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

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Date:	Fri, 4 Dec 2015 08:42:06 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Borislav Petkov <bp@...en8.de>, Amy Wiles <amy.l.wiles@...el.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
	Jacob Pan <jacob.jun.pan@...ux.intel.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] x86/rapl: Do not load in a guest

* Borislav Petkov <bp@...en8.de> wrote:

> From: Borislav Petkov <bp@...e.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.

Thanks,

	Ingo
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