[linux-pm] [RFC][PATCH 0/2 -mm] kexec based hibernation -v3

[huang ying]

On 9/21/07, Mika Penttilä <mika.penttila at kolumbus.fi> wrote:
> huang ying wrote:
> > On 9/21/07, Mika Penttilä <mika.penttila at kolumbus.fi> wrote:
> >
> >>> Usage:
> >>>
> >>> 1. Compile kernel with following options selected:
> >>>
> >>> CONFIG_X86_32=y
> >>> CONFIG_RELOCATABLE=y # not needed strictly, but it is more convenient with it
> >>> CONFIG_KEXEC=y
> >>> CONFIG_CRASH_DUMP=y # only needed by kexeced kernel to save/restore memory image
> >>> CONFIG_PM=y
> >>> CONFIG_KEXEC_JUMP=y
> >>>
> >>> 2. Download the kexec-tools-testing git tree, apply the kexec-tools
> >>>    kjump patches (or download the source tar ball directly) and
> >>>    compile.
> >>>
> >>> 3. Download and compile the krestore tool.
> >>>
> >>> 4. Prepare 2 root partition used by kernel A and kernel B/C, referred
> >>>    as /dev/hda, /dev/hdb in following text. This is not strictly
> >>>    necessary, I use this scheme for testing during development.
> >>>
> >>> 5. Boot kernel compiled for normal usage (kernal A).
> >>>
> >>> 6. Load kernel compiled for hibernating/restore usage (kernel B) with
> >>>    kexec, the same kernel as that of 5 can be used if
> >>>    CONFIG_RELOCATABLE=y and CONFIG_CRASH_DUMP=y are selected.
> >>>
> >>>    The --elf64-core-headers should be specified in command line of
> >>>    kexec, because only the 64bit ELF is supported by krestore tool.
> >>>
> >>>    For example, the shell command line can be as follow:
> >>>
> >>>    kexec -p -n /boot/bzImage --mem-min=0x100000 --mem-max=0xffffff
> >>>        --elf64-core-headers --append="root=/dev/hdb single"
> >>>
> >>> 7. Jump to the hibernating kernel (kernel B) with following shell
> >>>    command line:
> >>>
> >>>    kexec -j
> >>>
> >>> 8. In the hibernating kernel (kernel B), the memory image of
> >>>    hibernated kernel (kernel A) can be saved as follow:
> >>>
> >>>    cp /proc/vmcore .
> >>>    cp /sys/kernel/kexec_jump_back_entry .
> >>>
> >>>
> >> Here we save also kernel B's pages.
> >>
> >
> > No, the kernel B's pages will not be saved. Because when we build the
> > elfcore (/proc/vmcore) header, we exclude memory area used by kernel
> > B. The details can be found in kexec-tools patches.
> >
> >
> Ok I see. But should the kernel B's e820 mem map be limited to 1m-16m in
> order not to allocate pages found also in A's space? Or does does the
> --mem-min and --mem-max do that also?

That is what "memmap=exactmap memmap=640K at 0K memmap=15M at 1M" for. The
contents of e820 memmap will be overrided when these kernel parameters
are specified.

Best Regards,
Huang Ying