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[96.255.20.138]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8c71b859eaesm282041685a.46.2026.01.29.13.04.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 Jan 2026 13:04:57 -0800 (PST) From: Gregory Price To: linux-mm@kvack.org Cc: linux-cxl@vger.kernel.org, nvdimm@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, kernel-team@meta.com, dave@stgolabs.net, jonathan.cameron@huawei.com, dave.jiang@intel.com, alison.schofield@intel.com, vishal.l.verma@intel.com, ira.weiny@intel.com, dan.j.williams@intel.com, willy@infradead.org, jack@suse.cz, terry.bowman@amd.com, john@jagalactic.com Subject: [PATCH 4/9] drivers/cxl,dax: add dax driver mode selection for dax regions Date: Thu, 29 Jan 2026 16:04:37 -0500 Message-ID: <20260129210442.3951412-5-gourry@gourry.net> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260129210442.3951412-1-gourry@gourry.net> References: <20260129210442.3951412-1-gourry@gourry.net> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" CXL regions may wish not to auto-configure their memory as dax kmem, but the current plumbing defaults all cxl-created dax devices to the kmem driver. This exposes them to hotplug policy, even if the user intends to use the memory as a dax device. Add plumbing to allow CXL drivers to select whether a DAX region should default to kmem (DAXDRV_KMEM_TYPE) or device (DAXDRV_DEVICE_TYPE). Add a 'dax_driver' field to struct cxl_dax_region and update devm_cxl_add_dax_region() to take a dax_driver_type parameter. In drivers/dax/cxl.c, the IORESOURCE_DAX_KMEM flag used by dax driver matching code is now set conditionally based on dax_region->dax_driver. Exports `enum dax_driver_type` to linux/dax.h for use in the cxl driver. All current callers pass DAXDRV_KMEM_TYPE for backward compatibility. Cc: John Groves Signed-off-by: Gregory Price Reviewed-by: Jonathan Cameron --- drivers/cxl/core/core.h | 1 + drivers/cxl/core/region.c | 6 ++++-- drivers/cxl/cxl.h | 2 ++ drivers/dax/bus.h | 6 +----- drivers/dax/cxl.c | 6 +++++- include/linux/dax.h | 5 +++++ 6 files changed, 18 insertions(+), 8 deletions(-) diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h index 1fb66132b777..dd987ef2def5 100644 --- a/drivers/cxl/core/core.h +++ b/drivers/cxl/core/core.h @@ -6,6 +6,7 @@ =20 #include #include +#include =20 extern const struct device_type cxl_nvdimm_bridge_type; extern const struct device_type cxl_nvdimm_type; diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c index eef5d5fe3f95..e4097c464ed3 100644 --- a/drivers/cxl/core/region.c +++ b/drivers/cxl/core/region.c @@ -3450,7 +3450,8 @@ static void cxlr_dax_unregister(void *_cxlr_dax) device_unregister(&cxlr_dax->dev); } =20 -static int devm_cxl_add_dax_region(struct cxl_region *cxlr) +static int devm_cxl_add_dax_region(struct cxl_region *cxlr, + enum dax_driver_type dax_driver) { struct cxl_dax_region *cxlr_dax; struct device *dev; @@ -3461,6 +3462,7 @@ static int devm_cxl_add_dax_region(struct cxl_region = *cxlr) return PTR_ERR(cxlr_dax); =20 cxlr_dax->online_type =3D mhp_get_default_online_type(); + cxlr_dax->dax_driver =3D dax_driver; dev =3D &cxlr_dax->dev; rc =3D dev_set_name(dev, "dax_region%d", cxlr->id); if (rc) @@ -3994,7 +3996,7 @@ static int cxl_region_probe(struct device *dev) p->res->start, p->res->end, cxlr, is_system_ram) > 0) return 0; - return devm_cxl_add_dax_region(cxlr); + return devm_cxl_add_dax_region(cxlr, DAXDRV_KMEM_TYPE); default: dev_dbg(&cxlr->dev, "unsupported region mode: %d\n", cxlr->mode); diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h index 07d57d13f4c7..c06a239c0008 100644 --- a/drivers/cxl/cxl.h +++ b/drivers/cxl/cxl.h @@ -12,6 +12,7 @@ #include #include #include +#include =20 extern const struct nvdimm_security_ops *cxl_security_ops; =20 @@ -592,6 +593,7 @@ struct cxl_dax_region { struct cxl_region *cxlr; struct range hpa_range; int online_type; /* MMOP_ value for kmem driver */ + enum dax_driver_type dax_driver; }; =20 /** diff --git a/drivers/dax/bus.h b/drivers/dax/bus.h index 4ac92a4edfe7..9144593b4029 100644 --- a/drivers/dax/bus.h +++ b/drivers/dax/bus.h @@ -2,6 +2,7 @@ /* Copyright(c) 2016 - 2018 Intel Corporation. All rights reserved. */ #ifndef __DAX_BUS_H__ #define __DAX_BUS_H__ +#include #include #include =20 @@ -29,11 +30,6 @@ struct dev_dax_data { =20 struct dev_dax *devm_create_dev_dax(struct dev_dax_data *data); =20 -enum dax_driver_type { - DAXDRV_KMEM_TYPE, - DAXDRV_DEVICE_TYPE, -}; - struct dax_device_driver { struct device_driver drv; struct list_head ids; diff --git a/drivers/dax/cxl.c b/drivers/dax/cxl.c index 856a0cd24f3b..b13ecc2f9806 100644 --- a/drivers/dax/cxl.c +++ b/drivers/dax/cxl.c @@ -11,14 +11,18 @@ static int cxl_dax_region_probe(struct device *dev) struct cxl_dax_region *cxlr_dax =3D to_cxl_dax_region(dev); int nid =3D phys_to_target_node(cxlr_dax->hpa_range.start); struct cxl_region *cxlr =3D cxlr_dax->cxlr; + unsigned long flags =3D 0; struct dax_region *dax_region; struct dev_dax_data data; =20 + if (cxlr_dax->dax_driver =3D=3D DAXDRV_KMEM_TYPE) + flags |=3D IORESOURCE_DAX_KMEM; + if (nid =3D=3D NUMA_NO_NODE) nid =3D memory_add_physaddr_to_nid(cxlr_dax->hpa_range.start); =20 dax_region =3D alloc_dax_region(dev, cxlr->id, &cxlr_dax->hpa_range, nid, - PMD_SIZE, IORESOURCE_DAX_KMEM); + PMD_SIZE, flags); if (!dax_region) return -ENOMEM; =20 diff --git a/include/linux/dax.h b/include/linux/dax.h index bf103f317cac..e62f92d0ace1 100644 --- a/include/linux/dax.h +++ b/include/linux/dax.h @@ -19,6 +19,11 @@ enum dax_access_mode { DAX_RECOVERY_WRITE, }; =20 +enum dax_driver_type { + DAXDRV_KMEM_TYPE, + DAXDRV_DEVICE_TYPE, +}; + struct dax_operations { /* * direct_access: translate a device-relative --=20 2.52.0