linux-kernel - Re: [PATCH] efistub: Lower default log level

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Message-ID: <45692a2c-ba3d-45a2-9ab1-cf6982dbf788@siemens.com>
Date: Sat, 16 Aug 2025 08:52:02 +0200
From: Jan Kiszka <jan.kiszka@...mens.com>
To: Ard Biesheuvel <ardb@...nel.org>, Aaron Kling <webgeek1234@...il.com>
Cc: linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] efistub: Lower default log level

On 15.07.25 03:35, Ard Biesheuvel wrote:
> On Tue, 8 Jul 2025 at 17:31, Aaron Kling <webgeek1234@...il.com> wrote:
>>
>> On Tue, Jul 8, 2025 at 2:30 AM Aaron Kling via B4 Relay
>> <devnull+webgeek1234.gmail.com@...nel.org> wrote:
>>>
>>> From: Aaron Kling <webgeek1234@...il.com>
>>>
>>> Some uefi implementations will write the efistub logs to the display
>>> over a splash image. This is not desirable for debug and info logs, so
>>> lower the default efi log level to exclude them.
>>>
>>> Suggested-by: Ard Biesheuvel <ardb@...nel.org>
>>> Signed-off-by: Aaron Kling <webgeek1234@...il.com>
>>> ---
>>>  drivers/firmware/efi/libstub/printk.c | 4 ++--
>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/firmware/efi/libstub/printk.c b/drivers/firmware/efi/libstub/printk.c
>>> index 3a67a2cea7bdf1aa215d48dbf9ece4ceec6e4c28..bc599212c05dd746a9c54abbbe61a4bf70f1a8c4 100644
>>> --- a/drivers/firmware/efi/libstub/printk.c
>>> +++ b/drivers/firmware/efi/libstub/printk.c
>>> @@ -5,13 +5,13 @@
>>>  #include <linux/ctype.h>
>>>  #include <linux/efi.h>
>>>  #include <linux/kernel.h>
>>> -#include <linux/printk.h> /* For CONSOLE_LOGLEVEL_* */
>>> +#include <linux/kern_levels.h>
>>>  #include <asm/efi.h>
>>>  #include <asm/setup.h>
>>>
>>>  #include "efistub.h"
>>>
>>> -int efi_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
>>> +int efi_loglevel = LOGLEVEL_NOTICE;
>>>
>>>  /**
>>>   * efi_char16_puts() - Write a UCS-2 encoded string to the console
>>>
>>> ---
>>> base-commit: d7b8f8e20813f0179d8ef519541a3527e7661d3a
>>> change-id: 20250708-efi-default-loglevel-4da5a36cac87
>>>
>>> Best regards,
>>> --
>>> Aaron Kling <webgeek1234@...il.com>
>>
>> This patch was originally suggested a few months ago [0], but as far
>> as I can tell was never queued for merge. Since I'm also hitting a
>> case where this is relevant, I'm sending this in to bring attention
>> back to it.
>>
> 
> I've queued this up now - thanks.
> 

And how can I get back the loglevel info? It seems I can only choose
between notice, silent and debug now. And the latter two only by also
touching the kernel's loglevel.

I'm particularly missing [1] in my UART logs now which is helpful in
understanding this essential system state.

Jan

[1]
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/firmware/efi/libstub/secureboot.c?id=dfd4b508c8c6106083698a0dd5e35aecc7c48725#n60

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