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[Xen-devel] Re: TSC scaling and softtsc reprise, and PROPOSAL

To: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, "Zhang, Xiantao" <xiantao.zhang@xxxxxxxxx>, Ian Pratt <Ian.Pratt@xxxxxxxxxxxxx>, "Xen-Devel (E-mail)" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: [Xen-devel] Re: TSC scaling and softtsc reprise, and PROPOSAL
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Tue, 28 Jul 2009 19:43:11 +0100
Cc: "Dong, Eddie" <eddie.dong@xxxxxxxxx>, John Levon <levon@xxxxxxxxxxxxxxxxx>
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On 28/07/2009 19:15, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx> wrote:

>> I can live with that, if it is driven from the xend
>> toolstack. It will have
>> to default off in the hypervisor for compatibility with old
>> saved images.
> Hmmm... one could argue that with the current model,
> any VM using TSC is "at your own peril" and there are
> certainly cases of restore that will break whatever
> assumptions the VM is making about pre-save TSC
> values.   So while I'm a believer in compatibility,
> I'd suggest default ON in the hypervisor and
> a new restore option that force-overrides the
> softtsc boot-time default for any VM being restored.

It would be defaulted on by the toolstack for all newly created guests.
That's quite sufficient I think.

 -- Keir

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