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

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Message-ID: <CAJZ5v0gU-VF_wDYP-WLxt3MsT4WqXQZStCwB4YkBphqQrS6y1w@mail.gmail.com>
Date: Mon, 13 Jan 2025 20:10:24 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: gourry@...rry.net
Cc: linux-mm@...ck.org, linux-acpi@...r.kernel.org, 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, 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

On Mon, Jan 13, 2025 at 6:44 PM Gregory Price <gourry@...rry.net> 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>

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.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");
> +       } 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
>