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[173.79.60.52]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-51a51ae8ee7sm49502301cf.24.2026.06.24.07.58.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 24 Jun 2026 07:58:07 -0700 (PDT) From: Gregory Price To: linux-mm@kvack.org, nvdimm@lists.linux.dev Cc: linux-kernel@vger.kernel.org, linux-cxl@vger.kernel.org, driver-core@lists.linux.dev, linux-kselftest@vger.kernel.org, kernel-team@meta.com, david@kernel.org, osalvador@suse.de, gregkh@linuxfoundation.org, rafael@kernel.org, dakr@kernel.org, djbw@kernel.org, vishal.l.verma@intel.com, dave.jiang@intel.com, akpm@linux-foundation.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, shuah@kernel.org, gourry@gourry.net, alison.schofield@intel.com, Smita.KoralahalliChannabasappa@amd.com, ira.weiny@intel.com, apopple@nvidia.com Subject: [PATCH v5 6/9] dax: plumb hotplug online_type through dax Date: Wed, 24 Jun 2026 10:57:41 -0400 Message-ID: <20260624145744.3532049-7-gourry@gourry.net> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260624145744.3532049-1-gourry@gourry.net> References: <20260624145744.3532049-1-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: 8bit There is no way for drivers leveraging dax_kmem to plumb through a preferred auto-online policy - the system default policy is forced. Add 'enum mmop' field to DAX device creation path to allow drivers to specify an auto-online policy when using the kmem driver. Capturing the system default would otherwise break the ABI, because the system default can change - but we would be statically assigning the value at device creation time. To resolve this we add DAX_ONLINE_DEFAULT, which defaults devices to the current behavior, while providing a clean way to override it. No behavioural change for existing callers (still the system default). Signed-off-by: Gregory Price --- drivers/dax/bus.c | 3 +++ drivers/dax/bus.h | 9 +++++++++ drivers/dax/cxl.c | 1 + drivers/dax/dax-private.h | 4 ++++ drivers/dax/hmem/hmem.c | 1 + drivers/dax/kmem.c | 11 +++++++++-- drivers/dax/pmem.c | 1 + 7 files changed, 28 insertions(+), 2 deletions(-) diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c index 492573b47f66..4a03b323b003 100644 --- a/drivers/dax/bus.c +++ b/drivers/dax/bus.c @@ -1,6 +1,7 @@ // SPDX-License-Identifier: GPL-2.0 /* Copyright(c) 2017-2018 Intel Corporation. All rights reserved. */ #include +#include #include #include #include @@ -394,6 +395,7 @@ static ssize_t create_store(struct device *dev, struct device_attribute *attr, .size = 0, .id = -1, .memmap_on_memory = false, + .online_type = DAX_ONLINE_DEFAULT, }; struct dev_dax *dev_dax = __devm_create_dev_dax(&data); @@ -1527,6 +1529,7 @@ static struct dev_dax *__devm_create_dev_dax(struct dev_dax_data *data) ida_init(&dev_dax->ida); dev_dax->memmap_on_memory = data->memmap_on_memory; + dev_dax->online_type = data->online_type; inode = dax_inode(dax_dev); dev->devt = inode->i_rdev; diff --git a/drivers/dax/bus.h b/drivers/dax/bus.h index 5909171a4428..f3c9dae5de6b 100644 --- a/drivers/dax/bus.h +++ b/drivers/dax/bus.h @@ -3,6 +3,7 @@ #ifndef __DAX_BUS_H__ #define __DAX_BUS_H__ #include +#include #include #include #include @@ -16,6 +17,13 @@ struct dax_region; #define IORESOURCE_DAX_STATIC BIT(0) #define IORESOURCE_DAX_KMEM BIT(1) +/* + * online_type sentinel: the device was created without an explicit online + * policy, so the system default is resolved when the kmem driver binds, + * (not at device-creation time, which would freeze a stale policy). + */ +#define DAX_ONLINE_DEFAULT (-1) + struct dax_region *alloc_dax_region(struct device *parent, int region_id, struct range *range, int target_node, unsigned int align, unsigned long flags); @@ -26,6 +34,7 @@ struct dev_dax_data { resource_size_t size; int id; bool memmap_on_memory; + enum mmop online_type; }; struct dev_dax *devm_create_dev_dax(struct dev_dax_data *data); diff --git a/drivers/dax/cxl.c b/drivers/dax/cxl.c index 3ab39b77843d..1a7ec6212213 100644 --- a/drivers/dax/cxl.c +++ b/drivers/dax/cxl.c @@ -27,6 +27,7 @@ static int cxl_dax_region_probe(struct device *dev) .id = -1, .size = range_len(&cxlr_dax->hpa_range), .memmap_on_memory = true, + .online_type = DAX_ONLINE_DEFAULT, }; return PTR_ERR_OR_ZERO(devm_create_dev_dax(&data)); diff --git a/drivers/dax/dax-private.h b/drivers/dax/dax-private.h index 81e4af49e39c..ccd77965fe3e 100644 --- a/drivers/dax/dax-private.h +++ b/drivers/dax/dax-private.h @@ -8,6 +8,7 @@ #include #include #include +#include /* private routines between core files */ struct dax_device; @@ -79,6 +80,8 @@ struct dev_dax_range { * @dev: device core * @pgmap: pgmap for memmap setup / lifetime (driver owned) * @memmap_on_memory: allow kmem to put the memmap in the memory + * @online_type: MMOP_* online type for memory hotplug, or DAX_ONLINE_DEFAULT + * to resolve the system default policy when kmem binds * @nr_range: size of @ranges * @ranges: range tuples of memory used */ @@ -95,6 +98,7 @@ struct dev_dax { struct device dev; struct dev_pagemap *pgmap; bool memmap_on_memory; + enum mmop online_type; int nr_range; struct dev_dax_range *ranges; }; diff --git a/drivers/dax/hmem/hmem.c b/drivers/dax/hmem/hmem.c index af21f66bf872..2de3bc925172 100644 --- a/drivers/dax/hmem/hmem.c +++ b/drivers/dax/hmem/hmem.c @@ -37,6 +37,7 @@ static int dax_hmem_probe(struct platform_device *pdev) .id = -1, .size = region_idle ? 0 : range_len(&mri->range), .memmap_on_memory = false, + .online_type = DAX_ONLINE_DEFAULT, }; return PTR_ERR_OR_ZERO(devm_create_dev_dax(&data)); diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c index 592171ec10f4..0a184c0878dd 100644 --- a/drivers/dax/kmem.c +++ b/drivers/dax/kmem.c @@ -72,6 +72,7 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax) int i, rc, mapped = 0; mhp_t mhp_flags; int numa_node; + int online_type; int adist = MEMTIER_DEFAULT_DAX_ADISTANCE; /* @@ -132,6 +133,11 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax) goto err_reg_mgid; data->mgid = rc; + /* Resolve system default at bind time in case it changed */ + online_type = dev_dax->online_type; + if (online_type == DAX_ONLINE_DEFAULT) + online_type = mhp_get_default_online_type(); + for (i = 0; i < dev_dax->nr_range; i++) { struct resource *res; struct range range; @@ -172,8 +178,9 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax) * Ensure that future kexec'd kernels will not treat * this as RAM automatically. */ - rc = add_memory_driver_managed(data->mgid, range.start, - range_len(&range), kmem_name, mhp_flags); + rc = __add_memory_driver_managed(data->mgid, range.start, + range_len(&range), kmem_name, mhp_flags, + online_type); if (rc) { dev_warn(dev, "mapping%d: %#llx-%#llx memory add failed\n", diff --git a/drivers/dax/pmem.c b/drivers/dax/pmem.c index bee93066a849..e7adace69195 100644 --- a/drivers/dax/pmem.c +++ b/drivers/dax/pmem.c @@ -63,6 +63,7 @@ static struct dev_dax *__dax_pmem_probe(struct device *dev) .pgmap = &pgmap, .size = range_len(&range), .memmap_on_memory = false, + .online_type = DAX_ONLINE_DEFAULT, }; return devm_create_dev_dax(&data); -- 2.54.0