linux-kernel - Re: [PATCH 04/12] mips: Reserve memory for the kernel image resources

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Date:   Wed, 22 May 2019 16:54:23 +0300
From:   Serge Semin <fancer.lancer@...il.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Mike Rapoport <rppt@...ux.ibm.com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>,
        James Hogan <jhogan@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Bogendoerfer <tbogendoerfer@...e.de>,
        Huacai Chen <chenhc@...ote.com>,
        Stefan Agner <stefan@...er.ch>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Juergen Gross <jgross@...e.com>, linux-mips@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Atsushi Nemoto <anemo@....ocn.ne.jp>,
        "Maciej W. Rozycki" <macro@...ux-mips.org>
Subject: Re: [PATCH 04/12] mips: Reserve memory for the kernel image resources

On Wed, May 22, 2019 at 03:44:47PM +0200, Geert Uytterhoeven wrote:
> Hi Serge,
>
> ...
> 
> >
> > The problem might be fixed there by the next patch:
> > ---
> > diff --git a/arch/mips/dec/prom/memory.c b/arch/mips/dec/prom/memory.c
> > index 5073d2ed78bb..5a0c734b5d04 100644
> > --- a/arch/mips/dec/prom/memory.c
> > +++ b/arch/mips/dec/prom/memory.c
> > @@ -91,29 +91,14 @@ void __init prom_meminit(u32 magic)
> >                 pmax_setup_memory_region();
> >         else
> >                 rex_setup_memory_region();
> > -}
> > -
> > -void __init prom_free_prom_memory(void)
> > -{
> > -       unsigned long end;
> > -
> > -       /*
> > -        * Free everything below the kernel itself but leave
> > -        * the first page reserved for the exception handlers.
> > -        */
> >
> >  #if IS_ENABLED(CONFIG_DECLANCE)
> >         /*
> > -        * Leave 128 KB reserved for Lance memory for
> > -        * IOASIC DECstations.
> > +        * Reserve 128 KB for Lance memory for IOASIC DECstations.
> >          *
> >          * XXX: save this address for use in dec_lance.c?
> >          */
> >         if (IOASIC)
> > -               end = __pa(&_text) - 0x00020000;
> > -       else
> > +               memblock_reserve(__pa_symbol(&_text), 0x00020000);
> 
> Shouldn't that be
> 
>     memblock_reserve(__pa_symbol(&_text) - 0x00020000, 0x00020000);
> 
> ?
> 

Right. Thanks. The updated version of the patch is attached to this email.

-Sergey

> >  #endif
> > -               end = __pa(&_text);
> > -
> > -       free_init_pages("unused PROM memory", PAGE_SIZE, end);
> >  }
> > ---
> >
> > Didn't wanna use prom_FREE_prom_memory to actually reserve a memory
> > chunk, so I moved the reservation into the prom_meminit() method.
> 
> I guess Maciej will test this on real hardware, eventually...
> 
> > Regarding the first page for the exception handlers. We don't need
> > to reserve it here, since it is already done in arch/mips/kernel/traps.c .
> 
> Thanks for checking! That was actually something I was still wondering
> about...
> 
> 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

View attachment "fix_dec.patch" of type "text/x-patch" (953 bytes)