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. > >> >> 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 -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
