* Peter Zijlstra <[email protected]> wrote:
> On Fri, Dec 04, 2015 at 08:42:06AM +0100, Ingo Molnar wrote:
> >
> > * Borislav Petkov <[email protected]> wrote:
> >
> > > From: Borislav Petkov <[email protected]>
> > >
> > > qemu/kvm doesn't support RAPL and RAPL doesn't have a CPUID feature bit
> > > so check whether we're in a guest instead.
> >
> > So when a hypervisor starts supporting RAPL we'll disable the driver
> > erroneously?
> >
> > Isn't there any better method to detect RAPL support?
> >
> > So in particular in drivers/powercap/intel_rapl.c there's an enumerated
> > list of
> > CPU models, which is used via a x86_match_cpu() call. That's still not
> > ideal (it
> > does not work on hypervisors for example), but even better would be to
> > detect RAPL
> > support in some other fashion, that does not rely on us statically
> > enumerating CPU
> > models that support it.
>
> RAPL isn't enumerated, the best we could do is attempt to write to one
> of the writable MSRs and see if that 'works'.
Hm, bad - writing to MSRs like that is generally dangerous.
So we should at least provide a central 'is RAPL available' call instead of
spreading multiple X86_FEATURE_HYPERVISOR checks.
Thanks,
Ingo
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