From mboxrd@z Thu Jan  1 00:00:00 1970
From: Vitaly Kuznetsov <vkuznets@redhat.com>
Subject: Re: [PATCH v4 0/9] toolstack-based approach to pvhvm
	guest kexec
Date: Thu, 04 Dec 2014 15:29:12 +0100
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	<20141204111715.GA15916@aepfle.de>
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To: Olaf Hering <olaf@aepfle.de>
Cc: Wei Liu <wei.liu2@citrix.com>, Andrew Jones <drjones@redhat.com>, Keir Fraser <keir@xen.org>, Ian Campbell <ian.campbell@citrix.com>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>, Andrew Cooper <andrew.cooper3@citrix.com>, Ian Jackson <ian.jackson@eu.citrix.com>, Tim Deegan <tim@xen.org>, David Vrabel <david.vrabel@citrix.com>, Jan Beulich <jbeulich@suse.com>, xen-devel@lists.xenproject.org
List-Id: xen-devel@lists.xenproject.org

Olaf Hering <olaf@aepfle.de> writes:

> On Wed, Dec 03, Vitaly Kuznetsov wrote:
>
>> Original description:
>> 
>> When a PVHVM linux guest performs kexec there are lots of things which
>> require taking care of:
>> - shared info, vcpu_info
>> - grants
>> - event channels
>> - ...
>> Instead of taking care of all these things we can rebuild the domain
>> performing kexec from scratch doing so-called soft-reboot.
>> 
>> The idea was suggested by David Vrabel, Jan Beulich, and Konrad Rzeszutek Wilk.
>> 
>> P.S. The patch series can be tested with PVHVM Linux guest with the following
>> modifications:
>
> Its not clear to me how thew old kernel starts the new kernel.
> How and where is that done?

It is done by linux kernel itself, I bring nothing new into the
picture. It all works like this:
1) Original guest does HYPERVISOR_sched_op(SCHEDOP_shutdown, r = { .reason =
SHUTDOWN_soft_reset})
2) All this rebuild machinery happens including copying HVM context
3) New guest resumes from where old did the hypercall
4) Kernel does kexec and new kernel is being booted.

>
> Olaf

-- 
  Vitaly