Re: [PATCH 9/9] tools/testing/cxl: Test dax_hmem takeover of CXL regions

[Dave Jiang <dave.jiang@intel.com>]

On 3/26/26 10:28 PM, Dan Williams wrote:
> When platform firmware is committed to publishing EFI_CONVENTIONAL_MEMORY
> in the memory map, but CXL fails to assemble the region, dax_hmem can
> attempt to attach a dax device to the memory range.
> 
> Take advantage of the new ability to support multiple "hmem_platform"
> devices, and to enable regression testing of several scenarios:
> 
> * CXL correctly assembles a region, check dax_hmem fails to attach dax
> * CXL fails to assemble a region, check dax_hmem successfully attaches dax
> * Check that loading the dax_cxl driver loads the dax_hmem driver
> * Attempt to race cxl_mock_mem async probe vs dax_hmem probe flushing.
>   Check that both positive and negative cases.
> 
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Reviewed-by: Dave Jiang <dave.jiang@intel.com>


> ---
>  tools/testing/cxl/test/mock.h      |  8 +++++
>  tools/testing/cxl/test/cxl.c       | 57 ++++++++++++++++++++++++++++++
>  tools/testing/cxl/test/hmem_test.c | 47 ++++++++++++++++++++++++
>  tools/testing/cxl/test/mem.c       |  3 ++
>  tools/testing/cxl/test/mock.c      | 50 ++++++++++++++++++++++++++
>  tools/testing/cxl/Kbuild           |  7 ++++
>  tools/testing/cxl/test/Kbuild      |  1 +
>  7 files changed, 173 insertions(+)
>  create mode 100644 tools/testing/cxl/test/hmem_test.c
> 
> diff --git a/tools/testing/cxl/test/mock.h b/tools/testing/cxl/test/mock.h
> index 2684b89c8aa2..4f57dc80ae7d 100644
> --- a/tools/testing/cxl/test/mock.h
> +++ b/tools/testing/cxl/test/mock.h
> @@ -2,6 +2,7 @@
>  
>  #include <linux/list.h>
>  #include <linux/acpi.h>
> +#include <linux/dax.h>
>  #include <cxl.h>
>  
>  struct cxl_mock_ops {
> @@ -27,8 +28,15 @@ struct cxl_mock_ops {
>  	int (*hmat_get_extended_linear_cache_size)(struct resource *backing_res,
>  						   int nid,
>  						   resource_size_t *cache_size);
> +	int (*walk_hmem_resources)(struct device *host, walk_hmem_fn fn);
> +	int (*region_intersects)(resource_size_t start, size_t size,
> +				 unsigned long flags, unsigned long desc);
> +	int (*region_intersects_soft_reserve)(resource_size_t start,
> +					      size_t size);
>  };
>  
> +int hmem_test_init(void);
> +void hmem_test_exit(void);
>  void register_cxl_mock_ops(struct cxl_mock_ops *ops);
>  void unregister_cxl_mock_ops(struct cxl_mock_ops *ops);
>  struct cxl_mock_ops *get_cxl_mock_ops(int *index);
> diff --git a/tools/testing/cxl/test/cxl.c b/tools/testing/cxl/test/cxl.c
> index 7deeb7ff7bdf..9a9f52090c1d 100644
> --- a/tools/testing/cxl/test/cxl.c
> +++ b/tools/testing/cxl/test/cxl.c
> @@ -1121,6 +1121,53 @@ static void mock_cxl_endpoint_parse_cdat(struct cxl_port *port)
>  	cxl_endpoint_get_perf_coordinates(port, ep_c);
>  }
>  
> +/*
> + * Simulate that the first half of mock CXL Window 0 is "Soft Reserve" capacity
> + */
> +static int mock_walk_hmem_resources(struct device *host, walk_hmem_fn fn)
> +{
> +	struct acpi_cedt_cfmws *cfmws = mock_cfmws[0];
> +	struct resource window =
> +		DEFINE_RES_MEM(cfmws->base_hpa, cfmws->window_size / 2);
> +
> +	dev_dbg(host, "walk cxl_test resource: %pr\n", &window);
> +	return fn(host, 0, &window);
> +}
> +
> +/*
> + * This should only be called by the dax_hmem case, treat mismatches (negative
> + * result) as "fallback to base region_intersects()". Simulate that the first
> + * half of mock CXL Window 0 is IORES_DESC_CXL capacity.
> + */
> +static int mock_region_intersects(resource_size_t start, size_t size,
> +				  unsigned long flags, unsigned long desc)
> +{
> +	struct resource res = DEFINE_RES_MEM(start, size);
> +	struct acpi_cedt_cfmws *cfmws = mock_cfmws[0];
> +	struct resource window =
> +		DEFINE_RES_MEM(cfmws->base_hpa, cfmws->window_size / 2);
> +
> +	if (resource_overlaps(&res, &window))
> +		return REGION_INTERSECTS;
> +	pr_debug("warning: no cxl_test CXL intersection for %pr\n", &res);
> +	return -1;
> +}
> +
> +
> +static int
> +mock_region_intersects_soft_reserve(resource_size_t start, size_t size)
> +{
> +	struct resource res = DEFINE_RES_MEM(start, size);
> +	struct acpi_cedt_cfmws *cfmws = mock_cfmws[0];
> +	struct resource window =
> +		DEFINE_RES_MEM(cfmws->base_hpa, cfmws->window_size / 2);
> +
> +	if (resource_overlaps(&res, &window))
> +		return REGION_INTERSECTS;
> +	pr_debug("warning: no cxl_test soft reserve intersection for %pr\n", &res);
> +	return -1;
> +}
> +
>  static struct cxl_mock_ops cxl_mock_ops = {
>  	.is_mock_adev = is_mock_adev,
>  	.is_mock_bridge = is_mock_bridge,
> @@ -1136,6 +1183,9 @@ static struct cxl_mock_ops cxl_mock_ops = {
>  	.devm_cxl_add_dport_by_dev = mock_cxl_add_dport_by_dev,
>  	.hmat_get_extended_linear_cache_size =
>  		mock_hmat_get_extended_linear_cache_size,
> +	.walk_hmem_resources = mock_walk_hmem_resources,
> +	.region_intersects = mock_region_intersects,
> +	.region_intersects_soft_reserve = mock_region_intersects_soft_reserve,
>  	.list = LIST_HEAD_INIT(cxl_mock_ops.list),
>  };
>  
> @@ -1561,8 +1611,14 @@ static __init int cxl_test_init(void)
>  	if (rc)
>  		goto err_root;
>  
> +	rc = hmem_test_init();
> +	if (rc)
> +		goto err_mem;
> +
>  	return 0;
>  
> +err_mem:
> +	cxl_mem_exit();
>  err_root:
>  	platform_device_put(cxl_acpi);
>  err_rch:
> @@ -1600,6 +1656,7 @@ static __exit void cxl_test_exit(void)
>  {
>  	int i;
>  
> +	hmem_test_exit();
>  	cxl_mem_exit();
>  	platform_device_unregister(cxl_acpi);
>  	cxl_rch_topo_exit();
> diff --git a/tools/testing/cxl/test/hmem_test.c b/tools/testing/cxl/test/hmem_test.c
> new file mode 100644
> index 000000000000..3a1a089e1721
> --- /dev/null
> +++ b/tools/testing/cxl/test/hmem_test.c
> @@ -0,0 +1,47 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (C) 2026 Intel Corporation */
> +#include <linux/moduleparam.h>
> +#include <linux/workqueue.h>
> +#include "../../../drivers/dax/bus.h"
> +
> +static bool hmem_test;
> +
> +static void hmem_test_work(struct work_struct *work)
> +{
> +}
> +
> +static void hmem_test_release(struct device *dev)
> +{
> +	struct hmem_platform_device *hpdev =
> +		container_of(dev, typeof(*hpdev), pdev.dev);
> +
> +	memset(hpdev, 0, sizeof(*hpdev));
> +}
> +
> +static struct hmem_platform_device hmem_test_device = {
> +	.pdev = {
> +		.name = "hmem_platform",
> +		.id = 1,
> +		.dev = {
> +			.release = hmem_test_release,
> +		},
> +	},
> +	.work = __WORK_INITIALIZER(hmem_test_device.work, hmem_test_work),
> +};
> +
> +int hmem_test_init(void)
> +{
> +	if (!hmem_test)
> +		return 0;
> +
> +	return platform_device_register(&hmem_test_device.pdev);
> +}
> +
> +void hmem_test_exit(void)
> +{
> +	if (hmem_test)
> +		platform_device_unregister(&hmem_test_device.pdev);
> +}
> +
> +module_param(hmem_test, bool, 0444);
> +MODULE_PARM_DESC(hmem_test, "Enable/disable the dax_hmem test platform device");
> diff --git a/tools/testing/cxl/test/mem.c b/tools/testing/cxl/test/mem.c
> index cb87e8c0e63c..cc847e9aeceb 100644
> --- a/tools/testing/cxl/test/mem.c
> +++ b/tools/testing/cxl/test/mem.c
> @@ -1695,6 +1695,9 @@ static int cxl_mock_mem_probe(struct platform_device *pdev)
>  	struct cxl_dpa_info range_info = { 0 };
>  	int rc;
>  
> +	/* Increase async probe race window */
> +	usleep_range(500*1000, 1000*1000);
> +
>  	mdata = devm_kzalloc(dev, sizeof(*mdata), GFP_KERNEL);
>  	if (!mdata)
>  		return -ENOMEM;
> diff --git a/tools/testing/cxl/test/mock.c b/tools/testing/cxl/test/mock.c
> index b8fcb50c1027..6454b868b122 100644
> --- a/tools/testing/cxl/test/mock.c
> +++ b/tools/testing/cxl/test/mock.c
> @@ -251,6 +251,56 @@ struct cxl_dport *__wrap_devm_cxl_add_dport_by_dev(struct cxl_port *port,
>  }
>  EXPORT_SYMBOL_NS_GPL(__wrap_devm_cxl_add_dport_by_dev, "CXL");
>  
> +int __wrap_region_intersects(resource_size_t start, size_t size,
> +			     unsigned long flags, unsigned long desc)
> +{
> +	int rc = -1;
> +	int index;
> +	struct cxl_mock_ops *ops = get_cxl_mock_ops(&index);
> +
> +	if (ops)
> +		rc = ops->region_intersects(start, size, flags, desc);
> +	if (rc < 0)
> +		rc = region_intersects(start, size, flags, desc);
> +	put_cxl_mock_ops(index);
> +
> +	return rc;
> +}
> +EXPORT_SYMBOL_GPL(__wrap_region_intersects);
> +
> +int __wrap_region_intersects_soft_reserve(resource_size_t start, size_t size)
> +{
> +	int rc = -1;
> +	int index;
> +	struct cxl_mock_ops *ops = get_cxl_mock_ops(&index);
> +
> +	if (ops)
> +		rc = ops->region_intersects_soft_reserve(start, size);
> +	if (rc < 0)
> +		rc = region_intersects_soft_reserve(start, size);
> +	put_cxl_mock_ops(index);
> +
> +	return rc;
> +}
> +EXPORT_SYMBOL_GPL(__wrap_region_intersects_soft_reserve);
> +
> +int __wrap_walk_hmem_resources(struct device *host, walk_hmem_fn fn)
> +{
> +	int index, rc = 0;
> +	bool is_mock = strcmp(dev_name(host), "hmem_platform.1") == 0;
> +	struct cxl_mock_ops *ops = get_cxl_mock_ops(&index);
> +
> +	if (is_mock) {
> +		if (ops)
> +			rc = ops->walk_hmem_resources(host, fn);
> +	} else {
> +		rc = walk_hmem_resources(host, fn);
> +	}
> +	put_cxl_mock_ops(index);
> +	return rc;
> +}
> +EXPORT_SYMBOL_GPL(__wrap_walk_hmem_resources);
> +
>  MODULE_LICENSE("GPL v2");
>  MODULE_DESCRIPTION("cxl_test: emulation module");
>  MODULE_IMPORT_NS("ACPI");
> diff --git a/tools/testing/cxl/Kbuild b/tools/testing/cxl/Kbuild
> index 53d84a6874b7..540425c7cd41 100644
> --- a/tools/testing/cxl/Kbuild
> +++ b/tools/testing/cxl/Kbuild
> @@ -11,8 +11,12 @@ ldflags-y += --wrap=devm_cxl_endpoint_decoders_setup
>  ldflags-y += --wrap=hmat_get_extended_linear_cache_size
>  ldflags-y += --wrap=devm_cxl_add_dport_by_dev
>  ldflags-y += --wrap=devm_cxl_switch_port_decoders_setup
> +ldflags-y += --wrap=walk_hmem_resources
> +ldflags-y += --wrap=region_intersects
> +ldflags-y += --wrap=region_intersects_soft_reserve
>  
>  DRIVERS := ../../../drivers
> +DAX_HMEM_SRC := $(DRIVERS)/dax/hmem
>  CXL_SRC := $(DRIVERS)/cxl
>  CXL_CORE_SRC := $(DRIVERS)/cxl/core
>  ccflags-y := -I$(srctree)/drivers/cxl/
> @@ -70,6 +74,9 @@ cxl_core-y += config_check.o
>  cxl_core-y += cxl_core_test.o
>  cxl_core-y += cxl_core_exports.o
>  
> +obj-m += dax_hmem.o
> +dax_hmem-y := $(DAX_HMEM_SRC)/hmem.o
> +
>  KBUILD_CFLAGS := $(filter-out -Wmissing-prototypes -Wmissing-declarations, $(KBUILD_CFLAGS))
>  
>  obj-m += test/
> diff --git a/tools/testing/cxl/test/Kbuild b/tools/testing/cxl/test/Kbuild
> index af50972c8b6d..c168e3c998a7 100644
> --- a/tools/testing/cxl/test/Kbuild
> +++ b/tools/testing/cxl/test/Kbuild
> @@ -7,6 +7,7 @@ obj-m += cxl_mock_mem.o
>  obj-m += cxl_translate.o
>  
>  cxl_test-y := cxl.o
> +cxl_test-y += hmem_test.o
>  cxl_mock-y := mock.o
>  cxl_mock_mem-y := mem.o
>