linux-kernel - Re: [PATCH] mm: provide a fallback for PAGE_KERNEL

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Date:   Wed, 2 May 2018 15:11:13 +0000
From:   "Luis R. Rodriguez" <mcgrof@...nel.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Linux-Arch <linux-arch@...r.kernel.org>,
        Linux FS Devel <linux-fsdevel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-m68k <linux-m68k@...ts.linux-m68k.org>
Subject: Re: [PATCH] mm: provide a fallback for PAGE_KERNEL_RO for
 architectures

On Wed, May 02, 2018 at 12:08:57PM +0200, Geert Uytterhoeven wrote:
> Hi Luis,
> 
> On Sat, Apr 28, 2018 at 2:15 AM, Luis R. Rodriguez <mcgrof@...nel.org> wrote:
> > Some architectures do not define PAGE_KERNEL_RO, best we can do
> > for them is to provide a fallback onto PAGE_KERNEL. Remove the
> > hack from the firmware loader and move it onto the asm-generic
> > header, and document while at it the affected architectures
> > which do not have a PAGE_KERNEL_RO:
> >
> >   o alpha
> >   o ia64
> >   o m68k
> >   o mips
> >   o sparc64
> >   o sparc
> >
> > Blessed-by: 0-day
> > Signed-off-by: Luis R. Rodriguez <mcgrof@...nel.org>
> 
> I believe the "best we can do" is to add the missing definitions for the
> architectures where the hardware does support it?

True, but we cannot wait for every architecture to implement a feature to then
such generics upstream, specially when we have common places which use that.
Matthew did send a patch to add ia64 support for PAGE_KERNEL_RO, so I'll
respin the patch to add that and also move the other define he suggested.

At least we'd now have a list of documented archs which need further work too.

  Luis