Re: [PATCH] cxl: Adjust the startup priority of cxl_pmem to be higher than that of cxl_acpi

[Dave Jiang]

On 3/19/26 1:40 PM, Dan Williams wrote:
> Cui Chao wrote:
> 
> Hi Cui, this looks good, a few notes below.
> 
>> During the cxl_acpi probe process, it checks whether the cxl_nvb device
>> and driver have been attached. Currently, the startup priority of the
>> cxl_pmem driver is lower than that of the cxl_acpi driver. At this point,
>> the cxl_nvb driver has not yet been registered on the cxl_bus, causing
>> the attachment check to fail. This results in a failure to add the root
>> nvdimm bridge, leading to a cxl_acpi probe failure and ultimately
>> affecting the subsequent loading of cxl drivers. As a consequence, only
>> one mem device object exists on the cxl_bus, while the cxl_port device
>> objects and decoder device objects are missing.
>>
>> The solution is to raise the startup priority of cxl_pmem to be higher
>> than that of cxl_acpi, ensuring that the cxl_pmem driver is registered
>> before the aforementioned attachment check occurs.
> 
> Missing:
> 
> Fixes: e7e222ad73d9 ("cxl: Move devm_cxl_add_nvdimm_bridge() to cxl_pmem.ko")
> 
>> Co-developed-by: Wang Yinfeng <wangyinfeng@xxxxxxxxxxxxxx>
>> Signed-off-by: Wang Yinfeng <wangyinfeng@xxxxxxxxxxxxxx>
>> Signed-off-by: Cui Chao <cuichao1753@xxxxxxxxxxxxxx>
>> ---
>>  drivers/cxl/pmem.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/cxl/pmem.c b/drivers/cxl/pmem.c
>> index 082ec0f1c3a0..261dff7ced9f 100644
>> --- a/drivers/cxl/pmem.c
>> +++ b/drivers/cxl/pmem.c
>> @@ -554,7 +554,7 @@ static __exit void cxl_pmem_exit(void)
>>  
>>  MODULE_DESCRIPTION("CXL PMEM: Persistent Memory Support");
>>  MODULE_LICENSE("GPL v2");
>> -module_init(cxl_pmem_init);
>> +subsys_initcall(cxl_pmem_init);
> 
> Yes, this is a problem, but longer term I do not think we want to get
> into this game of different initcall levels for different modules, and
> dispersing the documentation for all these concerns.
> 
> So I want to match the initcall level of cxl_acpi and move the init
> order management to the Makefile to disambiguate which initialization
> happens first for the same level. There is already some documentation in
> the Makefile about this case.
> 
> This matches what happens with all the other CXL modules that share
> "module_init()", but fallback to Makefile order when built-in.
> 
> Specifically what I am proposing is a patch like below. However, my
> change change is not suitable for v7.0-rc which can take your one-line
> fix. So, for that you can add:
> 
> Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx>

Applied to cxl/fixes
be5c5280cf2b ("cxl: Adjust the startup priority of cxl_pmem to be higher than that of cxl_acpi")

Do you want to submit the patch below for 7.1 cxl/next?

DJ


> 
> ...and then I will follow up to move it to the new proposed scheme:
> 
> -- 8< --
> Subject: cxl: Introduce cxl_subsys_initcall
> 
> From: Dan Williams <dan.j.williams@xxxxxxxxx>
> 
> Create a single definition of the early initcall expectation
> of the CXL subsystem. Use that single definition to collect all the
> documentation about how to order dependencies both within the subsystem
> (drivers/cxl/Makefile order) and outside the subsystem (producer / consumer
> dependencies).
> 
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> ---
>  drivers/cxl/Makefile    |    4 +++-
>  drivers/cxl/acpi.c      |    7 +------
>  drivers/cxl/core/port.c |    2 +-
>  drivers/cxl/cxl.h       |   10 ++++++++++
>  drivers/cxl/pmem.c      |    2 +-
>  drivers/cxl/port.c      |    6 +-----
>  6 files changed, 17 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/cxl/Makefile b/drivers/cxl/Makefile
> index 2caa90fa4bf2..d449bffde205 100644
> --- a/drivers/cxl/Makefile
> +++ b/drivers/cxl/Makefile
> @@ -7,6 +7,8 @@
>  # - 'mem' and 'pmem' before endpoint drivers so that memdevs are
>  #   immediately enabled
>  # - 'pci' last, also mirrors the hardware enumeration hierarchy
> +# - 'pmem' before 'acpi' because acpi wants to create cxl_nvdimm_bridge
> +#   devices
>  obj-y += core/
>  obj-$(CONFIG_CXL_PORT) += cxl_port.o
>  obj-$(CONFIG_CXL_ACPI) += cxl_acpi.o
> @@ -15,7 +17,7 @@ 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_acpi-y := acpi.o
>  cxl_mem-y := mem.o
>  cxl_pci-y := pci.o
> diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
> index 127537628817..6d158c7b6ca7 100644
> --- a/drivers/cxl/acpi.c
> +++ b/drivers/cxl/acpi.c
> @@ -995,12 +995,7 @@ static void __exit cxl_acpi_exit(void)
>  	cxl_bus_drain();
>  }
>  
> -/*
> - * Load before dax_hmem sees 'Soft Reserved' CXL ranges. Use
> - * subsys_initcall_sync() since there is an order dependency with
> - * subsys_initcall(efisubsys_init), which must run first.
> - */
> -subsys_initcall_sync(cxl_acpi_init);
> +cxl_subsys_initcall(cxl_acpi_init);
>  
>  /*
>   * Arrange for host-bridge ports to be active synchronous with
> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
> index 0c5957d1d329..aca31cdbc5a3 100644
> --- a/drivers/cxl/core/port.c
> +++ b/drivers/cxl/core/port.c
> @@ -2549,7 +2549,7 @@ static void cxl_core_exit(void)
>  	debugfs_remove_recursive(cxl_debugfs);
>  }
>  
> -subsys_initcall(cxl_core_init);
> +cxl_subsys_initcall(cxl_core_init);
>  module_exit(cxl_core_exit);
>  MODULE_DESCRIPTION("CXL: Core Compute Express Link support");
>  MODULE_LICENSE("GPL v2");
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index 9b947286eb9b..53086757cc56 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -909,6 +909,16 @@ void cxl_driver_unregister(struct cxl_driver *cxl_drv);
>  #define module_cxl_driver(__cxl_driver) \
>  	module_driver(__cxl_driver, cxl_driver_register, cxl_driver_unregister)
>  
> +/*
> + * When built-in, some CXL modules need to load before others, see
> + * drivers/cxl/Makefile for that order.
> + *
> + * CXL has init dependencies with other subsystems. It consumes EFI runtime
> + * services (subsys_initcall), it produces IORES_DESC_CXL for dax_hmem to
> + * consume (device_initcall)
> + */
> +#define cxl_subsys_initcall subsys_initcall_sync
> +
>  #define CXL_DEVICE_NVDIMM_BRIDGE	1
>  #define CXL_DEVICE_NVDIMM		2
>  #define CXL_DEVICE_PORT			3
> diff --git a/drivers/cxl/pmem.c b/drivers/cxl/pmem.c
> index 082ec0f1c3a0..d5c5ffc72e17 100644
> --- a/drivers/cxl/pmem.c
> +++ b/drivers/cxl/pmem.c
> @@ -554,7 +554,7 @@ static __exit void cxl_pmem_exit(void)
>  
>  MODULE_DESCRIPTION("CXL PMEM: Persistent Memory Support");
>  MODULE_LICENSE("GPL v2");
> -module_init(cxl_pmem_init);
> +cxl_subsys_initcall(cxl_pmem_init);
>  module_exit(cxl_pmem_exit);
>  MODULE_IMPORT_NS("CXL");
>  MODULE_ALIAS_CXL(CXL_DEVICE_NVDIMM_BRIDGE);
> diff --git a/drivers/cxl/port.c b/drivers/cxl/port.c
> index ada51948d52f..4c1385953801 100644
> --- a/drivers/cxl/port.c
> +++ b/drivers/cxl/port.c
> @@ -326,11 +326,7 @@ static int __init cxl_port_init(void)
>  {
>  	return cxl_driver_register(&cxl_port_driver);
>  }
> -/*
> - * Be ready to immediately enable ports emitted by the platform CXL root
> - * (e.g. cxl_acpi) when CONFIG_CXL_PORT=y.
> - */
> -subsys_initcall(cxl_port_init);
> +cxl_subsys_initcall(cxl_port_init);
>  
>  static void __exit cxl_port_exit(void)
>  {