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Re: [Qemu-ppc] [PATCH 4/4] spapr: Add support for time base offset migra

From: Alexey Kardashevskiy
Subject: Re: [Qemu-ppc] [PATCH 4/4] spapr: Add support for time base offset migration
Date: Sat, 12 Apr 2014 13:44:59 +1000
User-agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0

On 04/12/2014 07:55 AM, Benjamin Herrenschmidt wrote:
> On Fri, 2014-04-11 at 11:40 +0200, Alexander Graf wrote:
>>> And G5 uses 33333333. I really do not understand why it is bad to
>>> send-and-check timer frequency. Why?
>> Because the guest will continue to run at a different TB frequency on 
>> the new host and break.
> Right, which is why we should send it accross so it can be checked and
> we can barf accordingly rather than having random odd things happen :-)

As I was explained several times already, QEMU does not transfer
configuration (yet) and we only should implement correct transfer of
parameters (without checking) and specify in the QEMU command line the ones
which cannot be transferred.

So with timebase frequency, it should be a command line switch (-machine
option?) which would take frequency and fail if it is POWER7/8 and not
500MHz. And then libvirt should take care of it (always pass it or have XML
tag for it). Same story as with migrating IRQs (which I do now in a hacky
way but I am going to changed it to work via the command line).


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