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Re: [Xen-devel] Xen cpufreq support status: how to notify hypervisor of

To: "Matt T. Yourst" <yourst@xxxxxxxxxx>
Subject: Re: [Xen-devel] Xen cpufreq support status: how to notify hypervisor of frequency change?
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Mon, 10 Apr 2006 15:01:50 +0100
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On 8 Apr 2006, at 23:29, Matt T. Yourst wrote:

This appears to happen because virtual timer interrupts do not get delivered
on a regular basis for a few seconds following the frequency change.

Assuming we want to keep the cpufreq driver itself in dom0, what's the proper way to notify the hypervisor that the CPU frequency has just changed, so it can adjust its timers like the cpufreq driver on the native kernel does?

I'd really like to have cpufreq working properly under Xen (for both
workstations and to a lesser extent servers), so what would be the best way
to get this running?

The TSC needs recalibrating on the affected CPU. This will require adapting local_time_calibration() in arch/x86/time.c.

 -- Keir

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