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

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Message-ID: <CAMj1kXHyw3Oi=c3p+7q75vD4iJ+x642JzL7zHM4jpF4k937Uxg@mail.gmail.com>
Date: Mon, 25 Aug 2025 20:44:37 +1000
From: Ard Biesheuvel <ardb@...nel.org>
To: Jan Kiszka <jan.kiszka@...mens.com>
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 Sun, 24 Aug 2025 at 16:47, Jan Kiszka <jan.kiszka@...mens.com> wrote:
>
> 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?
>

Yeah, good point. IIRC that came up in the discussion but I can't
remember the motivation so it can't have been very convincing.

So should we just revert this change?