On Fri 25-08-17 08:45:40, Michal Hocko wrote:
> On Thu 24-08-17 17:17:41, Russell King - ARM Linux wrote:
> > On Fri, Aug 18, 2017 at 01:24:02PM +0200, Michal Hocko wrote:
> > > Hi Russel,
> > > I have a battery of configs for compile testing and for some time I've
> > > been seeing the following compilation error with nommu config (attached)
> > >
> > > arch/arm/kernel/setup.c: In function 'reserve_crashkernel':
> > > arch/arm/kernel/setup.c:1005:25: error: 'SECTION_SIZE' undeclared (first
> > > use in this function)
> > > crash_size, SECTION_SIZE);
> > >
> > > I didn't get to look what is going on here, maybe my config is just too
> > > artificial but the primary reason is that SECTION_SIZE is not defined in
> > > pgtable-nommu.h. To be honest I am not familiar with nommu very much and
> > > it smells like the whole reserve_crashkernel doesn't really make any
> > > sense on those configs. Could you have a look what is the best fix
> > > please?
> >
> > Hi,
> >
> > I suspect that mach-netx has never been tested in nommu configurations
> > (ditto for many of the older platforms, which pre-date merging nommu
> > support.)
> >
> > Maybe the best solution is to make these old platforms depend on MMU.
> >
> > However, I'm wondering whether kexec makes sense for !MMU - that's
> > probably something that hasn't been tested and doesn't actually work.
> > So maybe another approach would be to make kexec depend on MMU for
> > ARM - but I'm afraid I don't really know.
>
> Yeah, I've disabled KEXEC in my testing config. All I do care about is
> to test nommu specific code paths in MM code.
>
> > I only have very limited nommu experience.
>
> me too
>
> So what would you say about the following?
It's been some time and it seems this has fallen between cracks. Is this
worth puruing or I should just forget about it and drop it on the floor?
> ---
> From 2707f3bf00181bbc9dcf6a1f287eb7369141e955 Mon Sep 17 00:00:00 2001
> From: Michal Hocko <mho...@suse.com>
> Date: Fri, 25 Aug 2017 08:40:09 +0200
> Subject: [PATCH] arm: make kexec depend on MMU
>
> arm nommu config with KEXEC enabled doesn't compile
> arch/arm/kernel/setup.c: In function 'reserve_crashkernel':
> arch/arm/kernel/setup.c:1005:25: error: 'SECTION_SIZE' undeclared (first
> use in this function)
> crash_size, SECTION_SIZE);
>
> since 61603016e212 ("ARM: kexec: fix crashkernel= handling") which is
> over one year without anybody noticing. I have only noticed beause of
> my testing nommu config which somehow gained CONFIG_KEXEC without
> an intention. This suggests that nobody is actually using KEXEC
> on nommu ARM configs. It is even a question whether kexec works with
> nommu.
>
> Make KEXEC depend on MMU to make this clear. If somebody wants to enable
> there will be probably more things to take care.
>
> Signed-off-by: Michal Hocko <mho...@suse.com>
> ---
> arch/arm/Kconfig | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 3f4aa9179337..c8603195d7fc 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -2003,6 +2003,7 @@ config KEXEC
> bool "Kexec system call (EXPERIMENTAL)"
> depends on (!SMP || PM_SLEEP_SMP)
> depends on !CPU_V7M
> + depends on MMU
> select KEXEC_CORE
> help
> kexec is a system call that implements the ability to shutdown your
> --
> 2.13.2
>
> --
> Michal Hocko
> SUSE Labs
--
Michal Hocko
SUSE Labs
