From 1f1cb7f0c25574cf51501f8c8cece0047d7e8848 Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Mon, 15 Dec 2025 16:56:12 -0800 Subject: [PATCH] cxl/mem: Arrange for always-synchronous memdev attach In preparation for CXL accelerator drivers that have a hard dependency on CXL capability initialization, arrange for cxl_mem_probe() to always run synchronous with the device_add() of cxl_memdev instances. I.e. cxl_mem_driver registration is always complete before the first memdev creation event. At present, cxl_pci does not care about the attach state of the cxl_memdev because all generic memory expansion functionality can be handled by the cxl_core. For accelerators, however, that driver needs to perform driver specific initialization if CXL is available, or execute a fallback to PCIe only operation. This synchronous attach guarantee is also needed for Soft Reserve Recovery, which is an effort that needs to assert that devices have had a chance to attach before making a go / no-go decision on proceeding with CXL subsystem initialization. By moving devm_cxl_add_memdev() to cxl_mem.ko it removes async module loading as one reason that a memdev may not be attached upon return from devm_cxl_add_memdev(). Cc: Smita Koralahalli Cc: Alejandro Lucero Reviewed-by: Jonathan Cameron Tested-by: Alison Schofield Reviewed-by: Alison Schofield Reviewed-by: Ben Cheatham Reviewed-by: Dave Jiang Tested-by: Alejandro Lucero Link: https://patch.msgid.link/20251216005616.3090129-3-dan.j.williams@intel.com Signed-off-by: Dan Williams Signed-off-by: Dave Jiang --- drivers/cxl/Kconfig | 2 +- drivers/cxl/core/memdev.c | 10 +++++++--- drivers/cxl/cxlmem.h | 2 ++ drivers/cxl/mem.c | 17 +++++++++++++++++ 4 files changed, 27 insertions(+), 4 deletions(-) diff --git a/drivers/cxl/Kconfig b/drivers/cxl/Kconfig index 48b7314afdb88..f1361ed6a0d48 100644 --- a/drivers/cxl/Kconfig +++ b/drivers/cxl/Kconfig @@ -22,6 +22,7 @@ if CXL_BUS config CXL_PCI tristate "PCI manageability" default CXL_BUS + select CXL_MEM help The CXL specification defines a "CXL memory device" sub-class in the PCI "memory controller" base class of devices. Device's identified by @@ -89,7 +90,6 @@ config CXL_PMEM config CXL_MEM tristate "CXL: Memory Expansion" - depends on CXL_PCI default CXL_BUS help The CXL.mem protocol allows a device to act as a provider of "System diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c index 4dff7f44d908e..7a4153e1c6a78 100644 --- a/drivers/cxl/core/memdev.c +++ b/drivers/cxl/core/memdev.c @@ -1050,8 +1050,12 @@ static const struct file_operations cxl_memdev_fops = { .llseek = noop_llseek, }; -struct cxl_memdev *devm_cxl_add_memdev(struct device *host, - struct cxl_dev_state *cxlds) +/* + * Core helper for devm_cxl_add_memdev() that wants to both create a device and + * assert to the caller that upon return cxl_mem::probe() has been invoked. + */ +struct cxl_memdev *__devm_cxl_add_memdev(struct device *host, + struct cxl_dev_state *cxlds) { struct cxl_memdev *cxlmd; struct device *dev; @@ -1093,7 +1097,7 @@ err: put_device(dev); return ERR_PTR(rc); } -EXPORT_SYMBOL_NS_GPL(devm_cxl_add_memdev, "CXL"); +EXPORT_SYMBOL_FOR_MODULES(__devm_cxl_add_memdev, "cxl_mem"); static void sanitize_teardown_notifier(void *data) { diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h index c12ab4fc95123..012e68acad342 100644 --- a/drivers/cxl/cxlmem.h +++ b/drivers/cxl/cxlmem.h @@ -95,6 +95,8 @@ static inline bool is_cxl_endpoint(struct cxl_port *port) return is_cxl_memdev(port->uport_dev); } +struct cxl_memdev *__devm_cxl_add_memdev(struct device *host, + struct cxl_dev_state *cxlds); struct cxl_memdev *devm_cxl_add_memdev(struct device *host, struct cxl_dev_state *cxlds); int devm_cxl_sanitize_setup_notifier(struct device *host, diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c index 6e6777b7bafb5..55883797ab2db 100644 --- a/drivers/cxl/mem.c +++ b/drivers/cxl/mem.c @@ -201,6 +201,22 @@ static int cxl_mem_probe(struct device *dev) return devm_add_action_or_reset(dev, enable_suspend, NULL); } +/** + * devm_cxl_add_memdev - Add a CXL memory device + * @host: devres alloc/release context and parent for the memdev + * @cxlds: CXL device state to associate with the memdev + * + * Upon return the device will have had a chance to attach to the + * cxl_mem driver, but may fail if the CXL topology is not ready + * (hardware CXL link down, or software platform CXL root not attached) + */ +struct cxl_memdev *devm_cxl_add_memdev(struct device *host, + struct cxl_dev_state *cxlds) +{ + return __devm_cxl_add_memdev(host, cxlds); +} +EXPORT_SYMBOL_NS_GPL(devm_cxl_add_memdev, "CXL"); + static ssize_t trigger_poison_list_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t len) @@ -248,6 +264,7 @@ static struct cxl_driver cxl_mem_driver = { .probe = cxl_mem_probe, .id = CXL_DEVICE_MEMORY_EXPANDER, .drv = { + .probe_type = PROBE_FORCE_SYNCHRONOUS, .dev_groups = cxl_mem_groups, }, }; -- 2.47.3