On Mon, 11 Nov 2019 at 15:44, Andy Shevchenko
<andriy.shevchenko@xxxxxxxxxxxxxxx> wrote:
>
> When the commit 69c1f396f25b ("efi/x86: Convert x86 EFI earlyprintk
> into generic earlycon implementation") moved x86 specific EFI earlyprintk
> implementation to shared location it also tweaked the behaviour. In particular
> it dropped a trick with full framebuffer remapping after page initialization.
> This lead to two regressions:
> 1) very slow scrolling after page initialization;
> 2) kernel hang when keep_bootcon parameter is being provided.
>
> Returning the trick back fixes #2 and mitigates, i.e. reduces the window when
> slowness appears, #1 presumably due to eliminating heavy map()/unmap()
> operations per each pixel line on the screen.
>
> Fixes: 69c1f396f25b ("efi/x86: Convert x86 EFI earlyprintk into generic earlycon implementation")
> Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> Cc: Alexander Graf <agraf@xxxxxxx>
> Cc: Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Hi Andy,
Thanks for fixing this. One question below.
> ---
> drivers/firmware/efi/earlycon.c | 33 +++++++++++++++++++++++++++++++++
> 1 file changed, 33 insertions(+)
>
> diff --git a/drivers/firmware/efi/earlycon.c b/drivers/firmware/efi/earlycon.c
> index c9a0efca17b0..ddb6c0ff2553 100644
> --- a/drivers/firmware/efi/earlycon.c
> +++ b/drivers/firmware/efi/earlycon.c
> @@ -17,14 +17,47 @@ static const struct font_desc *font;
> static u32 efi_x, efi_y;
> static u64 fb_base;
> static pgprot_t fb_prot;
> +static void *efi_fb;
> +
> +/*
> + * efi earlycon needs to use early_memremap() to map the framebuffer.
> + * But early_memremap() is not usable for 'earlycon=efifb keep_bootcon',
> + * memremap() should be used instead. memremap() will be available after
> + * paging_init() which is earlier than initcall callbacks. Thus adding this
> + * early initcall function early_efi_map_fb() to map the whole efi framebuffer.
> + */
> +static __init int early_efi_map_fb(void)
> +{
> + u32 size;
> +
> + size = screen_info.lfb_size;
> + if (pgprot_val(fb_prot) == pgprot_val(PAGE_KERNEL))
> + efi_fb = memremap(fb_base, size, MEMREMAP_WB);
> + else
> + efi_fb = memremap(fb_base, size, MEMREMAP_WC);
> +
> + return efi_fb ? 0 : -ENOMEM;
> +}
> +early_initcall(early_efi_map_fb);
> +
> +static __exit void early_efi_unmap_fb(void)
Will there be a user for this routine? If not, can we just drop it?
> +{
> + memunmap(efi_fb);
> +}
>
> static __ref void *efi_earlycon_map(unsigned long start, unsigned long len)
> {
> + if (efi_fb)
> + return efi_fb + start;
> +
> return early_memremap_prot(fb_base + start, len, pgprot_val(fb_prot));
> }
>
> static __ref void efi_earlycon_unmap(void *addr, unsigned long len)
> {
> + if (efi_fb)
> + return;
> +
> early_memunmap(addr, len);
> }
>
> --
> 2.24.0.rc1
>
