On Fri, 15 Nov 2019 at 12:37, Andy Shevchenko
<andriy.shevchenko@xxxxxxxxxxxxxxx> wrote:
>
> On Tue, Nov 12, 2019 at 06:12:40PM +0200, Andy Shevchenko 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 led 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.
>
> Please, hold on. I found an issue when no earlycon is not being provided in command line.
> I will fix, test and send a v3 soon.
>
Ok
> >
> > 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>
> > ---
> > v2:
> > - add __exitcall()
> > - swap type and attribute for __init / __exit functions as most used in the kernel
> > drivers/firmware/efi/earlycon.c | 34 +++++++++++++++++++++++++++++++++
> > 1 file changed, 34 insertions(+)
> >
> > diff --git a/drivers/firmware/efi/earlycon.c b/drivers/firmware/efi/earlycon.c
> > index c9a0efca17b0..8c6a3c67b7f2 100644
> > --- a/drivers/firmware/efi/earlycon.c
> > +++ b/drivers/firmware/efi/earlycon.c
> > @@ -17,14 +17,48 @@ 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 int __init 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 void __exit early_efi_unmap_fb(void)
> > +{
> > + memunmap(efi_fb);
> > +}
> > +__exitcall(early_efi_unmap_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
> >
>
> --
> With Best Regards,
> Andy Shevchenko
>
>
