Re: [Xen-devel] [PATCH v4 0/9] toolstack-based approach to pvhvm guest kexec

[Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>]

Olaf Hering <olaf@xxxxxxxxx> 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

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