linux-kernel - Re: [PATCH] arm: make kexec depend on MMU

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Date:   Thu, 06 Feb 2020 01:10:22 +0100
From:   Stefan Agner <stefan@...er.ch>
To:     Russell King - ARM Linux admin <linux@...linux.org.uk>
Cc:     arnd@...db.de, linus.walleij@...aro.org, akpm@...ux-foundation.org,
        nsekhar@...com, mchehab+samsung@...nel.org,
        bgolaszewski@...libre.com, armlinux@...isordat.com,
        benjamin.gaignard@...aro.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH] arm: make kexec depend on MMU

On 2020-02-06 00:53, Russell King - ARM Linux admin wrote:
> Does patch 8951/1, which has been merged into mainline, not fix this?

Yes, that should take care of it. 

I discussed end of last year with Michal about this, and back then that
patch wasn't around. Should have checked master before re-sending this
patch. Sorry for the noise.

--
Stefan


> On Wed, Feb 05, 2020 at 11:43:44PM +0100, Stefan Agner wrote:
>> From: Michal Hocko <mhocko@...e.com>
>>
>> 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@...e.com>
>> Reviewed-by: Stefan Agner <stefan@...er.ch>
>> Signed-off-by: Stefan Agner <stefan@...er.ch>
>> ---
>>  arch/arm/Kconfig | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
>> index 96dab76da3b3..59ce8943151f 100644
>> --- a/arch/arm/Kconfig
>> +++ b/arch/arm/Kconfig
>> @@ -1906,6 +1906,7 @@ 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
>> --
>> 2.25.0
>>
>>