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'. 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 _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
