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Message-ID: <591729d6-eef8-4a6d-ab01-b70270e63d1f@intel.com>
Date: Fri, 26 Sep 2025 16:02:20 -0700
From: Dave Jiang <dave.jiang@...el.com>
To: Terry Bowman <terry.bowman@....com>, dave@...olabs.net,
jonathan.cameron@...wei.com, alison.schofield@...el.com,
dan.j.williams@...el.com, bhelgaas@...gle.com, shiju.jose@...wei.com,
ming.li@...omail.com, Smita.KoralahalliChannabasappa@....com,
rrichter@....com, dan.carpenter@...aro.org,
PradeepVineshReddy.Kodamati@....com, lukas@...ner.de,
Benjamin.Cheatham@....com, sathyanarayanan.kuppuswamy@...ux.intel.com,
linux-cxl@...r.kernel.org, alucerop@....com, ira.weiny@...el.com
Cc: linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH v12 19/25] cxl: Introduce cxl_pci_drv_bound() to check for
bound driver
On 9/25/25 3:34 PM, Terry Bowman wrote:
> CXL devices handle protocol errors via driver-specific callbacks rather
> than the generic pci_driver::err_handlers by default. The callbacks are
> implemented in the cxl_pci driver and are not part of struct pci_driver, so
> cxl_core must verify that a device is actually bound to the cxl_pci
> module's driver before invoking the callbacks (the device could be bound
> to another driver, e.g. VFIO).
>
> However, cxl_core can not reference symbols in the cxl_pci module because
> it creates a circular dependency. This prevents cxl_core from checking the
> EP's bound driver and calling the callbacks.
>
> To fix this, move drivers/cxl/pci.c into drivers/cxl/core/pci_drv.c and
> build it as part of the cxl_core module. Compile into cxl_core using
> CXL_PCI and CXL_CORE Kconfig dependencies. This removes the standalone cxl_pci
> module, consolidates the cxl_pci driver code into cxl_core, and eliminates
> the circular dependency so cxl_core can safely perform bound-driver checks
> and invoke the CXL PCI callbacks.
>
> Introduce cxl_pci_drv_bound() to return boolean depending on if the PCI EP
> parameter is bound to a CXL driver instance. This will be used in future
> patch when dequeuing work from the kfifo.
>
> Signed-off-by: Terry Bowman <terry.bowman@....com>
Reviewed-by: Dave Jiang <dave.jiang@...el.com>
>
> ---
>
> Changes in v11 -> v12:
> - New patch
> ---
> drivers/cxl/Kconfig | 6 +++---
> drivers/cxl/Makefile | 2 --
> drivers/cxl/core/Makefile | 1 +
> drivers/cxl/core/core.h | 9 +++++++++
> drivers/cxl/{pci.c => core/pci_drv.c} | 16 ++++++++--------
> drivers/cxl/core/port.c | 3 +++
> 6 files changed, 24 insertions(+), 13 deletions(-)
> rename drivers/cxl/{pci.c => core/pci_drv.c} (99%)
>
> diff --git a/drivers/cxl/Kconfig b/drivers/cxl/Kconfig
> index 028201e24523..9ee76bae02d5 100644
> --- a/drivers/cxl/Kconfig
> +++ b/drivers/cxl/Kconfig
> @@ -20,7 +20,7 @@ menuconfig CXL_BUS
> if CXL_BUS
>
> config CXL_PCI
> - tristate "PCI manageability"
> + bool "PCI manageability"
> default CXL_BUS
> help
> The CXL specification defines a "CXL memory device" sub-class in the
> @@ -29,12 +29,12 @@ config CXL_PCI
> memory to be mapped into the system address map (Host-managed Device
> Memory (HDM)).
>
> - Say 'y/m' to enable a driver that will attach to CXL memory expander
> + Say 'y' to enable a driver that will attach to CXL memory expander
> devices enumerated by the memory device class code for configuration
> and management primarily via the mailbox interface. See Chapter 2.3
> Type 3 CXL Device in the CXL 2.0 specification for more details.
>
> - If unsure say 'm'.
> + If unsure say 'y'.
>
> config CXL_MEM_RAW_COMMANDS
> bool "RAW Command Interface for Memory Devices"
> diff --git a/drivers/cxl/Makefile b/drivers/cxl/Makefile
> index 2caa90fa4bf2..ff6add88b6ae 100644
> --- a/drivers/cxl/Makefile
> +++ b/drivers/cxl/Makefile
> @@ -12,10 +12,8 @@ obj-$(CONFIG_CXL_PORT) += cxl_port.o
> obj-$(CONFIG_CXL_ACPI) += cxl_acpi.o
> obj-$(CONFIG_CXL_PMEM) += cxl_pmem.o
> obj-$(CONFIG_CXL_MEM) += cxl_mem.o
> -obj-$(CONFIG_CXL_PCI) += cxl_pci.o
>
> cxl_port-y := port.o
> cxl_acpi-y := acpi.o
> cxl_pmem-y := pmem.o security.o
> cxl_mem-y := mem.o
> -cxl_pci-y := pci.o
> diff --git a/drivers/cxl/core/Makefile b/drivers/cxl/core/Makefile
> index b2930cc54f8b..91f43c3f2292 100644
> --- a/drivers/cxl/core/Makefile
> +++ b/drivers/cxl/core/Makefile
> @@ -20,3 +20,4 @@ cxl_core-$(CONFIG_CXL_MCE) += mce.o
> cxl_core-$(CONFIG_CXL_FEATURES) += features.o
> cxl_core-$(CONFIG_CXL_EDAC_MEM_FEATURES) += edac.o
> cxl_core-$(CONFIG_CXL_RAS) += ras.o
> +cxl_core-$(CONFIG_CXL_PCI) += pci_drv.o
> diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h
> index 74c64d458f12..9ceff8acf844 100644
> --- a/drivers/cxl/core/core.h
> +++ b/drivers/cxl/core/core.h
> @@ -202,4 +202,13 @@ int cxl_set_feature(struct cxl_mailbox *cxl_mbox, const uuid_t *feat_uuid,
> u16 *return_code);
> #endif
>
> +#ifdef CONFIG_CXL_PCI
> +bool cxl_pci_drv_bound(struct pci_dev *pdev);
> +int cxl_pci_driver_init(void);
> +void cxl_pci_driver_exit(void);
> +#else
> +static inline bool cxl_pci_drv_bound(struct pci_dev *pdev) { return false; };
> +static inline int cxl_pci_driver_init(void) { return 0; }
> +static inline void cxl_pci_driver_exit(void) { }
> +#endif
> #endif /* __CXL_CORE_H__ */
> diff --git a/drivers/cxl/pci.c b/drivers/cxl/core/pci_drv.c
> similarity index 99%
> rename from drivers/cxl/pci.c
> rename to drivers/cxl/core/pci_drv.c
> index 71fb8709081e..746b5017d336 100644
> --- a/drivers/cxl/pci.c
> +++ b/drivers/cxl/core/pci_drv.c
> @@ -1132,6 +1132,12 @@ static struct pci_driver cxl_pci_driver = {
> },
> };
>
> +bool cxl_pci_drv_bound(struct pci_dev *pdev)
> +{
> + return (pdev->driver == &cxl_pci_driver);
> +}
> +EXPORT_SYMBOL_NS_GPL(cxl_pci_drv_bound, "CXL");
> +
> #define CXL_EVENT_HDR_FLAGS_REC_SEVERITY GENMASK(1, 0)
> static void cxl_handle_cper_event(enum cxl_event_type ev_type,
> struct cxl_cper_event_rec *rec)
> @@ -1178,7 +1184,7 @@ static void cxl_cper_work_fn(struct work_struct *work)
> }
> static DECLARE_WORK(cxl_cper_work, cxl_cper_work_fn);
>
> -static int __init cxl_pci_driver_init(void)
> +int __init cxl_pci_driver_init(void)
> {
> int rc;
>
> @@ -1193,15 +1199,9 @@ static int __init cxl_pci_driver_init(void)
> return rc;
> }
>
> -static void __exit cxl_pci_driver_exit(void)
> +void cxl_pci_driver_exit(void)
> {
> cxl_cper_unregister_work(&cxl_cper_work);
> cancel_work_sync(&cxl_cper_work);
> pci_unregister_driver(&cxl_pci_driver);
> }
> -
> -module_init(cxl_pci_driver_init);
> -module_exit(cxl_pci_driver_exit);
> -MODULE_DESCRIPTION("CXL: PCI manageability");
> -MODULE_LICENSE("GPL v2");
> -MODULE_IMPORT_NS("CXL");
> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
> index bd4be046888a..56fa4ac33e8b 100644
> --- a/drivers/cxl/core/port.c
> +++ b/drivers/cxl/core/port.c
> @@ -2502,6 +2502,8 @@ static __init int cxl_core_init(void)
> if (rc)
> goto err_ras;
>
> + cxl_pci_driver_init();
> +
> return 0;
>
> err_ras:
> @@ -2517,6 +2519,7 @@ static __init int cxl_core_init(void)
>
> static void cxl_core_exit(void)
> {
> + cxl_pci_driver_exit();
> cxl_ras_exit();
> cxl_region_exit();
> bus_unregister(&cxl_bus_type);
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