Re: [PATCH v5 2/3] cxl/core/region: move dax region device logic into region_dax.c

[Anisa Su]

On Thu, Mar 26, 2026 at 10:02:02PM -0400, Gregory Price wrote:
> core/region.c is overloaded with per-region control logic (pmem, dax,
> sysram, etc). Move the CXL DAX region device infrastructure from
> region.c into a new region_dax.c file.
> 
> This will also allow us to add additional dax-driver integration paths
> that don't further dirty the core region.c logic.
> 
> No functional changes.
> 
> Signed-off-by: Gregory Price <gourry@xxxxxxxxxx>
> Co-developed-by: Ira Weiny <ira.weiny@xxxxxxxxx>
> Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx>
> ---
>  drivers/cxl/core/Makefile     |   2 +-
>  drivers/cxl/core/core.h       |   1 +
>  drivers/cxl/core/region.c     |  99 ------------------------------
>  drivers/cxl/core/region_dax.c | 109 ++++++++++++++++++++++++++++++++++
>  tools/testing/cxl/Kbuild      |   2 +-
>  5 files changed, 112 insertions(+), 101 deletions(-)
>  create mode 100644 drivers/cxl/core/region_dax.c
> 
> diff --git a/drivers/cxl/core/Makefile b/drivers/cxl/core/Makefile
> index f73776fe323b..ce7213818d3c 100644
> --- a/drivers/cxl/core/Makefile
> +++ b/drivers/cxl/core/Makefile
> @@ -15,7 +15,7 @@ cxl_core-y += hdm.o
>  cxl_core-y += pmu.o
>  cxl_core-y += cdat.o
>  cxl_core-$(CONFIG_TRACING) += trace.o
> -cxl_core-$(CONFIG_CXL_REGION) += region.o region_pmem.o
> +cxl_core-$(CONFIG_CXL_REGION) += region.o region_pmem.o region_dax.o
>  cxl_core-$(CONFIG_CXL_MCE) += mce.o
>  cxl_core-$(CONFIG_CXL_FEATURES) += features.o
>  cxl_core-$(CONFIG_CXL_EDAC_MEM_FEATURES) += edac.o
> diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h
> index ef03966eeabd..82ca3a476708 100644
> --- a/drivers/cxl/core/core.h
> +++ b/drivers/cxl/core/core.h
> @@ -50,6 +50,7 @@ int cxl_get_poison_by_endpoint(struct cxl_port *port);
>  struct cxl_region *cxl_dpa_to_region(const struct cxl_memdev *cxlmd, u64 dpa);
>  u64 cxl_dpa_to_hpa(struct cxl_region *cxlr, const struct cxl_memdev *cxlmd,
>  		   u64 dpa);
> +int devm_cxl_add_dax_region(struct cxl_region *cxlr);
>  int devm_cxl_add_pmem_region(struct cxl_region *cxlr);
>  
>  #else
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 72aee1408efb..6a2ef3475764 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -3436,105 +3436,6 @@ static int region_offset_to_dpa_result(struct cxl_region *cxlr, u64 offset,
>  	return -ENXIO;
>  }
>  
> -static void cxl_dax_region_release(struct device *dev)
> -{
> -	struct cxl_dax_region *cxlr_dax = to_cxl_dax_region(dev);
> -
> -	kfree(cxlr_dax);
> -}
> -
> -static const struct attribute_group *cxl_dax_region_attribute_groups[] = {
> -	&cxl_base_attribute_group,
> -	NULL,
> -};
> -
> -const struct device_type cxl_dax_region_type = {
> -	.name = "cxl_dax_region",
> -	.release = cxl_dax_region_release,
> -	.groups = cxl_dax_region_attribute_groups,
> -};
> -
> -static bool is_cxl_dax_region(struct device *dev)
> -{
> -	return dev->type == &cxl_dax_region_type;
> -}
> -
> -struct cxl_dax_region *to_cxl_dax_region(struct device *dev)
> -{
> -	if (dev_WARN_ONCE(dev, !is_cxl_dax_region(dev),
> -			  "not a cxl_dax_region device\n"))
> -		return NULL;
> -	return container_of(dev, struct cxl_dax_region, dev);
> -}
> -EXPORT_SYMBOL_NS_GPL(to_cxl_dax_region, "CXL");
> -
> -static struct lock_class_key cxl_dax_region_key;
> -
> -static struct cxl_dax_region *cxl_dax_region_alloc(struct cxl_region *cxlr)
> -{
> -	struct cxl_region_params *p = &cxlr->params;
> -	struct cxl_dax_region *cxlr_dax;
> -	struct device *dev;
> -
> -	guard(rwsem_read)(&cxl_rwsem.region);
> -	if (p->state != CXL_CONFIG_COMMIT)
> -		return ERR_PTR(-ENXIO);
> -
> -	cxlr_dax = kzalloc_obj(*cxlr_dax);
> -	if (!cxlr_dax)
> -		return ERR_PTR(-ENOMEM);
> -
> -	cxlr_dax->hpa_range.start = p->res->start;
> -	cxlr_dax->hpa_range.end = p->res->end;
> -
> -	dev = &cxlr_dax->dev;
> -	cxlr_dax->cxlr = cxlr;
> -	device_initialize(dev);
> -	lockdep_set_class(&dev->mutex, &cxl_dax_region_key);
> -	device_set_pm_not_required(dev);
> -	dev->parent = &cxlr->dev;
> -	dev->bus = &cxl_bus_type;
> -	dev->type = &cxl_dax_region_type;
> -
> -	return cxlr_dax;
> -}
> -
> -static void cxlr_dax_unregister(void *_cxlr_dax)
> -{
> -	struct cxl_dax_region *cxlr_dax = _cxlr_dax;
> -
> -	device_unregister(&cxlr_dax->dev);
> -}
> -
> -static int devm_cxl_add_dax_region(struct cxl_region *cxlr)
> -{
> -	struct cxl_dax_region *cxlr_dax;
> -	struct device *dev;
> -	int rc;
> -
> -	cxlr_dax = cxl_dax_region_alloc(cxlr);
> -	if (IS_ERR(cxlr_dax))
> -		return PTR_ERR(cxlr_dax);
> -
> -	dev = &cxlr_dax->dev;
> -	rc = dev_set_name(dev, "dax_region%d", cxlr->id);
> -	if (rc)
> -		goto err;
> -
> -	rc = device_add(dev);
> -	if (rc)
> -		goto err;
> -
> -	dev_dbg(&cxlr->dev, "%s: register %s\n", dev_name(dev->parent),
> -		dev_name(dev));
> -
> -	return devm_add_action_or_reset(&cxlr->dev, cxlr_dax_unregister,
> -					cxlr_dax);
> -err:
> -	put_device(dev);
> -	return rc;
> -}
> -
>  static int match_root_decoder(struct device *dev, const void *data)
>  {
>  	const struct range *r1, *r2 = data;
> diff --git a/drivers/cxl/core/region_dax.c b/drivers/cxl/core/region_dax.c
> new file mode 100644
> index 000000000000..fe367759ac69
> --- /dev/null
> +++ b/drivers/cxl/core/region_dax.c
> @@ -0,0 +1,109 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright(c) 2022 Intel Corporation. All rights reserved.
> + * Copyright(c) 2026 Meta Technologies Inc. All rights reserved.
> + */
> +#include <linux/device.h>
> +#include <linux/slab.h>
> +#include <cxlmem.h>
> +#include <cxl.h>
> +#include "core.h"
> +
> +static void cxl_dax_region_release(struct device *dev)
> +{
> +	struct cxl_dax_region *cxlr_dax = to_cxl_dax_region(dev);
> +
> +	kfree(cxlr_dax);
> +}
> +
> +static const struct attribute_group *cxl_dax_region_attribute_groups[] = {
> +	&cxl_base_attribute_group,
> +	NULL
> +};
> +
> +const struct device_type cxl_dax_region_type = {
> +	.name = "cxl_dax_region",
> +	.release = cxl_dax_region_release,
> +	.groups = cxl_dax_region_attribute_groups,
> +};
> +
> +static bool is_cxl_dax_region(struct device *dev)
> +{
> +	return dev->type == &cxl_dax_region_type;
> +}
> +
> +struct cxl_dax_region *to_cxl_dax_region(struct device *dev)
> +{
> +	if (dev_WARN_ONCE(dev, !is_cxl_dax_region(dev),
> +			  "not a cxl_dax_region device\n"))
> +		return NULL;
> +	return container_of(dev, struct cxl_dax_region, dev);
> +}
> +EXPORT_SYMBOL_NS_GPL(to_cxl_dax_region, "CXL");
> +
> +static struct lock_class_key cxl_dax_region_key;
> +
> +static struct cxl_dax_region *cxl_dax_region_alloc(struct cxl_region *cxlr)
> +{
> +	struct cxl_region_params *p = &cxlr->params;
> +	struct cxl_dax_region *cxlr_dax;
> +	struct device *dev;
> +
> +	guard(rwsem_read)(&cxl_rwsem.region);
> +	if (p->state != CXL_CONFIG_COMMIT)
> +		return ERR_PTR(-ENXIO);
> +
> +	cxlr_dax = kzalloc_obj(*cxlr_dax);
> +	if (!cxlr_dax)
> +		return ERR_PTR(-ENOMEM);
> +
> +	cxlr_dax->hpa_range.start = p->res->start;
> +	cxlr_dax->hpa_range.end = p->res->end;
> +
> +	dev = &cxlr_dax->dev;
> +	cxlr_dax->cxlr = cxlr;
	cxlr->cxlr_dax = cxlr_dax;

Running into segfaults without this ^
> +	device_initialize(dev);
> +	lockdep_set_class(&dev->mutex, &cxl_dax_region_key);
> +	device_set_pm_not_required(dev);
> +	dev->parent = &cxlr->dev;
> +	dev->bus = &cxl_bus_type;
> +	dev->type = &cxl_dax_region_type;
> +
> +	return cxlr_dax;
> +}
> +
> +static void cxlr_dax_unregister(void *_cxlr_dax)
> +{
> +	struct cxl_dax_region *cxlr_dax = _cxlr_dax;
> +
> +	device_unregister(&cxlr_dax->dev);
> +}
> +
> +int devm_cxl_add_dax_region(struct cxl_region *cxlr)
> +{
> +	struct cxl_dax_region *cxlr_dax;
> +	struct device *dev;
> +	int rc;
> +
> +	cxlr_dax = cxl_dax_region_alloc(cxlr);
> +	if (IS_ERR(cxlr_dax))
> +		return PTR_ERR(cxlr_dax);
> +
> +	dev = &cxlr_dax->dev;
> +	rc = dev_set_name(dev, "dax_region%d", cxlr->id);
> +	if (rc)
> +		goto err;
> +
> +	rc = device_add(dev);
> +	if (rc)
> +		goto err;
> +
> +	dev_dbg(&cxlr->dev, "%s: register %s\n", dev_name(dev->parent),
> +		dev_name(dev));
> +
> +	return devm_add_action_or_reset(&cxlr->dev, cxlr_dax_unregister,
> +					cxlr_dax);
> +err:
> +	put_device(dev);
> +	return rc;
> +}
> diff --git a/tools/testing/cxl/Kbuild b/tools/testing/cxl/Kbuild
> index f53d79a05661..d2b291e5f842 100644
> --- a/tools/testing/cxl/Kbuild
> +++ b/tools/testing/cxl/Kbuild
> @@ -59,7 +59,7 @@ cxl_core-y += $(CXL_CORE_SRC)/hdm.o
>  cxl_core-y += $(CXL_CORE_SRC)/pmu.o
>  cxl_core-y += $(CXL_CORE_SRC)/cdat.o
>  cxl_core-$(CONFIG_TRACING) += $(CXL_CORE_SRC)/trace.o
> -cxl_core-$(CONFIG_CXL_REGION) += $(CXL_CORE_SRC)/region.o $(CXL_CORE_SRC)/region_pmem.o
> +cxl_core-$(CONFIG_CXL_REGION) += $(CXL_CORE_SRC)/region.o $(CXL_CORE_SRC)/region_pmem.o $(CXL_CORE_SRC)/region_dax.o
>  cxl_core-$(CONFIG_CXL_MCE) += $(CXL_CORE_SRC)/mce.o
>  cxl_core-$(CONFIG_CXL_FEATURES) += $(CXL_CORE_SRC)/features.o
>  cxl_core-$(CONFIG_CXL_EDAC_MEM_FEATURES) += $(CXL_CORE_SRC)/edac.o
> -- 
> 2.53.0
>