linux-kernel - Re: [PATCH -mm 1/2] kexec jump -v12: kexec jump

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Date:	Mon, 7 Jul 2008 14:50:11 +0200
From:	Pavel Machek <pavel@...e.cz>
To:	Huang Ying <ying.huang@...el.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	nigel@...el.suspend2.net, "Rafael J. Wysocki" <rjw@...k.pl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Vivek Goyal <vgoyal@...hat.com>, linux-kernel@...r.kernel.org,
	linux-pm@...ts.linux-foundation.org,
	Kexec Mailing List <kexec@...ts.infradead.org>
Subject: Re: [PATCH -mm 1/2] kexec jump -v12: kexec jump

Hi!

The patch looks mostly ok to me. (Perhaps there's time to split it
into smaller chunks?)

You can add Acked-by: Pavel Machek <pavel@...e.cz> to it, I guess.


> This patch provides an enhancement to kexec/kdump. It implements
> the following features:
> 
> - Backup/restore memory used by the original kernel before/after
>   kexec.
> 
> - Save/restore CPU state before/after kexec.
> 
> The features of this patch can be used as a general method to call
> program in physical mode (paging turning off). This can be used to
> call BIOS code under Linux.
> 
> 
> kexec-tools needs to be patched to support kexec jump. The patches and
> the precompiled kexec can be download from the following URL:
> 
>        source: http://khibernation.sourceforge.net/download/release_v10/kexec-tools/kexec-tools-src_git_kh10.tar.bz2
>        patches: http://khibernation.sourceforge.net/download/release_v10/kexec-tools/kexec-tools-patches_git_kh10.tar.bz2
>        binary: http://khibernation.sourceforge.net/download/release_v10/kexec-tools/kexec_git_kh10
> 
> 
> Usage example of calling some physical mode code and return:

> @@ -98,16 +101,24 @@ int machine_kexec_prepare(struct kimage 
>   */
>  void machine_kexec_cleanup(struct kimage *image)
>  {
> +	if (nx_enabled)
> +		set_pages_nx(image->control_code_page, 1);
>  }

, 0 ? (setup and cleanup were same, which is strange).



> @@ -1411,3 +1421,50 @@ static int __init crash_save_vmcoreinfo_
>  }
>  
>  module_init(crash_save_vmcoreinfo_init)
> +
> +/**
> + *	kernel_kexec - reboot the system

Really?

> + *	Move into place and start executing a preloaded standalone
> + *	executable.  If nothing was preloaded return an error.
> + */
> +int kernel_kexec(void)
> +{
> +	int error = 0;
> +
> +	if (xchg(&kexec_lock, 1))
> +		return -EBUSY;

That's quite a strange way to provide a lock. mutex_trylock?


> +	if (!kexec_image) {
> +		error = -EINVAL;
> +		goto Unlock;
> +	}
> +
> +	if (kexec_image->preserve_context) {
> +#ifdef CONFIG_KEXEC_JUMP
> +		local_irq_disable();
> +		save_processor_state();

#else
	BUG()

...because otherwise you silently do nothing?

> +#endif
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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