[v2] mm: numa_memblks: introduce numa_add_reserved_memblk

acpi_parse_cfmws() currently adds empty CFMWS ranges to numa_meminfo
with the expectation that numa_cleanup_meminfo moves them to
numa_reserved_meminfo. There is no need for that indirection when it is
known in advance that these unpopulated ranges are meant for
numa_reserved_meminfo in support of future hotplug / CXL provisioning.

Introduce and use numa_add_reserved_memblk() to add the empty CFMWS
ranges directly.

Signed-off-by: Yuquan Wang <wangyuquan1236@phytium.com.cn>
---

Changes in v2 (Thanks to Dan & Alison):
- Use numa_add_reserved_memblk() to replace numa_add_memblk() in acpi_parse_cfmws()
- Add comments to describe the usage of numa_add_reserved_memblk()
- Updating the commit message to clarify the purpose of the patch

 drivers/acpi/numa/srat.c     |  2 +-
 include/linux/numa_memblks.h |  1 +
 mm/numa_memblks.c            | 22 ++++++++++++++++++++++
 3 files changed, 24 insertions(+), 1 deletion(-)

On Wed, Apr 09, 2025 at 12:01:21PM +0800, Yuquan Wang wrote:
> acpi_parse_cfmws() currently adds empty CFMWS ranges to numa_meminfo
> with the expectation that numa_cleanup_meminfo moves them to
> numa_reserved_meminfo. There is no need for that indirection when it is
> known in advance that these unpopulated ranges are meant for
> numa_reserved_meminfo in support of future hotplug / CXL provisioning.
> 
> Introduce and use numa_add_reserved_memblk() to add the empty CFMWS
> ranges directly.
> 
> Signed-off-by: Yuquan Wang <wangyuquan1236@phytium.com.cn>

Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

> ---
> 
> Changes in v2 (Thanks to Dan & Alison):
> - Use numa_add_reserved_memblk() to replace numa_add_memblk() in acpi_parse_cfmws()
> - Add comments to describe the usage of numa_add_reserved_memblk()
> - Updating the commit message to clarify the purpose of the patch
> 
>  drivers/acpi/numa/srat.c     |  2 +-
>  include/linux/numa_memblks.h |  1 +
>  mm/numa_memblks.c            | 22 ++++++++++++++++++++++
>  3 files changed, 24 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/acpi/numa/srat.c b/drivers/acpi/numa/srat.c
> index 0a725e46d017..751774f0b4e5 100644
> --- a/drivers/acpi/numa/srat.c
> +++ b/drivers/acpi/numa/srat.c
> @@ -453,7 +453,7 @@ static int __init acpi_parse_cfmws(union acpi_subtable_headers *header,
>  		return -EINVAL;
>  	}
>  
> -	if (numa_add_memblk(node, start, end) < 0) {
> +	if (numa_add_reserved_memblk(node, start, end) < 0) {
>  		/* CXL driver must handle the NUMA_NO_NODE case */
>  		pr_warn("ACPI NUMA: Failed to add memblk for CFMWS node %d [mem %#llx-%#llx]\n",
>  			node, start, end);
> diff --git a/include/linux/numa_memblks.h b/include/linux/numa_memblks.h
> index dd85613cdd86..991076cba7c5 100644
> --- a/include/linux/numa_memblks.h
> +++ b/include/linux/numa_memblks.h
> @@ -22,6 +22,7 @@ struct numa_meminfo {
>  };
>  
>  int __init numa_add_memblk(int nodeid, u64 start, u64 end);
> +int __init numa_add_reserved_memblk(int nid, u64 start, u64 end);
>  void __init numa_remove_memblk_from(int idx, struct numa_meminfo *mi);
>  
>  int __init numa_cleanup_meminfo(struct numa_meminfo *mi);
> diff --git a/mm/numa_memblks.c b/mm/numa_memblks.c
> index ff4054f4334d..541a99c4071a 100644
> --- a/mm/numa_memblks.c
> +++ b/mm/numa_memblks.c
> @@ -200,6 +200,28 @@ int __init numa_add_memblk(int nid, u64 start, u64 end)
>  	return numa_add_memblk_to(nid, start, end, &numa_meminfo);
>  }
>  
> +/**
> + * numa_add_reserved_memblk - Add one numa_memblk to numa_reserved_meminfo
> + * @nid: NUMA node ID of the new memblk
> + * @start: Start address of the new memblk
> + * @end: End address of the new memblk
> + *
> + * Add a new memblk to the numa_reserved_meminfo.
> + *
> + * Usage Case: numa_cleanup_meminfo() reconciles all numa_memblk instances
> + * against memblock_type information and moves any that intersect reserved
> + * ranges to numa_reserved_meminfo. However, when that information is known
> + * ahead of time, we use numa_add_reserved_memblk() to add the numa_memblk
> + * to numa_reserved_meminfo directly.
> + *
> + * RETURNS:
> + * 0 on success, -errno on failure.
> + */
> +int __init numa_add_reserved_memblk(int nid, u64 start, u64 end)
> +{
> +	return numa_add_memblk_to(nid, start, end, &numa_reserved_meminfo);
> +}
> +
>  /**
>   * numa_cleanup_meminfo - Cleanup a numa_meminfo
>   * @mi: numa_meminfo to clean up
> -- 
> 2.34.1
> 
>