Re: [PATCH v2 3/4] dax: Update hmem resource/device registration

["Fontenot, Nathan" <nafonten@amd.com>]

On 1/16/2025 4:28 PM, Ira Weiny wrote:
> Nathan Fontenot wrote:
>> In order to handle registering hmem devices for SOFT RESERVE reources
>                                                               ^^^^^^^^^
>                                                               resources
> 
>> that are added late in boot update the hmem_register_resource(),
>> hmem_register_device(), and walk_hmem_resources() interfaces.
>>
>> Remove the target_nid arg to hmem_register_resource(). The target nid
>> value is calculated from the resource start address and not used until
>> registering a device for the resource. Move the target nid calculation
>> to hmem_register_device().
>>
>> To allow for registering hmem devices outside of the hmem dax driver
>> probe routine save the dax hmem platform driver during probe. The
>> hmem_register_device() interface can then drop the host and target
>> nid parameters.
>>
>> There should be no functional changes.
>>
>> Signed-off-by: Nathan Fontenot <nathan.fontenot@amd.com>
>> ---
>>  drivers/acpi/numa/hmat.c  |  7 ++-----
>>  drivers/dax/hmem/device.c | 14 ++++++--------
>>  drivers/dax/hmem/hmem.c   | 12 ++++++++----
>>  include/linux/dax.h       |  9 ++++-----
>>  4 files changed, 20 insertions(+), 22 deletions(-)
>>
>> diff --git a/drivers/acpi/numa/hmat.c b/drivers/acpi/numa/hmat.c
>> index 1a902a02390f..23d4b3ad6d88 100644
>> --- a/drivers/acpi/numa/hmat.c
>> +++ b/drivers/acpi/numa/hmat.c
>> @@ -857,11 +857,8 @@ static void hmat_register_target_devices(struct memory_target *target)
>>  	if (!IS_ENABLED(CONFIG_DEV_DAX_HMEM))
>>  		return;
>>  
>> -	for (res = target->memregions.child; res; res = res->sibling) {
>> -		int target_nid = pxm_to_node(target->memory_pxm);
>> -
>> -		hmem_register_resource(target_nid, res);
>> -	}
>> +	for (res = target->memregions.child; res; res = res->sibling)
>> +		hmem_register_resource(res);
>>  }
>>  
>>  static void hmat_register_target(struct memory_target *target)
>> diff --git a/drivers/dax/hmem/device.c b/drivers/dax/hmem/device.c
>> index f9e1a76a04a9..ae25e08a636f 100644
>> --- a/drivers/dax/hmem/device.c
>> +++ b/drivers/dax/hmem/device.c
>> @@ -17,14 +17,14 @@ static struct resource hmem_active = {
>>  	.flags = IORESOURCE_MEM,
>>  };
>>  
>> -int walk_hmem_resources(struct device *host, walk_hmem_fn fn)
>> +int walk_hmem_resources(walk_hmem_fn fn)
>>  {
>>  	struct resource *res;
>>  	int rc = 0;
>>  
>>  	mutex_lock(&hmem_resource_lock);
>>  	for (res = hmem_active.child; res; res = res->sibling) {
>> -		rc = fn(host, (int) res->desc, res);
>> +		rc = fn(res);
>>  		if (rc)
>>  			break;
>>  	}
>> @@ -33,7 +33,7 @@ int walk_hmem_resources(struct device *host, walk_hmem_fn fn)
>>  }
>>  EXPORT_SYMBOL_GPL(walk_hmem_resources);
>>  
>> -static void __hmem_register_resource(int target_nid, struct resource *res)
>> +static void __hmem_register_resource(struct resource *res)
>>  {
>>  	struct platform_device *pdev;
>>  	struct resource *new;
>> @@ -46,8 +46,6 @@ static void __hmem_register_resource(int target_nid, struct resource *res)
>>  		return;
>>  	}
>>  
>> -	new->desc = target_nid;
>> -
>>  	if (platform_initialized)
>>  		return;
>>  
>> @@ -64,19 +62,19 @@ static void __hmem_register_resource(int target_nid, struct resource *res)
>>  		platform_initialized = true;
>>  }
>>  
>> -void hmem_register_resource(int target_nid, struct resource *res)
>> +void hmem_register_resource(struct resource *res)
>>  {
>>  	if (nohmem)
>>  		return;
>>  
>>  	mutex_lock(&hmem_resource_lock);
>> -	__hmem_register_resource(target_nid, res);
>> +	__hmem_register_resource(res);
>>  	mutex_unlock(&hmem_resource_lock);
>>  }
>>  
>>  static __init int hmem_register_one(struct resource *res, void *data)
>>  {
>> -	hmem_register_resource(phys_to_target_node(res->start), res);
>> +	hmem_register_resource(res);
>>  
>>  	return 0;
>>  }
>> diff --git a/drivers/dax/hmem/hmem.c b/drivers/dax/hmem/hmem.c
>> index 5e7c53f18491..088f4060d4d5 100644
>> --- a/drivers/dax/hmem/hmem.c
>> +++ b/drivers/dax/hmem/hmem.c
>> @@ -9,6 +9,8 @@
>>  static bool region_idle;
>>  module_param_named(region_idle, region_idle, bool, 0644);
>>  
>> +static struct platform_device *dax_hmem_pdev;
> 
> I don't think you can assume there is only ever 1 hmem platform device.
> 
> hmat_register_target_devices() in particular iterates multiple memory
> regions and will create more than one.
> 
> What am I missing?

You may be correct that there can be more than one hmem platform device.
I was making this change based on a comment from Dan that it may not matter
which platform device these are created against.

I could be wrong in that assumption. If so we'll need to figure lout how to
determine which platform device a soft reserve resource would be created
against when they are added later in boot from a notification by the
srmem notification chain.

-Nathan

> Ira
> 
>> +
>>  static int dax_hmem_probe(struct platform_device *pdev)
>>  {
>>  	unsigned long flags = IORESOURCE_DAX_KMEM;
>> @@ -59,13 +61,13 @@ static void release_hmem(void *pdev)
>>  	platform_device_unregister(pdev);
>>  }
>>  
>> -static int hmem_register_device(struct device *host, int target_nid,
>> -				const struct resource *res)
>> +static int hmem_register_device(const struct resource *res)
>>  {
>> +	struct device *host = &dax_hmem_pdev->dev;
>>  	struct platform_device *pdev;
>>  	struct memregion_info info;
>> +	int target_nid, rc;
>>  	long id;
>> -	int rc;
>>  
>>  	if (IS_ENABLED(CONFIG_CXL_REGION) &&
>>  	    region_intersects(res->start, resource_size(res), IORESOURCE_MEM,
>> @@ -94,6 +96,7 @@ static int hmem_register_device(struct device *host, int target_nid,
>>  		return -ENOMEM;
>>  	}
>>  
>> +	target_nid = phys_to_target_node(res->start);
>>  	pdev->dev.numa_node = numa_map_to_online_node(target_nid);
>>  	info = (struct memregion_info) {
>>  		.target_node = target_nid,
>> @@ -125,7 +128,8 @@ static int hmem_register_device(struct device *host, int target_nid,
>>  
>>  static int dax_hmem_platform_probe(struct platform_device *pdev)
>>  {
>> -	return walk_hmem_resources(&pdev->dev, hmem_register_device);
>> +	dax_hmem_pdev = pdev;
>> +	return walk_hmem_resources(hmem_register_device);
>>  }
>>  
>>  static struct platform_driver dax_hmem_platform_driver = {
>> diff --git a/include/linux/dax.h b/include/linux/dax.h
>> index 9d3e3327af4c..beaa4bcb515c 100644
>> --- a/include/linux/dax.h
>> +++ b/include/linux/dax.h
>> @@ -276,14 +276,13 @@ static inline int dax_mem2blk_err(int err)
>>  }
>>  
>>  #ifdef CONFIG_DEV_DAX_HMEM_DEVICES
>> -void hmem_register_resource(int target_nid, struct resource *r);
>> +void hmem_register_resource(struct resource *r);
>>  #else
>> -static inline void hmem_register_resource(int target_nid, struct resource *r)
>> +static inline void hmem_register_resource(struct resource *r)
>>  {
>>  }
>>  #endif
>>  
>> -typedef int (*walk_hmem_fn)(struct device *dev, int target_nid,
>> -			    const struct resource *res);
>> -int walk_hmem_resources(struct device *dev, walk_hmem_fn fn);
>> +typedef int (*walk_hmem_fn)(const struct resource *res);
>> +int walk_hmem_resources(walk_hmem_fn fn);
>>  #endif
>> -- 
>> 2.43.0
>>
>>
> 
>