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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: Tue, 11 Apr 2006 09:25:16 +0100
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On 11 Apr 2006, at 01:05, Matt T. Yourst wrote:

Note that I only implemented this for powernow-k8 right now, since that's the only hardware I could test it on. It's very obvious how to adapt it to the other cpufreq drivers, by just replacing rdmsr and wrmsr with the Xen wrapper
versions I provided, and adding in the setcpufreq hypercall at the end.

All this stuff should be done by emulating the MSR writes in emulate_privileged_op() in arch/x86/traps.c. This will avoid any modification of Linux at all. Currently there's only simple filtering of MSR write attempts, but picking up on cpu-freq MSR accesses on e.g., AMD systems and also resync'ing the local clock would not be difficult.

 -- Keir

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