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xen-devel
Re: [Xen-devel] cpufreq support status
>>> Keir Fraser <Keir.Fraser@xxxxxxxxxxxx> 17.10.07 16:34 >>>
>On 17/10/07 15:20, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote:
>
>> The question is whether *any* of the cpufreq drivers will now work (with
>> Xen properly adjusting to the changed frequency) versus whether this
>> now can only be expected to work for powernow-k8 (plus perhaps
>> acpi-cpufreq). In the latter case I'd likely continue to have the
>> CPU_FREQ selector depend on !XEN in our kernels, instead of the
>> more fragile disabling of individual drivers...
>>
>> The cpufreq notifier would suggest it's generic, but the MSR accesses
>> needed by other drivers would suggest it's not.
>
>It's definitely k8-powernow only right now. acpi-cpufreq might work if the
>control register is an i/o port. It won't work if the control register is an
>MSR, since the MSR would not be whitelisted in the WRMSR emulation in
>emulate_privileged_op().
Does ACPI have means to specify MSRs as the access mechanism? I don't
recall platform specific behavior like this, I thought this was restricted to
the set of types named ACPI_ADR_SPACE_* in Linux' include/acpi/actypes.h
(and which already goes beyond what is in ACPI 3.0b).
Jan
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