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    SubjectRe: [PATCH] processor passthru - upload _Cx and _Pxx data to hypervisor (v5).
    >>> On 25.02.12 at 01:21, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> wrote:
    > But cpufreq != cpuidle != cpufreq governor, and they all are run by
    > different rules.
    > The ondemand cpufreq governor for example runs a timer and calls the
    > appropiate cpufreq
    > driver. So with these patches I posted we end up with a cpufreq driver in
    > the kernel
    > and in Xen hypervisor - both of them trying to change Pstates. Not good (to
    > be fair,
    > if powernow-k8/acpi-cpufreq would try it via WRMSR - those would up being
    > trapped and
    > ignored by the hypervisor. I am not sure about the outw though).

    I'm not aware of any trapping that would be done on the I/O port here;
    it could be added, though (i.e. the ports removed from the list of
    allowed ports of Dom0 once they become known to the hypervisor).

    > The pre-RFC version of this posted driver implemented a cpufreq governor that
    > was
    > nop and for future work was going to make a hypercall to get the true
    > cpufreq value
    > to report properly in /proc/cpuinfo - but I hadn't figured out a way to make
    > it be
    > the default one dynamically.
    >
    > Perhaps having xencommons do
    > echo "xen" > /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
    >
    > And s/processor-passthru/cpufreq-xen/ would do it? That would eliminate the
    > [performance,
    > ondemand,powersave,etc] cpufreq governors from calling into the cpufreq
    > drivers to alter P-states.

    Except that you want this to be a cpufreq driver, not a governor.

    Jan



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