linux-kernel - Re: [RESEND v7 3/3] acpi,srat: give memory block size advice based on CFMWS alignment

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Message-ID: <67857eaa6e284_1863f329487@iweiny-mobl.notmuch>
Date: Mon, 13 Jan 2025 14:59:22 -0600
From: Ira Weiny <ira.weiny@...el.com>
To: Gregory Price <gourry@...rry.net>, <linux-mm@...ck.org>,
	<linux-acpi@...r.kernel.org>
CC: <kernel-team@...a.com>, <x86@...nel.org>, <linux-kernel@...r.kernel.org>,
	<dave.hansen@...ux.intel.com>, <luto@...nel.org>, <peterz@...radead.org>,
	<tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>, <hpa@...or.com>,
	<rafael@...nel.org>, <lenb@...nel.org>, <david@...hat.com>,
	<osalvador@...e.de>, <gregkh@...uxfoundation.org>,
	<akpm@...ux-foundation.org>, <dan.j.williams@...el.com>,
	<Jonathan.Cameron@...wei.com>, <alison.schofield@...el.com>,
	<rrichter@....com>, <rppt@...nel.org>, <gourry@...rry.net>,
	<bfaccini@...dia.com>, <haibo1.xu@...el.com>, <dave.jiang@...el.com>, Fan Ni
	<fan.ni@...sung.com>
Subject: Re: [RESEND v7 3/3] acpi,srat: give memory block size advice based
 on CFMWS alignment

Gregory Price wrote:
> Capacity is stranded when CFMWS regions are not aligned to block size.
> On x86, block size increases with capacity (2G blocks @ 64G capacity).
> 
> Use CFMWS base/size to report memory block size alignment advice.
> 
> Suggested-by: Dan Williams <dan.j.williams@...el.com>
> Signed-off-by: Gregory Price <gourry@...rry.net>
> Acked-by: Mike Rapoport (Microsoft) <rppt@...nel.org>
> Acked-by: David Hildenbrand <david@...hat.com>
> Acked-by: Dan Williams <dan.j.williams@...el.com>
> Tested-by: Fan Ni <fan.ni@...sung.com>
> ---
>  drivers/acpi/numa/srat.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/acpi/numa/srat.c b/drivers/acpi/numa/srat.c
> index 59fffe34c9d0..7526119fe945 100644
> --- a/drivers/acpi/numa/srat.c
> +++ b/drivers/acpi/numa/srat.c
> @@ -14,6 +14,7 @@
>  #include <linux/errno.h>
>  #include <linux/acpi.h>
>  #include <linux/memblock.h>
> +#include <linux/memory.h>
>  #include <linux/numa.h>
>  #include <linux/nodemask.h>
>  #include <linux/topology.h>
> @@ -425,13 +426,22 @@ static int __init acpi_parse_cfmws(union acpi_subtable_headers *header,
>  {
>  	struct acpi_cedt_cfmws *cfmws;
>  	int *fake_pxm = arg;
> -	u64 start, end;
> +	u64 start, end, align;
>  	int node;
>  
>  	cfmws = (struct acpi_cedt_cfmws *)header;
>  	start = cfmws->base_hpa;
>  	end = cfmws->base_hpa + cfmws->window_size;
>  
> +	/* Align memblock size to CFMW regions if possible */
> +	align = 1UL << __ffs(start | end);
> +	if (align >= SZ_256M) {
> +		if (memory_block_advise_max_size(align) < 0)
> +			pr_warn("CFMWS: memblock size advise failed\n");

I wonder if it would be good to print the return value here so the user
knows why this failed?

But either way.

Reviewed-by: Ira Weiny <ira.weiny@...el.com>

> +	} else {
> +		pr_err("CFMWS: [BIOS BUG] base/size alignment violates spec\n");
> +	}
> +
>  	/*
>  	 * The SRAT may have already described NUMA details for all,
>  	 * or a portion of, this CFMWS HPA range. Extend the memblks
> -- 
> 2.47.1
> 
>