Re: [PATCH v2 1/4] kernel/resource: Introduce managed SOFT RESERVED resources

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

On 1/21/2025 11:52 PM, Fan Ni wrote:
> On Thu, Jan 16, 2025 at 11:42:05AM -0600, Nathan Fontenot wrote:
>> Introduce the ability to manage SOFT RESERVED kernel resources prior to
>> these resources being  placed in the iomem resource tree. This provides
>> the ability for drivers to update SOFT RESERVED resources that intersect
>> with their memory resources.
>>
>> During boot, any resources marked as IORES_DESC_SOFT_RESERVED are placed
>> on the soft reserve resource tree. Once boot completes all resources
>> are placed on the iomem resource tree. This behavior is gated by a new
>> kernel option CONFIG_SOFT_RESERVED_MANAGED.
>>
>> As part of this update two new interfaces are added for management of
>> the SOFT RESERVED resources. The release_srmem_region_adjustable()
>> routine allows for removing pieces of SOFT RESERVED resources. The
>> the merge_srmem_resources() allows drivers to merge any remaining SOFT
>> RESERVED resources into the iomem resource tree once updatea are complete.
>>
>> Signed-off-by: Nathan Fontenot <nathan.fontenot@amd.com>
>> ---
>>  include/linux/ioport.h |  9 +++++
>>  kernel/resource.c      | 79 +++++++++++++++++++++++++++++++++++++++---
>>  lib/Kconfig            |  4 +++
>>  3 files changed, 87 insertions(+), 5 deletions(-)
>>
>> diff --git a/include/linux/ioport.h b/include/linux/ioport.h
>> index 6e9fb667a1c5..2c95cf0be45e 100644
>> --- a/include/linux/ioport.h
>> +++ b/include/linux/ioport.h
>> @@ -249,6 +249,15 @@ struct resource *lookup_resource(struct resource *root, resource_size_t start);
>>  int adjust_resource(struct resource *res, resource_size_t start,
>>  		    resource_size_t size);
>>  resource_size_t resource_alignment(struct resource *res);
>> +
>> +#ifdef CONFIG_SOFT_RESERVED_MANAGED
>> +void merge_srmem_resources(void);
>> +extern void release_srmem_region_adjustable(resource_size_t start,
>> +					    resource_size_t size);
>> +#else
>> +static inline void merge_srmem_resources(void) { }
>> +#endif
>> +
>>  static inline resource_size_t resource_size(const struct resource *res)
>>  {
>>  	return res->end - res->start + 1;
>> diff --git a/kernel/resource.c b/kernel/resource.c
>> index a83040fde236..9db420078a3f 100644
>> --- a/kernel/resource.c
>> +++ b/kernel/resource.c
>> @@ -48,6 +48,14 @@ struct resource iomem_resource = {
>>  };
>>  EXPORT_SYMBOL(iomem_resource);
>>  
>> +static struct resource srmem_resource = {
>> +	.name	= "Soft Reserved mem",
>> +	.start	= 0,
>> +	.end	= -1,
>> +	.flags	= IORESOURCE_MEM,
>> +	.desc	= IORES_DESC_SOFT_RESERVED,
>> +};
>> +
>>  static DEFINE_RWLOCK(resource_lock);
>>  
>>  static struct resource *next_resource(struct resource *p, bool skip_children)
>> @@ -818,6 +826,19 @@ static struct resource * __insert_resource(struct resource *parent, struct resou
>>  {
>>  	struct resource *first, *next;
>>  
>> +	if (IS_ENABLED(CONFIG_SOFT_RESERVED_MANAGED)) {
>> +		/*
>> +		 * During boot SOFT RESERVED resources are placed on the srmem
>> +		 * resource tree. These resources may be updated later in boot,
>> +		 * for example see the CXL driver, prior to being merged into
>> +		 * the iomem resource tree.
>> +		 */
>> +		if (system_state < SYSTEM_RUNNING &&
>> +		    parent == &iomem_resource &&
>> +		    new->desc == IORES_DESC_SOFT_RESERVED)
>> +			parent = &srmem_resource;
>> +	}
>> +
>>  	for (;; parent = first) {
>>  		first = __request_resource(parent, new);
>>  		if (!first)
>> @@ -1336,11 +1357,12 @@ void __release_region(struct resource *parent, resource_size_t start,
>>  }
>>  EXPORT_SYMBOL(__release_region);
>>  
>> -#ifdef CONFIG_MEMORY_HOTREMOVE
> 
> If CONFIG_MEMORY_HOTREMOVE not defined, it seems we do not have a
> user for release_region_adjustable as
> release_mem_region_adjustable() will not exist.

The release_region_adjustable() routine is used by by release_mem_region_adjustable()
and release_srmem_region_adjustable(). We could put the following around
release_region_adjustable() to prevent it being present when not used.

#if defined(CONFIG_MEMORY_HOTREMOVE) || defined(CONFIG_SOFT_RESERVED_MANAGED)

-Nathan

> 
> Fan
>>  /**
>> - * release_mem_region_adjustable - release a previously reserved memory region
>> + * release_region_adjustable - release a previously reserved memory region
>> + * @parent: resource tree to release resource from
>>   * @start: resource start address
>>   * @size: resource region size
>> + * @busy_check: check for IORESOURCE_BUSY
>>   *
>>   * This interface is intended for memory hot-delete.  The requested region
>>   * is released from a currently busy memory resource.  The requested region
>> @@ -1356,9 +1378,11 @@ EXPORT_SYMBOL(__release_region);
>>   *   assumes that all children remain in the lower address entry for
>>   *   simplicity.  Enhance this logic when necessary.
>>   */
>> -void release_mem_region_adjustable(resource_size_t start, resource_size_t size)
>> +static void release_region_adjustable(struct resource *parent,
>> +				      resource_size_t start,
>> +				      resource_size_t size,
>> +				      bool busy_check)
>>  {
>> -	struct resource *parent = &iomem_resource;
>>  	struct resource *new_res = NULL;
>>  	bool alloc_nofail = false;
>>  	struct resource **p;
>> @@ -1395,7 +1419,7 @@ void release_mem_region_adjustable(resource_size_t start, resource_size_t size)
>>  		if (!(res->flags & IORESOURCE_MEM))
>>  			break;
>>  
>> -		if (!(res->flags & IORESOURCE_BUSY)) {
>> +		if (busy_check && !(res->flags & IORESOURCE_BUSY)) {
>>  			p = &res->child;
>>  			continue;
>>  		}
>> @@ -1445,6 +1469,51 @@ void release_mem_region_adjustable(resource_size_t start, resource_size_t size)
>>  	write_unlock(&resource_lock);
>>  	free_resource(new_res);
>>  }
>> +
>> +#ifdef CONFIG_SOFT_RESERVED_MANAGED
>> +/**
>> + * merge_srmem_resources - merge srmem resources into the iomem resource tree
>> + *
>> + * This is intended to allow kernel drivers that manage the SOFT RESERVED
>> + * resources to merge any remaining resources into the iomem resource tree
>> + * once any updates have been made.
>> + */
>> +void merge_srmem_resources(void)
>> +{
>> +	struct resource *res, *next;
>> +	int rc;
>> +
>> +	for (res = srmem_resource.child; res; res = next) {
>> +		next = next_resource(res, true);
>> +
>> +		write_lock(&resource_lock);
>> +
>> +		if (WARN_ON(__release_resource(res, true))) {
>> +			write_unlock(&resource_lock);
>> +			continue;
>> +		}
>> +
>> +		if (WARN_ON(__insert_resource(&iomem_resource, res)))
>> +			__insert_resource(&srmem_resource, res);
>> +
>> +		write_unlock(&resource_lock);
>> +	}
>> +}
>> +EXPORT_SYMBOL_GPL(merge_srmem_resources);
>> +
>> +void release_srmem_region_adjustable(resource_size_t start,
>> +				     resource_size_t size)
>> +{
>> +	release_region_adjustable(&srmem_resource, start, size, false);
>> +}
>> +EXPORT_SYMBOL(release_srmem_region_adjustable);
>> +#endif
>> +
>> +#ifdef CONFIG_MEMORY_HOTREMOVE
>> +void release_mem_region_adjustable(resource_size_t start, resource_size_t size)
>> +{
>> +	release_region_adjustable(&iomem_resource, start, size, true);
>> +}
>>  #endif	/* CONFIG_MEMORY_HOTREMOVE */
>>  
>>  #ifdef CONFIG_MEMORY_HOTPLUG
>> diff --git a/lib/Kconfig b/lib/Kconfig
>> index b38849af6f13..4f4011334051 100644
>> --- a/lib/Kconfig
>> +++ b/lib/Kconfig
>> @@ -777,3 +777,7 @@ config POLYNOMIAL
>>  
>>  config FIRMWARE_TABLE
>>  	bool
>> +
>> +config SOFT_RESERVED_MANAGED
>> +	bool
>> +	default n
>> -- 
>> 2.43.0
>>