On Mon, 18 Nov 2019 at 12:45, Andy Shevchenko
<andriy.shevchenko@xxxxxxxxxxxxxxx> wrote:
>
> On Fri, Nov 15, 2019 at 04:28:10PM +0000, Ard Biesheuvel wrote:
> > On Fri, 15 Nov 2019 at 15:31, 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.
>
> > > +/*
> > > + * 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)
> > > +{
> > > + if (!fb_base || !fb_size)
> > > + return NULL;
> > > +
> >
> > 'return 0' please.
>
> Ah, sorry. Though I think we rather return -ENOVEV here.
>
fb_base and fb_size will only be set if earlycon=efifb is passed, so
this is not an error condition, and so returning an error is
incorrect.
> > I'll test this on actual arm64 hardware somewhere next week, and queue
> > it if it doesn't break anything (no need to resend for the above)
>
> Thanks!
>
Works fine for me
Tested-by: Ard Biesheuvel <ardb@xxxxxxxxxx> # arm64
> > > + if (pgprot_val(fb_prot) == pgprot_val(PAGE_KERNEL))
> > > + efi_fb = memremap(fb_base, fb_size, MEMREMAP_WB);
> > > + else
> > > + efi_fb = memremap(fb_base, fb_size, MEMREMAP_WC);
> > > +
> > > + return efi_fb ? 0 : -ENOMEM;
> > > +}
> > > +early_initcall(early_efi_map_fb);
>
> --
> With Best Regards,
> Andy Shevchenko
>
>
