Re: [PATCH v3 1/4] kernel/resource: Provide mem region release for SOFT RESERVES

[Jonathan Cameron]

On Thu, 3 Apr 2025 13:33:12 -0500
Terry Bowman <terry.bowman@xxxxxxx> wrote:

> From: Nathan Fontenot <nathan.fontenot@xxxxxxx>
> 
> Add a release_Sam_region_adjustable() interface to allow for

Who is Sam?  (typo)

> removing SOFT RESERVE memory resources. This extracts out the code
> to remove a mem region into a common __release_mem_region_adjustable()
> routine, this routine takes additional parameters of an IORES
> descriptor type to add checks for IORES_DESC_* and a flag to check
> for IORESOURCE_BUSY to control it's behavior.
> 
> The existing release_mem_region_adjustable() is a front end to the
> common code and a new release_srmem_region_adjustable() is added to
> release SOFT RESERVE resources.
> 
> Signed-off-by: Nathan Fontenot <nathan.fontenot@xxxxxxx>
> Signed-off-by: Terry Bowman <terry.bowman@xxxxxxx>
> ---
>  include/linux/ioport.h |  3 +++
>  kernel/resource.c      | 55 +++++++++++++++++++++++++++++++++++++++---
>  2 files changed, 54 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/ioport.h b/include/linux/ioport.h
> index 5385349f0b8a..718360c9c724 100644
> --- a/include/linux/ioport.h
> +++ b/include/linux/ioport.h
> @@ -357,6 +357,9 @@ extern void __release_region(struct resource *, resource_size_t,
>  #ifdef CONFIG_MEMORY_HOTREMOVE
>  extern void release_mem_region_adjustable(resource_size_t, resource_size_t);
>  #endif
> +#ifdef CONFIG_CXL_REGION
> +extern void release_srmem_region_adjustable(resource_size_t, resource_size_t);
I'm not sure the srmem is obvious enough.  Maybe it's worth the long
name to spell it out some more.. e.g. something like

extern void release_softresv_mem_region_adjustable() ?
> +#endif
>  #ifdef CONFIG_MEMORY_HOTPLUG
>  extern void merge_system_ram_resource(struct resource *res);
>  #endif
> diff --git a/kernel/resource.c b/kernel/resource.c
> index 12004452d999..0195b31064b0 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -1387,7 +1387,7 @@ void __release_region(struct resource *parent, resource_size_t start,
>  }
>  EXPORT_SYMBOL(__release_region);
>  
> -#ifdef CONFIG_MEMORY_HOTREMOVE
> +#if defined(CONFIG_MEMORY_HOTREMOVE) || defined(CONFIG_CXL_REGION)
>  /**
>   * release_mem_region_adjustable - release a previously reserved memory region

Looks like you left the old docs which I'm guessing is not the intent.

>   * @start: resource start address
> @@ -1407,7 +1407,10 @@ 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_mem_region_adjustable(resource_size_t start,
> +					    resource_size_t size,
> +					    bool busy_check,
> +					    int res_desc)
>  {
>  	struct resource *parent = &iomem_resource;
>  	struct resource *new_res = NULL;
> @@ -1446,7 +1449,12 @@ 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;
> +		}
> +
> +		if (res_desc != IORES_DESC_NONE && res->desc != res_desc) {
>  			p = &res->child;
>  			continue;
>  		}
> @@ -1496,7 +1504,46 @@ void release_mem_region_adjustable(resource_size_t start, resource_size_t size)
>  	write_unlock(&resource_lock);
>  	free_resource(new_res);
>  }
> -#endif	/* CONFIG_MEMORY_HOTREMOVE */
> +#endif
> +
> +#ifdef CONFIG_MEMORY_HOTREMOVE
> +/**
> + * release_mem_region_adjustable - release a previously reserved memory region
As above. I was surprised to see new docs in here for an existing function.
I think you forgot to delete the now wrongly placed ones above.

Jonathan