Re: [Xen-devel] [PATCH RFC] x86: Limit MSR_IA32_THERM_CONTROL and MSR_IA32_ENERGY_PERF_BIAS

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 18/12/2015 20:46, Konrad Rzeszutek Wilk wrote:
> Those two allow the OS pinned dom0 to change the T-state
> (throttling) behind the Xen cpufreq code.
>
> The patch that introduced this: f78e2193b6409577314167ed9e077de7ac3e652f
>
>     x86: Enable THERM_CONTROL_MSR write for dom0 even when cpufreq=xen
>
>     Signed-off-by: Wei Gang <gang.wei@xxxxxxxxx>
>     Signed-off-by: Keir Fraser <keir.fraser@xxxxxxxxxx>
>
> is very lacking on details.
>
> Anyhow this patch in effect reverts the above commit. It is also
> lacking in details :-)
>
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

We absolutely shouldn't let dom0 play with controls behind the back of a
driver in Xen.

It would be nice if we can find out some of the reasoning behind this
change, but I am in principle for it.

~Andrew

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