linux-kernel - Re: [PATCH 1/1] ACPI: PRM: Skip the initialization when boot from legacy BIOS

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Message-ID: <CAJZ5v0httK0xmvA5zcYruU1Ypsw1YXHBOaPQxwCai8YDLsGkvA@mail.gmail.com>
Date: Mon, 27 Oct 2025 19:25:43 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: "Shang song (Lenovo)" <shangsong2@...mail.com>
Cc: "Rafael J . Wysocki" <rafael@...nel.org>, Len Brown <lenb@...nel.org>, linux-acpi@...r.kernel.org, 
	linux-kernel@...r.kernel.org, shangsong2@...ovo.com
Subject: Re: [PATCH 1/1] ACPI: PRM: Skip the initialization when boot from
 legacy BIOS

On Mon, Oct 13, 2025 at 10:38 AM Shang song (Lenovo)
<shangsong2@...mail.com> wrote:
>
> To address the confusion caused by the misleading "Failed to find VA for GUID..."
> message during legacy BIOS boot, making 'EFI_RUNTIME_SERVICES's earlier judgment
> can prevent this false alert.
>
> Signed-off-by: Shang song (Lenovo) <shangsong2@...mail.com>
> ---
>  drivers/acpi/prmt.c | 18 ++++++++----------
>  1 file changed, 8 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/acpi/prmt.c b/drivers/acpi/prmt.c
> index 6792d4385eee..ec367d322ab2 100644
> --- a/drivers/acpi/prmt.c
> +++ b/drivers/acpi/prmt.c
> @@ -305,11 +305,6 @@ static acpi_status acpi_platformrt_space_handler(u32 function,
>         efi_status_t status;
>         struct prm_context_buffer context;
>
> -       if (!efi_enabled(EFI_RUNTIME_SERVICES)) {
> -               pr_err_ratelimited("PRM: EFI runtime services no longer available\n");
> -               return AE_NO_HANDLER;
> -       }
> -

The check removed by this change addresses a different case than the
similar check in init_prmt(), so removing it when relocating the other
check is questionable.

Please limit this patch to the init_prmt() changes.

>         /*
>          * The returned acpi_status will always be AE_OK. Error values will be
>          * saved in the first byte of the PRM message buffer to be used by ASL.
> @@ -388,6 +383,14 @@ void __init init_prmt(void)
>         acpi_status status;
>         int mc;
>
> +       /*
> +        * Return immediately if EFI_RUNTIME_SERVICES is not enabled.
> +        */

One-line comment would be sufficient here.

> +       if (!efi_enabled(EFI_RUNTIME_SERVICES)) {
> +               pr_info("PRM: EFI runtime services unavailable, can not initialize.\n");
> +               return;
> +       }
> +
>         status = acpi_get_table(ACPI_SIG_PRMT, 0, &tbl);
>         if (ACPI_FAILURE(status))
>                 return;
> @@ -404,11 +407,6 @@ void __init init_prmt(void)
>
>         pr_info("PRM: found %u modules\n", mc);
>
> -       if (!efi_enabled(EFI_RUNTIME_SERVICES)) {
> -               pr_err("PRM: EFI runtime services unavailable\n");
> -               return;
> -       }
> -
>         status = acpi_install_address_space_handler(ACPI_ROOT_OBJECT,
>                                                     ACPI_ADR_SPACE_PLATFORM_RT,
>                                                     &acpi_platformrt_space_handler,
> --