linux-kernel - Re: [PATCH] of: Fix memory block alignment in early_init_dt_add_memory

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Date:	Mon, 08 Sep 2014 14:55:04 +0100
From:	Grant Likely <grant.likely@...aro.org>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:	Geert Uytterhoeven <geert+renesas@...der.be>,
	Rob Herring <robh+dt@...nel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] of: Fix memory block alignment in
 early_init_dt_add_memory_arch()

On Wed, 27 Aug 2014 13:08:51 +0200, Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> Hi Grant,
> 
> On Wed, Aug 27, 2014 at 12:30 PM, Grant Likely <grant.likely@...aro.org> wrote:
> > On Wed, 20 Aug 2014 17:10:31 +0200, Geert Uytterhoeven <geert+renesas@...der.be> wrote:
> >> If a memory block is not aligned to PAGE_SIZE, its base address must be
> >> rounded up, not down, and its size must be reduced.
> >>
> >> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
> >
> > Looks reasonable. What is the situation that exposed this problem?
> 
> When ARM switched from arm_add_memory() to early_init_dt_add_memory_arch()
> for DT-based platforms, I just noticed this when comparing the two
> implementations.
> 
> I don't know if it triggers in the wild.
> 
> > Should size be checked for page alignment also?
> 
> Size is already rounded down if it's not page aligned, cfr. the context below.

Indeed it is. Silly me. Applied, thanks.

g.

> 
> >> ---
> >>  drivers/of/fdt.c | 6 +++++-
> >>  1 file changed, 5 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> >> index f46a24ffa3fe..95fa81b8ca19 100644
> >> --- a/drivers/of/fdt.c
> >> +++ b/drivers/of/fdt.c
> >> @@ -928,7 +928,11 @@ int __init early_init_dt_scan_chosen(unsigned long node, const char *uname,
> >>  void __init __weak early_init_dt_add_memory_arch(u64 base, u64 size)
> >>  {
> >>       const u64 phys_offset = __pa(PAGE_OFFSET);
> >> -     base &= PAGE_MASK;
> >> +
> >> +     if (!PAGE_ALIGNED(base)) {
> >> +             size -= PAGE_SIZE - (base & ~PAGE_MASK);
> >> +             base = PAGE_ALIGN(base);
> >> +     }
> >>       size &= PAGE_MASK;
> >>
> >>       if (base > MAX_PHYS_ADDR) {
> >> --
> >> 1.9.1
> 
> Gr{oetje,eeting}s,
> 
>                         Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds

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