Re: [Xen-devel] Xen hiding thermal capabilities from Dom0

[Jan Beulich <jbeulich@xxxxxxxx>]

On 21.11.2019 16:26, Rishi wrote:
> The affected Linux driver in my case is coretemp.ko (drivers/hwmon/coretemp.c)
> 
> It's init depends on checking presence of X86_FEATURE_DTHERM
> 
>         /*
>          * CPUID.06H.EAX[0] indicates whether the CPU has thermal
>          * sensors. We check this bit only, all the early CPUs
>          * without thermal sensors will be filtered out.
>          */
> 
> It seems to use below MSR
> MSR_IA32_PACKAGE_THERM_STATUS
> MSR_IA32_THERM_STATUS
> MSR_IA32_TEMPERATURE_TARGET
> 
> I'm not sure how can CPUID.06H.EAX[0] be read, should Xen provide a
> hypercall interface to read this?
> Even if a hypercall is given, coretemp will have to be modified to
> separate MSR calls.

A hypercall exists (XENPF_resource_op), and would just need
extension. It could e.g. permit access to said MSRs when
CPUID.06H.EAX[0] is 1. The coretemp driver would of course
need modification (or cloning).

Jan

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