Re: Build regressions/improvements in v4.3-rc7

[Russell King - ARM Linux <linux@arm.linux.org.uk>]

On Sun, Oct 25, 2015 at 11:39:15AM +0100, Geert Uytterhoeven wrote:
> On Sun, Oct 25, 2015 at 11:18 AM, Geert Uytterhoeven
> <geert@linux-m68k.org> wrote:
> > On Sun, Oct 25, 2015 at 11:12 AM, Geert Uytterhoeven
> > <geert@linux-m68k.org> wrote:
> >> JFYI, when comparing v4.3-rc7[1] to v4.3-rc6[3], the summaries are:
> >>   - build errors: +12/-4
> 
> >   + /home/kisskb/slave/src/arch/arm/kernel/patch.c: error: 'L_PTE_DIRTY' undeclared (first use in this function):  => 39:2
> >   + /home/kisskb/slave/src/arch/arm/kernel/patch.c: error: 'L_PTE_MT_WRITEBACK' undeclared (first use in this function):  => 39:2
> >   + /home/kisskb/slave/src/arch/arm/kernel/patch.c: error: 'L_PTE_PRESENT' undeclared (first use in this function):  => 39:2
> >   + /home/kisskb/slave/src/arch/arm/kernel/patch.c: error: 'L_PTE_XN' undeclared (first use in this function):  => 39:2
> >   + /home/kisskb/slave/src/arch/arm/kernel/patch.c: error: 'L_PTE_YOUNG' undeclared (first use in this function):  => 39:2
> 
> Caused by:
> 
> commit ab0615e2d6fb074764a3e4d05f1326fa2fdb4627
> Author: Rabin Vincent <rabin@rab.in>
> Date:   Thu Apr 24 23:28:57 2014 +0200
> 
>     arm: use fixmap for text patching when text is RO
> 
> Should the call to set_fixmap() in arch/arm/kernel/patch.c
> just be protected by #ifdef CONFIG_MMU?

What this shows, time and time again, is that we need better testing for
!MMU platforms - we need !MMU platforms in the mainline kernel which
people actually have.

I have an OKI 67001 board (from Simtec), which is the older generation of
!MMU system, and I have code for it, but arm-soc won't let me put it in
the mainline kernel - even though it would give me a platform which I can
add to the boot farm to build and boot a test kernel for.

Consequently, I've little motivation to catch !MMU regressions before
they hit mainline.

Should we accept old !MMU code into mainline for platforms which kernel
developers have, in order to aid testing, even though it isn't modern
platforms and doesn't conform to the latest way of doing stuff.

Discuss.

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