linux-kernel - Re: [PATCH v2] mm: numa_memblks: introduce numa_add_reserved

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Message-ID: <20250403131617.000078fa@huawei.com>
Date: Thu, 3 Apr 2025 13:16:17 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Yuquan Wang <wangyuquan1236@...tium.com.cn>
CC: <dan.j.williams@...el.com>, <rppt@...nel.org>, <rafael@...nel.org>,
	<lenb@...nel.org>, <akpm@...ux-foundation.org>, <alison.schofield@...el.com>,
	<rrichter@....com>, <bfaccini@...dia.com>, <haibo1.xu@...el.com>,
	<david@...hat.com>, <linux-acpi@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
	<chenbaozi@...tium.com.cn>, <linux-cxl@...r.kernel.org>
Subject: Re: [PATCH v2] mm: numa_memblks: introduce numa_add_reserved_memblk

On Fri, 28 Mar 2025 17:21:32 +0800
Yuquan Wang <wangyuquan1236@...tium.com.cn> wrote:

> With numa_add_reserved_memblk(), kernel could add numa_memblk into
> numa_reserved_meminfo directly.
> 
> 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 suppot of future hotplug / CXL provisioning.
> 
> Signed-off-by: Yuquan Wang <wangyuquan1236@...tium.com.cn>

Given CFMWS is a CXL thing, +cc linux-cxl

Seems like a reasonable cleanup to me.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>


> ---
> 
> Changes in v2 (Thanks to Dan):
> - 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()
> - Provide a more explicit commit message
> 
>  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 00ac0d7bb8c9..70f1a7c6b54a 100644
> --- a/drivers/acpi/numa/srat.c
> +++ b/drivers/acpi/numa/srat.c
> @@ -458,7 +458,7 @@ 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