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Re: [PATCH] spapr: Migrate CAS reboot flag

From: Cédric Le Goater
Subject: Re: [PATCH] spapr: Migrate CAS reboot flag
Date: Wed, 22 Jan 2020 15:08:49 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2

On 1/22/20 1:47 PM, Greg Kurz wrote:
> On Wed, 15 Jan 2020 19:10:47 +0100
> Cédric Le Goater <address@hidden> wrote:
>> On 1/15/20 6:48 PM, Greg Kurz wrote:
>>> Migration can potentially race with CAS reboot. If the migration thread
>>> completes migration after CAS has set spapr->cas_reboot but before the
>>> mainloop could pick up the reset request and reset the machine, the
>>> guest is migrated unrebooted and the destination doesn't reboot it
>>> either because it isn't aware a CAS reboot was needed (eg, because a
>>> device was added before CAS). This likely result in a broken or hung
>>> guest.
>>> Even if it is small, the window between CAS and CAS reboot is enough to
>>> re-qualify spapr->cas_reboot as state that we should migrate. Add a new
>>> subsection for that and always send it when a CAS reboot is pending.
>>> This may cause migration to older QEMUs to fail but it is still better
>>> than end up with a broken guest.
>>> The destination cannot honour the CAS reboot request from a post load
>>> handler because this must be done after the guest is fully restored.
>>> It is thus done from a VM change state handler.
>>> Reported-by: Lukáš Doktor <address@hidden>
>>> Signed-off-by: Greg Kurz <address@hidden>
>> Cédric Le Goater <address@hidden>
> I guess you mean:
> Reviewed-by: Cédric Le Goater <address@hidden>


   Reviewed-by: Cédric Le Goater <address@hidden>

Since keyconfig was disabled in thunderbird, I have been adding
tags manually ...


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