On Wed, 30 Apr, at 10:13:03AM, Dave Young wrote:
>
> earlyprintk=efi,keep will cause kernel hangs while freeing initmem like below:
> [ 2.826089] VFS: Mounted root (ext4 filesystem) readonly on device 254:2.
> [ 2.846592] devtmpfs: mounted
> [ 2.856974] Freeing unused kernel memory: 880K (ffffffff817d4000 -
> ffffffff818b0000)
>
> It is caused by efi earlyprintk use __init function which will be freed later.
> Such as early_efi_write is marked as __init, also it will use early_ioremap
> which is init function as well.
>
> To fix this issue, I added one early initcall efi_ioremap_fb which will map
> the whole
> efi fb for later use. OTOH, adding a wrapper function efi_ioremap which will
> call
> early_ioremap before ioremap is available.
>
> With this patch applied efi boot ok with earlyprintk=efi,keep console=efi
>
> Signed-off-by: Dave Young <dyo...@redhat.com>
> ---
> arch/x86/platform/efi/early_printk.c | 54
> +++++++++++++++++++++++++++--------
> 1 file changed, 42 insertions(+), 12 deletions(-)
Thanks Dave, good catch. I've got a few comments below.
> +static __init int efi_ioremap_fb(void)
> +{
> + unsigned long base, size;
> +
> + base = boot_params.screen_info.lfb_base;
> + size = boot_params.screen_info.lfb_size;
> + efi_fb = ioremap(base, size);
> +
> + return efi_fb ? 0 : -ENOMEM;
> +}
> +early_initcall(efi_ioremap_fb);
So, here you're actually ioremap'ing the framebuffer irrespective of
whether anyone passed earlyprintk=efi,keep on the command line.
Furthermore, you'll perform the ioremap() even if some error was
encountered in early_efi_setup().
You need a way to figure out whether the ioremap() is actually needed.
Please document this function to explain why we need to ioremap() the
framebuffer from an early_initcall().
Oh and as a side note, please prefix functions in this file with
early_efi_*. Yeah, I realise that I suggested efi_ioremap() as a name -
my bad.
> +static __init_refok void *efi_ioremap(unsigned long start, unsigned long len)
> +{
> + unsigned long base;
> +
> + base = boot_params.screen_info.lfb_base;
> + if (efi_fb)
> + return (efi_fb + start - base);
> + else
> + return early_ioremap(start, len);
> +}
Adding .lfb_base in the caller and then subtracting here seems
needlessly complicated. Instead I'd suggest making early_efi_map() take
an offset and a length, and document when each framebuffer is used.
--
Matt Fleming, Intel Open Source Technology Center
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