linux-kernel - Re: [PATCH 4/6] kexec: A new system call, kexec_file

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Message-ID: <20131204173238.GD19087@redhat.com>
Date:	Wed, 4 Dec 2013 12:32:39 -0500
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Baoquan He <bhe@...hat.com>
Cc:	linux-kernel@...r.kernel.org, kexec@...ts.infradead.org,
	mjg59@...f.ucam.org, greg@...ah.com, ebiederm@...ssion.com,
	hpa@...or.com
Subject: Re: [PATCH 4/6] kexec: A new system call, kexec_file_load, for in
 kernel kexec

On Wed, Dec 04, 2013 at 09:56:57AM +0800, Baoquan He wrote:
> On 11/20/13 at 12:50pm, Vivek Goyal wrote:
> > + * that kexec_mutex is held.
> > + */
> 
> I think kexec_add_buffer is guaranteed to be called before allocating
> control pages, why not updating image->control_page after each time
> kexec_add_buffer is called. Then when control page is needed, effective
> address in crash_kernel region can be given. This can be a little more
> efficient.

image->control_page controls the lowest address available for control
pages in crash kernel region. When we do kexec_add_buffer, we don't
necessarily know whether there is an empty page available between
segments or not.

Also, existing logic for kexec does not update the image->control_page
when segments are being copied.

So I think this does not offer any huge benefits and it is not performance
critical path. I will just leave it as it is.

Thanks
Vivek
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