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Re: [PATCH] x86/rapl: Do not load in a guest

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* Peter Zijlstra <peterz@infradead.org> wrote:

> On Fri, Dec 04, 2015 at 08:42:06AM +0100, Ingo Molnar wrote:
> > 
> > * Borislav Petkov <bp@alien8.de> wrote:
> > 
> > > From: Borislav Petkov <bp@suse.de>
> > > 
> > > 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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[PATCH] x86/rapl: Do not load in a guest Borislav Petkov <bp@alien8.de> - 2015-12-03 19:30 +0100
  Re: [PATCH] x86/rapl: Do not load in a guest Jacob Pan <jacob.jun.pan@linux.intel.com> - 2015-12-03 19:40 +0100
    Re: [PATCH] x86/rapl: Do not load in a guest Borislav Petkov <bp@alien8.de> - 2015-12-03 19:50 +0100
      Re: [PATCH] x86/rapl: Do not load in a guest Jacob Pan <jacob.jun.pan@linux.intel.com> - 2015-12-03 20:10 +0100
        Re: [PATCH] x86/rapl: Do not load in a guest "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-12-04 00:10 +0100
          Re: [PATCH] x86/rapl: Do not load in a guest Borislav Petkov <bp@alien8.de> - 2015-12-04 00:30 +0100
            Re: [PATCH] x86/rapl: Do not load in a guest "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2015-12-04 01:40 +0100
  Re: [PATCH] x86/rapl: Do not load in a guest Ingo Molnar <mingo@kernel.org> - 2015-12-04 08:50 +0100
    Re: [PATCH] x86/rapl: Do not load in a guest Ingo Molnar <mingo@kernel.org> - 2015-12-04 09:30 +0100
      Re: [PATCH] x86/rapl: Do not load in a guest Borislav Petkov <bp@alien8.de> - 2015-12-04 11:30 +0100
        Re: [PATCH] x86/rapl: Do not load in a guest Paolo Bonzini <pbonzini@redhat.com> - 2015-12-04 11:50 +0100
          Re: [PATCH] x86/rapl: Do not load in a guest Borislav Petkov <bp@alien8.de> - 2015-12-04 12:00 +0100
            Re: [PATCH] x86/rapl: Do not load in a guest Ingo Molnar <mingo@kernel.org> - 2015-12-04 13:00 +0100
              Re: [PATCH] x86/rapl: Do not load in a guest Jacob Pan <jacob.jun.pan@linux.intel.com> - 2015-12-04 18:50 +0100
                Re: [PATCH] x86/rapl: Do not load in a guest Paolo Bonzini <pbonzini@redhat.com> - 2015-12-04 19:00 +0100
                Re: [PATCH] x86/rapl: Do not load in a guest Borislav Petkov <bp@alien8.de> - 2015-12-04 19:10 +0100
                Re: [PATCH] x86/rapl: Do not load in a guest Jacob Pan <jacob.jun.pan@linux.intel.com> - 2015-12-04 19:20 +0100
                Re: [PATCH] x86/rapl: Do not load in a guest Borislav Petkov <bp@alien8.de> - 2015-12-04 19:30 +0100
                Re: [PATCH] x86/rapl: Do not load in a guest Jacob Pan <jacob.jun.pan@linux.intel.com> - 2015-12-04 19:50 +0100
                Re: [PATCH] x86/rapl: Do not load in a guest Borislav Petkov <bp@alien8.de> - 2015-12-04 20:50 +0100
    Re: [PATCH] x86/rapl: Do not load in a guest Peter Zijlstra <peterz@infradead.org> - 2015-12-04 09:30 +0100
      Re: [PATCH] x86/rapl: Do not load in a guest Jacob Pan <jacob.jun.pan@linux.intel.com> - 2015-12-04 19:00 +0100
        Re: [PATCH] x86/rapl: Do not load in a guest Peter Zijlstra <peterz@infradead.org> - 2015-12-04 23:20 +0100
          Re: [PATCH] x86/rapl: Do not load in a guest "H. Peter Anvin" <hpa@zytor.com> - 2015-12-04 23:50 +0100

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