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Date:   Mon, 5 Jul 2021 13:51:13 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Geert Uytterhoeven <geert@linux-m68k.org>
Cc:     Christoph Hellwig <hch@lst.de>, Greg Ungerer <gerg@linux-m68k.org>,
        linux-m68k <linux-m68k@lists.linux-m68k.org>,
        uClinux development list <uclinux-dev@uclinux.org>,
        Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH] m68knommu: remove set_fs()
Message-ID: <20210705115113.GA20126@lst.de>
References: <20210705055719.949875-1-hch@lst.de> <20210705055719.949875-2-hch@lst.de> <CAMuHMdV4UQaKE7fn0_HhPfHzwEMwouPvqoeW6_V13yebe7ZSQQ@mail.gmail.com> <20210705085607.GA6827@lst.de> <CAMuHMdXB1aYK+jUtkf0L5UCNt2HCH53gxY2rDxYHCNFVSG91yw@mail.gmail.com>
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On Mon, Jul 05, 2021 at 01:33:39PM +0200, Geert Uytterhoeven wrote:
> > No, at least not yet.  Coldfire and co still rely on set_fs for various
> > things in the m68k arch code, and also don't provide
> > __{get,put}_kernel_nofault yet.  So wile m68k with CPU_HAS_ADDRESS_SPACES
> > will probably one of the hardest ports to get rid of set_fs() for,
> > m68k/mmu without CPU_HAS_ADDRESS_SPACES would be a logical next step.
> > I could try to whiteboard code some of it, but I'd need help from dedicated
> 
> M68k/mmu with CPU_HAS_ADDRESS_SPACES needs to use the address spaces
> to access user space from kernel space using the "moves" instruction.
> Coldfire doesn't.
> 
> See arch/m68k/include/asm/uaccess.h.

I know.  That doesn't change that:

 a) even getting rid for MMMU && !CPU_HAS_ADDRESS_SPACES requires further
    work
 b) getting rid of set_fs is possible even for CPU_HAS_ADDRESS_SPACES,
    although it requires a lot of work.