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

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Message-ID: <46F3DFA4.90909@kolumbus.fi>
Date:	Fri, 21 Sep 2007 18:13:40 +0300
From:	Mika Penttilä <mika.penttila@...umbus.fi>
To:	huang ying <huang.ying.caritas@...il.com>
CC:	"Huang, Ying" <ying.huang@...el.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Pavel Machek <pavel@....cz>, nigel@...el.suspend2.net,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jeremy Maitin-Shepard <jbms@....edu>,
	linux-pm@...ts.linux-foundation.org,
	Kexec Mailing List <kexec@...ts.infradead.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [linux-pm] [RFC][PATCH 0/2 -mm] kexec based hibernation -v3

huang ying wrote:
> On 9/21/07, Mika Penttilä <mika.penttila@...umbus.fi> wrote:
>   
>> huang ying wrote:
>>     
>>> On 9/21/07, Mika Penttilä <mika.penttila@...umbus.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@0K memmap=15M@1M" for. The
> contents of e820 memmap will be overrided when these kernel parameters
> are specified.
>
> Best Regards,
> Huang Ying
>   
Yes, you just didn't specify exactmap for kernel B in your instructions, 
but only for C. But it is also required for kernel B then?

Thanks,
Mika

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