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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Mon, 11 May 2020 17:24:30 +0200
Message-ID: <CAMuHMdW1S91i3x0unNcJnypHse7ifynGb4dZcVhJaemR3GH1Pg@mail.gmail.com>
Subject: Re: [PATCH 31/31] module: move the set_fs hack for flush_icache_range
 to m68k
To:     Christoph Hellwig <hch@lst.de>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Roman Zippel <zippel@linux-m68k.org>,
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Hi Christoph,

On Mon, May 11, 2020 at 5:11 PM Christoph Hellwig <hch@lst.de> wrote:
> On Mon, May 11, 2020 at 09:40:39AM +0200, Geert Uytterhoeven wrote:
> > On Sun, May 10, 2020 at 9:57 AM Christoph Hellwig <hch@lst.de> wrote:
> > >
> > > flush_icache_range generally operates on kernel addresses, but for some
> > > reason m68k needed a set_fs override.  Move that into the m68k code
> > > insted of keeping it in the module loader.
> > >
> > > Signed-off-by: Christoph Hellwig <hch@lst.de>
> >
> > Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
> > Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
>
> Btw, do you know what part of flush_icache_range relied on set_fs?
> Do any of the m68k maintainers have an idea how to handle that in
> a nicer way when we can split the implementations?

arch/m68k/mm/cache.c:virt_to_phys_slow()

All instructions that look up addresses in the page tables look at the
source/destination function codes (SFC/DFC) to know if they have to use
the supervisor or user page tables.
So the actual implementation is the same: set_fs() merely configures
SFC/DFC, to select the address space to use.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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