linux-kernel - Re: [PATCH linux-next v3 05/14] crash: clean up kdump related config items

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Message-ID: <a9d9ecd1ed8d62eae47ec26257093495e6cbd44a.camel@physik.fu-berlin.de>
Date: Thu, 22 Aug 2024 09:33:56 +0200
From: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
To: Baoquan He <bhe@...hat.com>, linux-kernel@...r.kernel.org
Cc: Dave Vasilevsky <dave@...ilevsky.ca>, Michael Ellerman
 <mpe@...erman.id.au>,  kexec@...ts.infradead.org,
 debian-powerpc@...ts.debian.org, x86@...nel.org, 
 linux-arm-kernel@...ts.infradead.org, linuxppc-dev@...ts.ozlabs.org, 
 linux-s390@...r.kernel.org, linux-sh@...r.kernel.org,
 linux-mips@...r.kernel.org,  linux-riscv@...ts.infradead.org,
 loongarch@...ts.linux.dev,  akpm@...ux-foundation.org,
 ebiederm@...ssion.com, hbathini@...ux.ibm.com,  piliu@...hat.com,
 viro@...iv.linux.org.uk, Sam James <sam@...too.org>
Subject: Re: [PATCH linux-next v3 05/14] crash: clean up kdump related
 config items

Hi Baoquan,

On Wed, 2024-01-24 at 13:12 +0800, Baoquan He wrote:
> By splitting CRASH_RESERVE and VMCORE_INFO out from CRASH_CORE, cleaning
> up the dependency of FA_DMUMP on CRASH_DUMP, and moving crash codes from
> kexec_core.c to crash_core.c, now we can rearrange CRASH_DUMP to
> depend on KEXEC_CORE, and make CRASH_DUMP select CRASH_RESERVE and
> VMCORE_INFO.
> 
> KEXEC_CORE won't select CRASH_RESERVE and VMCORE_INFO any more because
> KEXEC_CORE enables codes which allocate control pages, copy
> kexec/kdump segments, and prepare for switching. These codes are shared
> by both kexec reboot and crash dumping.
> 
> Doing this makes codes and the corresponding config items more
> logical (the right item depends on or is selected by the left item).
> 
> PROC_KCORE -----------> VMCORE_INFO
> 
>            |----------> VMCORE_INFO
> FA_DUMP----|
>            |----------> CRASH_RESERVE
> 
>                                                 ---->VMCORE_INFO
>                                                /
>                                                |---->CRASH_RESERVE
> KEXEC      --|                                /|
>              |--> KEXEC_CORE--> CRASH_DUMP-->/-|---->PROC_VMCORE
> KEXEC_FILE --|                               \ |
>                                                \---->CRASH_HOTPLUG
> 
> KEXEC      --|
>              |--> KEXEC_CORE--> kexec reboot
> KEXEC_FILE --|
> 
> Signed-off-by: Baoquan He <bhe@...hat.com>
> ---
>  kernel/Kconfig.kexec | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/Kconfig.kexec b/kernel/Kconfig.kexec
> index 8faf27043432..6c34e63c88ff 100644
> --- a/kernel/Kconfig.kexec
> +++ b/kernel/Kconfig.kexec
> @@ -9,8 +9,6 @@ config VMCORE_INFO
>  	bool
>  
>  config KEXEC_CORE
> -	select VMCORE_INFO
> -	select CRASH_RESERVE
>  	bool
>  
>  config KEXEC_ELF
> @@ -99,8 +97,11 @@ config KEXEC_JUMP
>  
>  config CRASH_DUMP
>  	bool "kernel crash dumps"
> +	default y
>  	depends on ARCH_SUPPORTS_CRASH_DUMP
> -	select KEXEC_CORE
> +	depends on KEXEC_CORE
> +	select VMCORE_INFO
> +	select CRASH_RESERVE
>  	help
>  	  Generate crash dump after being started by kexec.
>  	  This should be normally only set in special crash dump kernels

The change to enable CONFIG_CRASH_DUMP by default apparently broke the boot
on 32-bit Power Macintosh systems which fail after GRUB with:

	"Error: You can't boot a kdump kernel from OF!"

We may have to turn this off for 32-bit Power Macintosh systems.

See this thread on debian-powerpc ML: https://lists.debian.org/debian-powerpc/2024/07/msg00001.html

Thanks,
Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer
`. `'   Physicist
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913