From: Dan Williams Date: Fri, 27 Mar 2026 05:28:18 +0000 (-0700) Subject: dax/hmem: Fix singleton confusion between dax_hmem_work and hmem devices X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=f8dc1bde187310e0345beb08df949e0c2a4c86ce;p=thirdparty%2Fkernel%2Flinux.git dax/hmem: Fix singleton confusion between dax_hmem_work and hmem devices dax_hmem (ab)uses a platform device to allow for a module to autoload in the presence of "Soft Reserved" resources. The dax_hmem driver had no dependencies on the "hmem_platform" device being a singleton until the recent "dax_hmem vs dax_cxl" takeover solution. Replace the layering violation of dax_hmem_work assuming that there will never be more than one "hmem_platform" device associated with a global work item with a dax_hmem local workqueue that can theoretically support any number of hmem_platform devices. Fixup the reference counting to only pin the device while it is live in the queue. Signed-off-by: Dan Williams Reviewed-by: Ira Weiny Reviewed-by: Alison Schofield Reviewed-by: Dave Jiang Link: https://patch.msgid.link/20260327052821.440749-7-dan.j.williams@intel.com Signed-off-by: Dave Jiang --- diff --git a/drivers/dax/bus.h b/drivers/dax/bus.h index ebbfe2d6da14..7b1a83f1ce1f 100644 --- a/drivers/dax/bus.h +++ b/drivers/dax/bus.h @@ -3,7 +3,9 @@ #ifndef __DAX_BUS_H__ #define __DAX_BUS_H__ #include +#include #include +#include struct dev_dax; struct resource; @@ -49,8 +51,19 @@ void dax_driver_unregister(struct dax_device_driver *dax_drv); void kill_dev_dax(struct dev_dax *dev_dax); bool static_dev_dax(struct dev_dax *dev_dax); +struct hmem_platform_device { + struct platform_device pdev; + struct work_struct work; + bool did_probe; +}; + +static inline struct hmem_platform_device * +to_hmem_platform_device(struct platform_device *pdev) +{ + return container_of(pdev, struct hmem_platform_device, pdev); +} + #if IS_ENABLED(CONFIG_DEV_DAX_HMEM) -extern bool dax_hmem_initial_probe; void dax_hmem_flush_work(void); #else static inline void dax_hmem_flush_work(void) { } diff --git a/drivers/dax/hmem/device.c b/drivers/dax/hmem/device.c index 675d56276d78..d70359b4307b 100644 --- a/drivers/dax/hmem/device.c +++ b/drivers/dax/hmem/device.c @@ -4,13 +4,11 @@ #include #include #include +#include "../bus.h" static bool nohmem; module_param_named(disable, nohmem, bool, 0444); -bool dax_hmem_initial_probe; -EXPORT_SYMBOL_FOR_MODULES(dax_hmem_initial_probe, "dax_hmem"); - static bool platform_initialized; static DEFINE_MUTEX(hmem_resource_lock); static struct resource hmem_active = { @@ -36,9 +34,21 @@ int walk_hmem_resources(struct device *host, walk_hmem_fn fn) } EXPORT_SYMBOL_GPL(walk_hmem_resources); +static void hmem_work(struct work_struct *work) +{ + /* place holder until dax_hmem driver attaches */ +} + +static struct hmem_platform_device hmem_platform = { + .pdev = { + .name = "hmem_platform", + .id = 0, + }, + .work = __WORK_INITIALIZER(hmem_platform.work, hmem_work), +}; + static void __hmem_register_resource(int target_nid, struct resource *res) { - struct platform_device *pdev; struct resource *new; int rc; @@ -54,17 +64,13 @@ static void __hmem_register_resource(int target_nid, struct resource *res) if (platform_initialized) return; - pdev = platform_device_alloc("hmem_platform", 0); - if (!pdev) { + rc = platform_device_register(&hmem_platform.pdev); + if (rc) { pr_err_once("failed to register device-dax hmem_platform device\n"); return; } - rc = platform_device_add(pdev); - if (rc) - platform_device_put(pdev); - else - platform_initialized = true; + platform_initialized = true; } void hmem_register_resource(int target_nid, struct resource *res) diff --git a/drivers/dax/hmem/hmem.c b/drivers/dax/hmem/hmem.c index dd3d7f93baee..e1dae83dae8d 100644 --- a/drivers/dax/hmem/hmem.c +++ b/drivers/dax/hmem/hmem.c @@ -59,20 +59,11 @@ static void release_hmem(void *pdev) platform_device_unregister(pdev); } -struct dax_defer_work { - struct platform_device *pdev; - struct work_struct work; -}; - -static void process_defer_work(struct work_struct *w); - -static struct dax_defer_work dax_hmem_work = { - .work = __WORK_INITIALIZER(dax_hmem_work.work, process_defer_work), -}; +static struct workqueue_struct *dax_hmem_wq; void dax_hmem_flush_work(void) { - flush_work(&dax_hmem_work.work); + flush_workqueue(dax_hmem_wq); } EXPORT_SYMBOL_FOR_MODULES(dax_hmem_flush_work, "dax_cxl"); @@ -134,24 +125,6 @@ out_put: return rc; } -static int hmem_register_device(struct device *host, int target_nid, - const struct resource *res) -{ - if (IS_ENABLED(CONFIG_DEV_DAX_CXL) && - region_intersects(res->start, resource_size(res), IORESOURCE_MEM, - IORES_DESC_CXL) != REGION_DISJOINT) { - if (!dax_hmem_initial_probe) { - dev_dbg(host, "await CXL initial probe: %pr\n", res); - queue_work(system_long_wq, &dax_hmem_work.work); - return 0; - } - dev_dbg(host, "deferring range to CXL: %pr\n", res); - return 0; - } - - return __hmem_register_device(host, target_nid, res); -} - static int hmem_register_cxl_device(struct device *host, int target_nid, const struct resource *res) { @@ -170,35 +143,55 @@ static int hmem_register_cxl_device(struct device *host, int target_nid, static void process_defer_work(struct work_struct *w) { - struct dax_defer_work *work = container_of(w, typeof(*work), work); - struct platform_device *pdev; - - if (!work->pdev) - return; - - pdev = work->pdev; + struct hmem_platform_device *hpdev = container_of(w, typeof(*hpdev), work); + struct device *dev = &hpdev->pdev.dev; /* Relies on cxl_acpi and cxl_pci having had a chance to load */ wait_for_device_probe(); - guard(device)(&pdev->dev); - if (!pdev->dev.driver) - return; + guard(device)(dev); + if (!dev->driver) + goto out; - if (!dax_hmem_initial_probe) { - dax_hmem_initial_probe = true; - walk_hmem_resources(&pdev->dev, hmem_register_cxl_device); + if (!hpdev->did_probe) { + hpdev->did_probe = true; + walk_hmem_resources(dev, hmem_register_cxl_device); } +out: + put_device(dev); +} + +static int hmem_register_device(struct device *host, int target_nid, + const struct resource *res) +{ + struct platform_device *pdev = to_platform_device(host); + struct hmem_platform_device *hpdev = to_hmem_platform_device(pdev); + + if (IS_ENABLED(CONFIG_DEV_DAX_CXL) && + region_intersects(res->start, resource_size(res), IORESOURCE_MEM, + IORES_DESC_CXL) != REGION_DISJOINT) { + if (!hpdev->did_probe) { + dev_dbg(host, "await CXL initial probe: %pr\n", res); + hpdev->work.func = process_defer_work; + get_device(host); + if (!queue_work(dax_hmem_wq, &hpdev->work)) + put_device(host); + return 0; + } + dev_dbg(host, "deferring range to CXL: %pr\n", res); + return 0; + } + + return __hmem_register_device(host, target_nid, res); } static int dax_hmem_platform_probe(struct platform_device *pdev) { - if (work_pending(&dax_hmem_work.work)) - return -EBUSY; + struct hmem_platform_device *hpdev = to_hmem_platform_device(pdev); - if (!dax_hmem_work.pdev) - dax_hmem_work.pdev = - to_platform_device(get_device(&pdev->dev)); + /* queue is only flushed on module unload, fail rebind with pending work */ + if (work_pending(&hpdev->work)) + return -EBUSY; return walk_hmem_resources(&pdev->dev, hmem_register_device); } @@ -224,26 +217,33 @@ static __init int dax_hmem_init(void) request_module("cxl_pci"); } + dax_hmem_wq = alloc_ordered_workqueue("dax_hmem_wq", 0); + if (!dax_hmem_wq) + return -ENOMEM; + rc = platform_driver_register(&dax_hmem_platform_driver); if (rc) - return rc; + goto err_platform_driver; rc = platform_driver_register(&dax_hmem_driver); if (rc) - platform_driver_unregister(&dax_hmem_platform_driver); + goto err_driver; + + return 0; + +err_driver: + platform_driver_unregister(&dax_hmem_platform_driver); +err_platform_driver: + destroy_workqueue(dax_hmem_wq); return rc; } static __exit void dax_hmem_exit(void) { - if (dax_hmem_work.pdev) { - flush_work(&dax_hmem_work.work); - put_device(&dax_hmem_work.pdev->dev); - } - platform_driver_unregister(&dax_hmem_driver); platform_driver_unregister(&dax_hmem_platform_driver); + destroy_workqueue(dax_hmem_wq); } module_init(dax_hmem_init);