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RE: [Xen-devel] [RFC] Physical hot-add cpus and TSC

To: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, Keir Fraser <Keir.Fraser@xxxxxxxxxxxxx>, "Xen-Devel (xen-devel@xxxxxxxxxxxxxxxxxxx)" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] [RFC] Physical hot-add cpus and TSC
From: Ian Pratt <Ian.Pratt@xxxxxxxxxxxxx>
Date: Wed, 26 May 2010 18:02:16 +0100
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Thread-topic: [Xen-devel] [RFC] Physical hot-add cpus and TSC
> Possibly... but the code for whacking the TSC of a CPU after
> C3-state results in a TSC value that is poorly-aligned with other
> running TSCs.  If there is a better way for "whacking" that
> results in a nearly-perfectly-aligned TSC (that would pass
> a "tsc warp test"), that is an option.

It ought to be possible to enhance the "whacking" code to set the TSC based on 
the topologically nearest live CPU and then sanity-check against all others, 
repeating a few times to protect against SMIs etc.  


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