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

["Rafael J. Wysocki" <rafael@kernel.org>]

On Mon, Jan 13, 2025 at 6:44 PM Gregory Price <gourry@gourry.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@intel.com>
> Signed-off-by: Gregory Price <gourry@gourry.net>
> Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> Acked-by: David Hildenbrand <david@redhat.com>
> Acked-by: Dan Williams <dan.j.williams@intel.com>
> Tested-by: Fan Ni <fan.ni@samsung.com>

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.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
>