linux-kernel - Re: kexec: reuse 1st kernel as kexec/kdump kernel?

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Date:	Wed, 8 Jan 2014 09:24:22 +0800
From:	Dave Young <dyoung@...hat.com>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
	ebiederm@...ssion.com, hpa@...or.com
Subject: Re: kexec: reuse 1st kernel as kexec/kdump kernel?

On 01/07/14 at 09:37am, Vivek Goyal wrote:
> On Tue, Jan 07, 2014 at 10:34:06AM +0800, Dave Young wrote:
> > Hi, all
> > 
> > I have a question in mind: can we copy and prepare kexec kernel while
> > normal booting?
> > 
> > Just like below wild idea:
> > 
> > Kernel uncompress itself (assume kernel is relocatable)
> > -> copy the kernel image somewhere for backup
> >   -> reserver crashkernel memory
> >     -> copy the backuped kernel image/initrd image to reserved memory
> >       -> copy the purgatory which can be embedded in elf section?
> >         -> prepare the e820 memory ranges which is for kdump kernel
> > 
> > So userspace only need to call kexec reboot, kexec_load is not necessary.
> > The initrd for kdump should be different, but we can add some different logic
> > which will be only for kdump and it can be skipped in normal boot.
> > 
> > Is it doable?
> 
> What's the advantage of doing all this? Why are you trying to skip load
> step.

Hi, Vivek

It's just a thought that kernel already have all the information for kexecing so
we can save user space works. Rethinking about it it benefits more to kexec than
kdump. For kexec user he can reboot with kexec without any user space actions.
For kdump there's no much advantage though.

Thanks
Dave
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