Re: [PATCH V6] ACPI:PRM: Reduce unnecessary printing to avoid the worries of regular users

[Rafael J. Wysocki]

On Fri, Jul 4, 2025 at 3:41 AM Zhu Qiyu <qiyuzhu2@xxxxxxx> wrote:
>
> Commit 088984c8d54c ("ACPI: PRM: Find EFI_MEMORY_RUNTIME block for PRM
> handler and context") introduces non-essential printing "Failed to find
> VA for GUID: xxxx, PA: 0x0" which causes unnecessary worry for regular
> users.
>
> Refer to PRM Spec Section 4.1.2[1], both static data buffer address
> and ACPI parameter buffer address may be NULL if they are not needed.
> So there is no need to print out "Failed to find VA ... " to intimidate
> regular users in that case.
>
> Link: https://uefi.org/sites/default/files/resources/Platform%20Runtime%20Mechanism%20-%20with%20legal%20notice.pdf # [1]
>
> Signed-off-by: Zhu Qiyu <qiyuzhu2@xxxxxxx>
> ---
> Previous versions can be found at:
> v1: https://lore.kernel.org/linux-acpi/20250427075317.42687-1-qiyuzhu2@xxxxxxx/
> v2: https://lore.kernel.org/linux-acpi/20250512010620.142155-1-qiyuzhu2@xxxxxxx/#r
> v3: https://lore.kernel.org/linux-acpi/20250512011833.142204-1-qiyuzhu2@xxxxxxx/t/#u
> v4: https://lore.kernel.org/linux-acpi/20250518062507.218855-1-qiyuzhu2@xxxxxxx/
> v5: https://lore.kernel.org/all/20250527024259.56996-1-qiyuzhu2@xxxxxxx/
>
> Changes in v2:
>  - Reduce the code changes.
> Changes in v3:
>  - Fixed title letters not showing.
> Changes in v4:
>  - Only print the necessary warnings.
> Changes in v5:
>  - Add more cases of print warnings.
> Changes in v6:
> -  Adjust the code comments.
>
>  drivers/acpi/prmt.c | 28 ++++++++++++++++++++++++++--
>  1 file changed, 26 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/acpi/prmt.c b/drivers/acpi/prmt.c
> index e549914a636c..d7857ca8fb4c 100644
> --- a/drivers/acpi/prmt.c
> +++ b/drivers/acpi/prmt.c
> @@ -85,8 +85,6 @@ static u64 efi_pa_va_lookup(efi_guid_t *guid, u64 pa)
>                 }
>         }
>
> -       pr_warn("Failed to find VA for GUID: %pUL, PA: 0x%llx", guid, pa);
> -
>         return 0;
>  }
>
> @@ -154,13 +152,39 @@ acpi_parse_prmt(union acpi_subtable_headers *header, const unsigned long end)
>                 guid_copy(&th->guid, (guid_t *)handler_info->handler_guid);
>                 th->handler_addr =
>                         (void *)efi_pa_va_lookup(&th->guid, handler_info->handler_address);
> +               /*
> +                * Print a warning message if handler_addr is zero which is not expected to
> +                * ever happen.
> +                */
> +               if (unlikely(!th->handler_addr))
> +                       pr_warn("Failed to find VA of handler for GUID: %pUL, PA: 0x%llx",
> +                               &th->guid, handler_info->handler_address);
>
>                 th->static_data_buffer_addr =
>                         efi_pa_va_lookup(&th->guid, handler_info->static_data_buffer_address);
> +               /*
> +                * According to the PRM specification, static_data_buffer_address can be zero,
> +                * so avoid printing a warning message in that case.
> +                * If the static_data_buffer_address passed to efi_pa_va_lookup() is nonzero
> +                * and the return value is zero, print a warning message in that case.
> +                */
> +               if (unlikely(!th->static_data_buffer_addr && handler_info->static_data_buffer_address))
> +                       pr_warn("Failed to find VA of static data buffer for GUID: %pUL, PA: 0x%llx",
> +                               &th->guid, handler_info->static_data_buffer_address);
>
>                 th->acpi_param_buffer_addr =
>                         efi_pa_va_lookup(&th->guid, handler_info->acpi_param_buffer_address);
>
> +               /*
> +                * According to the PRM specification, acpi_param_buffer_address can be zero,
> +                * so avoid printing a warning message in that case.
> +                * If the acpi_param_buffer_address passed to efi_pa_va_lookup() is nonzero and
> +                * the return value is zero, print a warning message in that case.
> +                */
> +               if (unlikely(!th->acpi_param_buffer_addr && handler_info->acpi_param_buffer_address))
> +                       pr_warn("Failed to find VA of acpi param buffer for GUID: %pUL, PA: 0x%llx",
> +                               &th->guid, handler_info->acpi_param_buffer_address);
> +
>         } while (++cur_handler < tm->handler_count && (handler_info = get_next_handler(handler_info)));
>
>         return 0;
>
> base-commit: a5806cd506af5a7c19bcd596e4708b5c464bfd21
> --

Applied as 6.17 material with some edits in the subject and changelog,
and in the new code comments added by the patch.

Thanks!