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

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Message-ID: <09cb03e4-21f3-418c-98f2-66004cc3080f@siemens.com>
Date: Sun, 24 Aug 2025 08:47:42 +0200
From: Jan Kiszka <jan.kiszka@...mens.com>
To: Ard Biesheuvel <ardb@...nel.org>
Cc: Aaron Kling <webgeek1234@...il.com>, linux-efi@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] efistub: Lower default log level

On 24.08.25 02:31, Ard Biesheuvel wrote:
> On Sat, 16 Aug 2025 at 16:52, Jan Kiszka <jan.kiszka@...mens.com> wrote:
>>
>> 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.
>>
> 
> Hi Jan,
> 
> Is efi=debug too noisy for you?

Yes, also because it affects the kernel even more. I'm looking for
"efi=info".

I don't get the reason behind this change anymore as well. If you have a
splash screen shown, weren't you booting with "quiet" before already,
thus also without any stub messages?

Jan

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