct iommu_test_hw_info *info = (struct iommu_test_hw_info *)data;
+	int ret;
+
+	ret = ioctl(fd, IOMMU_GET_HW_INFO, &cmd);
+	if (ret)
+		return ret;
+
+	assert(cmd.out_data_type == IOMMU_HW_INFO_TYPE_SELFTEST);
+
+	/*
+	 * The struct iommu_test_hw_info should be the one defined
+	 * by the current kernel.
+	 */
+	assert(cmd.data_len == sizeof(struct iommu_test_hw_info));
+
+	/*
+	 * Trailing bytes should be 0 if user buffer is larger than
+	 * the data that kernel reports.
+	 */
+	if (data_len > cmd.data_len) {
+		char *ptr = (char *)(data + cmd.data_len);
+		int idx = 0;
+
+		while (idx < data_len - cmd.data_len) {
+			assert(!*(ptr + idx));
+			idx++;
+		}
+	}
+
+	if (info) {
+		assert(info->test_reg == IOMMU_HW_INFO_SELFTEST_REGVAL);
+		assert(!info->flags);
+	}
+
+	return 0;
+}
+
+#define test_cmd_get_hw_info(device_id, data, data_len)         \
+	ASSERT_EQ(0, _test_cmd_get_hw_info(self->fd, device_id, \
+					   data, data_len))
+
+#define test_err_get_hw_info(_errno, device_id, data, data_len) \
+	EXPECT_ERRNO(_errno,                                    \
+		     _test_cmd_get_hw_info(self->fd, device_id, \
+					   data, data_len))