lkml.org 
[lkml]   [2017]   [Aug]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: arch/arm/kernel/setup.c fails to compile for NOMMU
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?
---
From 2707f3bf00181bbc9dcf6a1f287eb7369141e955 Mon Sep 17 00:00:00 2001
From: Michal Hocko <mhocko@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 <mhocko@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

\
 
 \ /
  Last update: 2017-08-25 08:46    [W:0.065 / U:0.148 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site