On Wed, Feb 14, 2018 at 10:17 AM, Bhupesh SHARMA <bhupesh.linux@xxxxxxxxx> wrote: > On Wed, Feb 14, 2018 at 2:32 PM, Gi-Oh Kim <gi-oh.kim@xxxxxxxxxxxxxxxx> wrote: >> On Wed, Feb 14, 2018 at 2:43 AM, Dave Young <dyoung@xxxxxxxxxx> wrote: >>> Hi, >>> On 02/13/18 at 04:22pm, Gioh Kim wrote: >>>> Jumping between the system kernel and the dump-capture kernel >>>> has been supported for long time but there is no description >>>> how to use it. This patch adds the description how to use kexec tool >>>> to jump to the dump-capture kernel and jump back to the system kernel. >>> >>> I do not think this should belong to kdump documentation. There are a >>> lot of choices after a vmcore saving, one can reboot, halt, even go >>> ahead with real root filesystem init path. We do not need to document >>> all these in kdump.txt. >>> >>> Since it is a general use case not only for kdump, add more info in >>> kexec man page would be better. >> >> Hi, >> >> Whenever I find a kernel option, I search Documentation files, and >> next is google. >> So I think it would be better to describe how to use a kernel option >> or kernel feature in kernel document. > > But this is not the kernel documentation for kexec warm reboot. > Instead this is the kdump documentation. The example you quoted above > is the 'kexec -l' use case and not 'kexec -p'. I thought enabling CONFIG_KEXEC_JUMP in kernel is the main topic and describing 'kexec -l' is showing how to use the CONFIG_KEXEC_JUMP option. Ok, I'll check the manual page of kexec. I think it would be enough if I add a short note for -l and --load-preserve-context about the kernel option. Thank you ;-) > > Rather the man page for kexec-tools should be a good place to include > this documentation. > > Regards, > Bhupesh > >>> >>>> >>>> Signed-off-by: Gioh Kim <gi-oh.kim@xxxxxxxxxxxxxxxx> >>>> --- >>>> Documentation/kdump/kdump.txt | 38 ++++++++++++++++++++++++++++++++++++++ >>>> 1 file changed, 38 insertions(+) >>>> >>>> diff --git a/Documentation/kdump/kdump.txt b/Documentation/kdump/kdump.txt >>>> index 51814450a7f8..35b71fef5d88 100644 >>>> --- a/Documentation/kdump/kdump.txt >>>> +++ b/Documentation/kdump/kdump.txt >>>> @@ -460,6 +460,44 @@ and the system will boot into the dump-capture kernel. >>>> For testing purposes, you can trigger a crash by using "ALT-SysRq-c", >>>> "echo c > /proc/sysrq-trigger" or write a module to force the panic. >>>> >>>> +Jump between the System kernel and the Dump-capture kernel >>>> +=============================== >>>> + >>>> +Without system crash, the system can jump to the dump-capture kernel. >>>> + >>>> +1) Enable "jump between system kernel and dump-capture kernel" support under >>>> + "Processor type and features" >>>> + >>>> + CONFIG_KEXEC_JUMP=y >>>> + >>>> +2) Load the dump-capture kernel with --load-preserve-context and mem-max >>>> + options as following. >>>> + >>>> + kexec -l <dump-capture-kernel-vmlinux-image> \ >>>> + --initrd=<initrd-for-dump-capture-kernel> --args-linux \ >>>> + --append="root=<root-dev> <arch-specific-options>" \ >>>> + --load-preserve-context \ >>>> + --mem-max=<the highest memory address addr to load code into> >>>> + >>>> +3) Jump to the loaded kernel >>>> + >>>> + kexec -e >>>> + >>>> +Now the system is running with the dump-capture kernel. You can jump back >>>> +to the system kernel. >>>> + >>>> +1) Find kexec_jump_back_entry address in kernel booting parameters in >>>> + /proc/cmdline. That is the address for kexec to jump to. For example: >>>> + kexec_jump_back_entry=0x00000000000810d2 >>>> + >>>> +2) Following command sets the jump-back address for kexec. >>>> + >>>> + kexec --load-jump-back-helper --entry=0x810d2 >>>> + >>>> +3) Jump to the system kernel >>>> + >>>> + kexec -e >>>> + >>>> Write Out the Dump File >>>> ======================= >>>> >>>> -- >>>> 2.11.0 >>>> >>> >>> Thanks >>> Dave >> >> >> >> -- >> GIOH KIM >> Linux Kernel Entwickler >> >> ProfitBricks GmbH >> Greifswalder Str. 207 >> D - 10405 Berlin >> >> Tel: +49 176 2697 8962 >> Fax: +49 30 577 008 299 >> Email: gi-oh.kim@xxxxxxxxxxxxxxxx >> URL: https://www.profitbricks.de >> >> Sitz der Gesellschaft: Berlin >> Registergericht: Amtsgericht Charlottenburg, HRB 125506 B >> Geschäftsführer: Achim Weiss, Matthias Steinberg -- GIOH KIM Linux Kernel Entwickler ProfitBricks GmbH Greifswalder Str. 207 D - 10405 Berlin Tel: +49 176 2697 8962 Fax: +49 30 577 008 299 Email: gi-oh.kim@xxxxxxxxxxxxxxxx URL: https://www.profitbricks.de Sitz der Gesellschaft: Berlin Registergericht: Amtsgericht Charlottenburg, HRB 125506 B Geschäftsführer: Achim Weiss, Matthias Steinberg _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
