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

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Message-ID: <20140107143723.GB1524@redhat.com>
Date:	Tue, 7 Jan 2014 09:37:23 -0500
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Dave Young <dyoung@...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 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.

Thanks
Vivek
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