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[Xen-devel] Re: expose MWAIT to dom0

To: "Tian, Kevin" <kevin.tian@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: [Xen-devel] Re: expose MWAIT to dom0
From: Keir Fraser <keir.xen@xxxxxxxxx>
Date: Mon, 15 Aug 2011 10:02:25 +0100
Cc: "Zhang, Yang Z" <yang.z.zhang@xxxxxxxxx>, "Wei, Gang" <gang.wei@xxxxxxxxx>
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On 15/08/2011 09:14, "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote:

>> cpu_has() accesses a pre-filled capabilities bitmask, filled from cpuid,
>> right? And cpuid goes through a pv_ops hook?
>> 
> 
> I'm not quite catching you here. Do you want to prefill mwait bit from pv_ops
> hook unconditionally even in current situation where Xen doesn't expose
> mwait, or selectively under some dom0's boot option even when Xen is
> changed to expose mwait? The first case is not sane, while for the 2nd case
> I don't think any pv_ops hook is required as long as Xen can expose it, isn't
> it?

But there is a pv_ops hook, and Xen isn't going to expose it because it
breaks old dom0 kernels.

 -- Keir



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