tools/testing/cxl: Introduce a mocked-up CXL port hierarchy

Create an environment for CXL plumbing unit tests. Especially when it
comes to an algorithm for HDM Decoder (Host-managed Device Memory
Decoder) programming, the availability of an in-kernel-tree emulation
environment for CXL configuration complexity and corner cases speeds
development and deters regressions.

The approach taken mirrors what was done for tools/testing/nvdimm/. I.e.
an external module, cxl_test.ko built out of the tools/testing/cxl/
directory, provides mock implementations of kernel APIs and kernel
objects to simulate a real world device hierarchy.

One feedback for the tools/testing/nvdimm/ proposal was "why not do this
in QEMU?". In fact, the CXL development community has developed a QEMU
model for CXL [1]. However, there are a few blocking issues that keep
QEMU from being a tight fit for topology + provisioning unit tests:

1/ The QEMU community has yet to show interest in merging any of this
   support that has had patches on the list since November 2020. So,
   testing CXL to date involves building custom QEMU with out-of-tree
   patches.

2/ CXL mechanisms like cross-host-bridge interleave do not have a clear
   path to be emulated by QEMU without major infrastructure work. This
   is easier to achieve with the alloc_mock_res() approach taken in this
   patch to shortcut-define emulated system physical address ranges with
   interleave behavior.

The QEMU enabling has been critical to get the driver off the ground,
and may still move forward, but it does not address the ongoing needs of
a regression testing environment and test driven development.

This patch adds an ACPI CXL Platform definition with emulated CXL
multi-ported host-bridges. A follow on patch adds emulated memory
expander devices.

Acked-by: Ben Widawsky <ben.widawsky@intel.com>
Reported-by: Vishal Verma <vishal.l.verma@intel.com>
Link: https://lore.kernel.org/r/20210202005948.241655-1-ben.widawsky@intel.com [1]
Link: https://lore.kernel.org/r/163164680798.2831381.838684634806668012.stgit@dwillia2-desk3.amr.corp.intel.com
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 509 insertions, 0 deletions

diff --git a/tools/testing/cxl/test/cxl.c b/tools/testing/cxl/test/cxl.c
new file mode 100644
index 000000000000..1c47b34244a4
--- /dev/null
+++ b/tools/testing/cxl/test/cxl.c
@@ -0,0 +1,509 @@
+// SPDX-License-Identifier: GPL-2.0-only
+// Copyright(c) 2021 Intel Corporation. All rights reserved.
+
+#include <linux/platform_device.h>
+#include <linux/genalloc.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/acpi.h>
+#include <linux/pci.h>
+#include <linux/mm.h>
+#include "mock.h"
+
+#define NR_CXL_HOST_BRIDGES 4
+#define NR_CXL_ROOT_PORTS 2
+
+static struct platform_device *cxl_acpi;
+static struct platform_device *cxl_host_bridge[NR_CXL_HOST_BRIDGES];
+static struct platform_device
+	*cxl_root_port[NR_CXL_HOST_BRIDGES * NR_CXL_ROOT_PORTS];
+
+static struct acpi_device acpi0017_mock;
+static struct acpi_device host_bridge[NR_CXL_HOST_BRIDGES] = {
+	[0] = {
+		.handle = &host_bridge[0],
+	},
+	[1] = {
+		.handle = &host_bridge[1],
+	},
+	[2] = {
+		.handle = &host_bridge[2],
+	},
+	[3] = {
+		.handle = &host_bridge[3],
+	},
+};
+
+static bool is_mock_dev(struct device *dev)
+{
+	if (dev == &cxl_acpi->dev)
+		return true;
+	return false;
+}
+
+static bool is_mock_adev(struct acpi_device *adev)
+{
+	int i;
+
+	if (adev == &acpi0017_mock)
+		return true;
+
+	for (i = 0; i < ARRAY_SIZE(host_bridge); i++)
+		if (adev == &host_bridge[i])
+			return true;
+
+	return false;
+}
+
+static struct {
+	struct acpi_table_cedt cedt;
+	struct acpi_cedt_chbs chbs[NR_CXL_HOST_BRIDGES];
+	struct {
+		struct acpi_cedt_cfmws cfmws;
+		u32 target[1];
+	} cfmws0;
+	struct {
+		struct acpi_cedt_cfmws cfmws;
+		u32 target[4];
+	} cfmws1;
+	struct {
+		struct acpi_cedt_cfmws cfmws;
+		u32 target[1];
+	} cfmws2;
+	struct {
+		struct acpi_cedt_cfmws cfmws;
+		u32 target[4];
+	} cfmws3;
+} __packed mock_cedt = {
+	.cedt = {
+		.header = {
+			.signature = "CEDT",
+			.length = sizeof(mock_cedt),
+			.revision = 1,
+		},
+	},
+	.chbs[0] = {
+		.header = {
+			.type = ACPI_CEDT_TYPE_CHBS,
+			.length = sizeof(mock_cedt.chbs[0]),
+		},
+		.uid = 0,
+		.cxl_version = ACPI_CEDT_CHBS_VERSION_CXL20,
+	},
+	.chbs[1] = {
+		.header = {
+			.type = ACPI_CEDT_TYPE_CHBS,
+			.length = sizeof(mock_cedt.chbs[0]),
+		},
+		.uid = 1,
+		.cxl_version = ACPI_CEDT_CHBS_VERSION_CXL20,
+	},
+	.chbs[2] = {
+		.header = {
+			.type = ACPI_CEDT_TYPE_CHBS,
+			.length = sizeof(mock_cedt.chbs[0]),
+		},
+		.uid = 2,
+		.cxl_version = ACPI_CEDT_CHBS_VERSION_CXL20,
+	},
+	.chbs[3] = {
+		.header = {
+			.type = ACPI_CEDT_TYPE_CHBS,
+			.length = sizeof(mock_cedt.chbs[0]),
+		},
+		.uid = 3,
+		.cxl_version = ACPI_CEDT_CHBS_VERSION_CXL20,
+	},
+	.cfmws0 = {
+		.cfmws = {
+			.header = {
+				.type = ACPI_CEDT_TYPE_CFMWS,
+				.length = sizeof(mock_cedt.cfmws0),
+			},
+			.interleave_ways = 0,
+			.granularity = 4,
+			.restrictions = ACPI_CEDT_CFMWS_RESTRICT_TYPE3 |
+					ACPI_CEDT_CFMWS_RESTRICT_VOLATILE,
+			.qtg_id = 0,
+			.window_size = SZ_256M,
+		},
+		.target = { 0 },
+	},
+	.cfmws1 = {
+		.cfmws = {
+			.header = {
+				.type = ACPI_CEDT_TYPE_CFMWS,
+				.length = sizeof(mock_cedt.cfmws1),
+			},
+			.interleave_ways = 2,
+			.granularity = 4,
+			.restrictions = ACPI_CEDT_CFMWS_RESTRICT_TYPE3 |
+					ACPI_CEDT_CFMWS_RESTRICT_VOLATILE,
+			.qtg_id = 1,
+			.window_size = SZ_256M * 4,
+		},
+		.target = { 0, 1, 2, 3 },
+	},
+	.cfmws2 = {
+		.cfmws = {
+			.header = {
+				.type = ACPI_CEDT_TYPE_CFMWS,
+				.length = sizeof(mock_cedt.cfmws2),
+			},
+			.interleave_ways = 0,
+			.granularity = 4,
+			.restrictions = ACPI_CEDT_CFMWS_RESTRICT_TYPE3 |
+					ACPI_CEDT_CFMWS_RESTRICT_PMEM,
+			.qtg_id = 2,
+			.window_size = SZ_256M,
+		},
+		.target = { 0 },
+	},
+	.cfmws3 = {
+		.cfmws = {
+			.header = {
+				.type = ACPI_CEDT_TYPE_CFMWS,
+				.length = sizeof(mock_cedt.cfmws3),
+			},
+			.interleave_ways = 2,
+			.granularity = 4,
+			.restrictions = ACPI_CEDT_CFMWS_RESTRICT_TYPE3 |
+					ACPI_CEDT_CFMWS_RESTRICT_PMEM,
+			.qtg_id = 3,
+			.window_size = SZ_256M * 4,
+		},
+		.target = { 0, 1, 2, 3 },
+	},
+};
+
+struct cxl_mock_res {
+	struct list_head list;
+	struct range range;
+};
+
+static LIST_HEAD(mock_res);
+static DEFINE_MUTEX(mock_res_lock);
+static struct gen_pool *cxl_mock_pool;
+
+static void depopulate_all_mock_resources(void)
+{
+	struct cxl_mock_res *res, *_res;
+
+	mutex_lock(&mock_res_lock);
+	list_for_each_entry_safe(res, _res, &mock_res, list) {
+		gen_pool_free(cxl_mock_pool, res->range.start,
+			      range_len(&res->range));
+		list_del(&res->list);
+		kfree(res);
+	}
+	mutex_unlock(&mock_res_lock);
+}
+
+static struct cxl_mock_res *alloc_mock_res(resource_size_t size)
+{
+	struct cxl_mock_res *res = kzalloc(sizeof(*res), GFP_KERNEL);
+	struct genpool_data_align data = {
+		.align = SZ_256M,
+	};
+	unsigned long phys;
+
+	INIT_LIST_HEAD(&res->list);
+	phys = gen_pool_alloc_algo(cxl_mock_pool, size,
+				   gen_pool_first_fit_align, &data);
+	if (!phys)
+		return NULL;
+
+	res->range = (struct range) {
+		.start = phys,
+		.end = phys + size - 1,
+	};
+	mutex_lock(&mock_res_lock);
+	list_add(&res->list, &mock_res);
+	mutex_unlock(&mock_res_lock);
+
+	return res;
+}
+
+static int populate_cedt(void)
+{
+	struct acpi_cedt_cfmws *cfmws[4] = {
+		[0] = &mock_cedt.cfmws0.cfmws,
+		[1] = &mock_cedt.cfmws1.cfmws,
+		[2] = &mock_cedt.cfmws2.cfmws,
+		[3] = &mock_cedt.cfmws3.cfmws,
+	};
+	struct cxl_mock_res *res;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(mock_cedt.chbs); i++) {
+		struct acpi_cedt_chbs *chbs = &mock_cedt.chbs[i];
+		resource_size_t size;
+
+		if (chbs->cxl_version == ACPI_CEDT_CHBS_VERSION_CXL20)
+			size = ACPI_CEDT_CHBS_LENGTH_CXL20;
+		else
+			size = ACPI_CEDT_CHBS_LENGTH_CXL11;
+
+		res = alloc_mock_res(size);
+		if (!res)
+			return -ENOMEM;
+		chbs->base = res->range.start;
+		chbs->length = size;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(cfmws); i++) {
+		struct acpi_cedt_cfmws *window = cfmws[i];
+
+		res = alloc_mock_res(window->window_size);
+		if (!res)
+			return -ENOMEM;
+		window->base_hpa = res->range.start;
+	}
+
+	return 0;
+}
+
+static acpi_status mock_acpi_get_table(char *signature, u32 instance,
+				       struct acpi_table_header **out_table)
+{
+	if (instance < U32_MAX || strcmp(signature, ACPI_SIG_CEDT) != 0)
+		return acpi_get_table(signature, instance, out_table);
+
+	*out_table = (struct acpi_table_header *) &mock_cedt;
+	return AE_OK;
+}
+
+static void mock_acpi_put_table(struct acpi_table_header *table)
+{
+	if (table == (struct acpi_table_header *) &mock_cedt)
+		return;
+	acpi_put_table(table);
+}
+
+static bool is_mock_bridge(struct device *dev)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(cxl_host_bridge); i++)
+		if (dev == &cxl_host_bridge[i]->dev)
+			return true;
+
+	return false;
+}
+
+static int host_bridge_index(struct acpi_device *adev)
+{
+	return adev - host_bridge;
+}
+
+static struct acpi_device *find_host_bridge(acpi_handle handle)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(host_bridge); i++)
+		if (handle == host_bridge[i].handle)
+			return &host_bridge[i];
+	return NULL;
+}
+
+static acpi_status
+mock_acpi_evaluate_integer(acpi_handle handle, acpi_string pathname,
+			   struct acpi_object_list *arguments,
+			   unsigned long long *data)
+{
+	struct acpi_device *adev = find_host_bridge(handle);
+
+	if (!adev || strcmp(pathname, METHOD_NAME__UID) != 0)
+		return acpi_evaluate_integer(handle, pathname, arguments, data);
+
+	*data = host_bridge_index(adev);
+	return AE_OK;
+}
+
+static struct pci_bus mock_pci_bus[NR_CXL_HOST_BRIDGES];
+static struct acpi_pci_root mock_pci_root[NR_CXL_HOST_BRIDGES] = {
+	[0] = {
+		.bus = &mock_pci_bus[0],
+	},
+	[1] = {
+		.bus = &mock_pci_bus[1],
+	},
+	[2] = {
+		.bus = &mock_pci_bus[2],
+	},
+	[3] = {
+		.bus = &mock_pci_bus[3],
+	},
+};
+
+static struct platform_device *mock_cxl_root_port(struct pci_bus *bus, int index)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(mock_pci_bus); i++)
+		if (bus == &mock_pci_bus[i])
+			return cxl_root_port[index + i * NR_CXL_ROOT_PORTS];
+	return NULL;
+}
+
+static bool is_mock_port(struct platform_device *pdev)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(cxl_root_port); i++)
+		if (pdev == cxl_root_port[i])
+			return true;
+	return false;
+}
+
+static bool is_mock_bus(struct pci_bus *bus)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(mock_pci_bus); i++)
+		if (bus == &mock_pci_bus[i])
+			return true;
+	return false;
+}
+
+static struct acpi_pci_root *mock_acpi_pci_find_root(acpi_handle handle)
+{
+	struct acpi_device *adev = find_host_bridge(handle);
+
+	if (!adev)
+		return acpi_pci_find_root(handle);
+	return &mock_pci_root[host_bridge_index(adev)];
+}
+
+static struct cxl_mock_ops cxl_mock_ops = {
+	.is_mock_adev = is_mock_adev,
+	.is_mock_bridge = is_mock_bridge,
+	.is_mock_bus = is_mock_bus,
+	.is_mock_port = is_mock_port,
+	.is_mock_dev = is_mock_dev,
+	.mock_port = mock_cxl_root_port,
+	.acpi_get_table = mock_acpi_get_table,
+	.acpi_put_table = mock_acpi_put_table,
+	.acpi_evaluate_integer = mock_acpi_evaluate_integer,
+	.acpi_pci_find_root = mock_acpi_pci_find_root,
+	.list = LIST_HEAD_INIT(cxl_mock_ops.list),
+};
+
+static void mock_companion(struct acpi_device *adev, struct device *dev)
+{
+	device_initialize(&adev->dev);
+	fwnode_init(&adev->fwnode, NULL);
+	dev->fwnode = &adev->fwnode;
+	adev->fwnode.dev = dev;
+}
+
+#ifndef SZ_64G
+#define SZ_64G (SZ_32G * 2)
+#endif
+
+#ifndef SZ_512G
+#define SZ_512G (SZ_64G * 8)
+#endif
+
+static __init int cxl_test_init(void)
+{
+	int rc, i;
+
+	register_cxl_mock_ops(&cxl_mock_ops);
+
+	cxl_mock_pool = gen_pool_create(ilog2(SZ_2M), NUMA_NO_NODE);
+	if (!cxl_mock_pool) {
+		rc = -ENOMEM;
+		goto err_gen_pool_create;
+	}
+
+	rc = gen_pool_add(cxl_mock_pool, SZ_512G, SZ_64G, NUMA_NO_NODE);
+	if (rc)
+		goto err_gen_pool_add;
+
+	rc = populate_cedt();
+	if (rc)
+		goto err_populate;
+
+	for (i = 0; i < ARRAY_SIZE(cxl_host_bridge); i++) {
+		struct acpi_device *adev = &host_bridge[i];
+		struct platform_device *pdev;
+
+		pdev = platform_device_alloc("cxl_host_bridge", i);
+		if (!pdev)
+			goto err_bridge;
+
+		mock_companion(adev, &pdev->dev);
+		rc = platform_device_add(pdev);
+		if (rc) {
+			platform_device_put(pdev);
+			goto err_bridge;
+		}
+		cxl_host_bridge[i] = pdev;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(cxl_root_port); i++) {
+		struct platform_device *bridge =
+			cxl_host_bridge[i / NR_CXL_ROOT_PORTS];
+		struct platform_device *pdev;
+
+		pdev = platform_device_alloc("cxl_root_port", i);
+		if (!pdev)
+			goto err_port;
+		pdev->dev.parent = &bridge->dev;
+
+		rc = platform_device_add(pdev);
+		if (rc) {
+			platform_device_put(pdev);
+			goto err_port;
+		}
+		cxl_root_port[i] = pdev;
+	}
+
+	cxl_acpi = platform_device_alloc("cxl_acpi", 0);
+	if (!cxl_acpi)
+		goto err_port;
+
+	mock_companion(&acpi0017_mock, &cxl_acpi->dev);
+	acpi0017_mock.dev.bus = &platform_bus_type;
+
+	rc = platform_device_add(cxl_acpi);
+	if (rc)
+		goto err_add;
+
+	return 0;
+
+err_add:
+	platform_device_put(cxl_acpi);
+err_port:
+	for (i = ARRAY_SIZE(cxl_root_port) - 1; i >= 0; i--)
+		platform_device_unregister(cxl_root_port[i]);
+err_bridge:
+	for (i = ARRAY_SIZE(cxl_host_bridge) - 1; i >= 0; i--)
+		platform_device_unregister(cxl_host_bridge[i]);
+err_populate:
+	depopulate_all_mock_resources();
+err_gen_pool_add:
+	gen_pool_destroy(cxl_mock_pool);
+err_gen_pool_create:
+	unregister_cxl_mock_ops(&cxl_mock_ops);
+	return rc;
+}
+
+static __exit void cxl_test_exit(void)
+{
+	int i;
+
+	platform_device_unregister(cxl_acpi);
+	for (i = ARRAY_SIZE(cxl_root_port) - 1; i >= 0; i--)
+		platform_device_unregister(cxl_root_port[i]);
+	for (i = ARRAY_SIZE(cxl_host_bridge) - 1; i >= 0; i--)
+		platform_device_unregister(cxl_host_bridge[i]);
+	depopulate_all_mock_resources();
+	gen_pool_destroy(cxl_mock_pool);
+	unregister_cxl_mock_ops(&cxl_mock_ops);
+}
+
+module_init(cxl_test_init);
+module_exit(cxl_test_exit);
+MODULE_LICENSE("GPL v2");