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

[John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>]

Hi Baoquan,

On Thu, 2024-08-22 at 17:17 +0800, Baoquan He wrote:
> > 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
> 
> If so, fix need be made.
> 
> We may need change in ARCH_SUPPORTS_CRASH_DUMP of ppc, can you or anyone
> post a patch? I don't know how to identify 32-bit Power Macintosh.
> 
> arch/powerpc/Kconfig:
> ===
> config ARCH_SUPPORTS_CRASH_DUMP
>         def_bool PPC64 || PPC_BOOK3S_32 || PPC_85xx || (44x && !SMP)
>         
> config ARCH_SELECTS_CRASH_DUMP
>         def_bool y
>         depends on CRASH_DUMP
>         select RELOCATABLE if PPC64 || 44x || PPC_85xx
> ......
> config PHYSICAL_START
>         hex "Physical address where the kernel is loaded" if PHYSICAL_START_BOOL
>         default "0x02000000" if PPC_BOOK3S && CRASH_DUMP && !NONSTATIC_KERNEL
>         default "0x00000000"

I think the architecture does support crash dumps, but I think the kernel has to
be booted from kexec in this case. Booting a kernel with CRASH_DUMP enabled won't
work from Open Firmware. So, I think CRASH_DUMP should just be disabled for
PPC_BOOK3S_32 by default and users who want to use it on these systems, will have to
enable it explicitly.

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
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