[PATCH v2] efi/earlycon: Remap entire framebuffer after page initialization

[PATCH v2] efi/earlycon: Remap entire framebuffer after page initialization

[Andy Shevchenko]

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.

Fixes: 69c1f396f25b ("efi/x86: Convert x86 EFI earlyprintk into generic earlycon implementation")
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Alexander Graf <agraf@suse.de>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
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

Re: [PATCH v2] efi/earlycon: Remap entire framebuffer after page initialization

[Andy Shevchenko]

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.

> 
> Fixes: 69c1f396f25b ("efi/x86: Convert x86 EFI earlyprintk into generic earlycon implementation")
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Alexander Graf <agraf@suse.de>
> Cc: Matt Fleming <matt@codeblueprint.co.uk>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
> 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

Re: [PATCH v2] efi/earlycon: Remap entire framebuffer after page initialization

[Ard Biesheuvel]

On Fri, 15 Nov 2019 at 12:37, Andy Shevchenko
<andriy.shevchenko@linux.intel.com> 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@linaro.org>
> > Cc: Alexander Graf <agraf@suse.de>
> > Cc: Matt Fleming <matt@codeblueprint.co.uk>
> > Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> > ---
> > 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
>
>