linux-kernel - Re: [PATCH] efi: Downgrade "EFI_MEMMAP is not enabled" message

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Date:   Fri, 1 Mar 2019 14:53:39 +0100
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     "Lee, Chun-Yi" <jlee@...e.com>,
        linux-efi <linux-efi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] efi: Downgrade "EFI_MEMMAP is not enabled" message

On Fri, 1 Mar 2019 at 14:40, Takashi Iwai <tiwai@...e.de> wrote:
>
> Since 38ac0287b7f4 ("fbdev/efifb: Honour UEFI memory map attributes
> when mapping the FB"), efifb_probe() checks its memory range via
> efi_mem_desc_lookup(), and this leads to a spurious error message
> "EFI_MEMMAP is not enabled" at every boot on KVM.  This is quite
> annoying since the error message appears even if you set "quiet" boot
> option.
>
> Actually there are only a few places that call efi_mem_desc_lookup()
> function, and the other callers do give the explicit error messages
> when the function returns an error in anyway.  That is, the error
> message in the function is more or less moot.
>
> So let's downgrade the error message for stop annoying users.
>
> Fixes: 38ac0287b7f4 ("fbdev/efifb: Honour UEFI memory map attributes when mapping the FB")
> Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1127339
> Signed-off-by: Takashi Iwai <tiwai@...e.de>
> ---
>  drivers/firmware/efi/efi.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
> index 55b77c576c42..50ac33097458 100644
> --- a/drivers/firmware/efi/efi.c
> +++ b/drivers/firmware/efi/efi.c
> @@ -409,7 +409,7 @@ int efi_mem_desc_lookup(u64 phys_addr, efi_memory_desc_t *out_md)
>         efi_memory_desc_t *md;
>
>         if (!efi_enabled(EFI_MEMMAP)) {
> -               pr_err_once("EFI_MEMMAP is not enabled.\n");
> +               pr_debug("EFI_MEMMAP is not enabled.\n");
>                 return -EINVAL;
>         }
>

efifb_probe() only calls efi_mem_desc_lookup() if
screen_info.orig_video_isVGA == VIDEO_TYPE_EFI, which only gets
assigned on a EFI boot.

So even though I don't object to the patch as is, I would like to
understand where this error message is coming from, given that it
means that you are running on a UEFI system without the EFI memory
map.

Is this system booting via GRUB in EFI mode?