linux-kernel - Re: [PATCH] crash: Default to CRASH_DUMP=n when support for it is unlikely

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Message-ID: <Zs1wpHxfTcwKr517@MiWiFi-R3L-srv>
Date: Tue, 27 Aug 2024 14:22:28 +0800
From: Baoquan He <bhe@...hat.com>
To: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
Cc: Geert Uytterhoeven <geert@...ux-m68k.org>,
	Dave Vasilevsky <dave@...ilevsky.ca>, linuxppc-dev@...ts.ozlabs.org,
	linux-sh@...r.kernel.org, mpe@...erman.id.au,
	kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Reimar Döffinger <Reimar.Doeffinger@....de>
Subject: Re: [PATCH] crash: Default to CRASH_DUMP=n when support for it is
 unlikely

On 08/23/24 at 08:16pm, John Paul Adrian Glaubitz wrote:
> Hi Geert,
> 
> On Fri, 2024-08-23 at 15:13 +0200, Geert Uytterhoeven wrote:
> > IMHO CRASH_DUMP should just default to n, like most kernel options, as
> > it enables non-trivial extra functionality: the kernel source tree has
> > more than 100 locations that check if CONFIG_CRASH_DUMP is enabled.
> 
> I guess we should then revert that part of Baoquan's original patch.
> 
> > What is so special about CRASH_DUMP, that it should be enabled by
> > default?
> 
> Let's ask Baoquan who made the original change to enable CRASH_DUMP by default.

Sorry for late reply.

It's me who enabled it by default when I clean up the messy Kconfig items
related to kexec/kdump. Before the clean up, CONFIG_CRASH_DUMP only
controlled a very small file including sevearl functions and macro
definitions. But kernel codes took CRASH_DUMP as switch of kdump.

About why it's enabled by default, as Michael has explained in another
thread, distros usualy needs to enable it by default because vmcore
dumping is a very important feature on servers, even guest instances. 
Even though kdump codes are enabled to built in, not providing
crashkernel= value won't make vmcore dumping take effect, it won't cost
system resources in that case.

Thanks
Baoquan