linux-kernel - Re: [PATCH] PM / arch: x86: Rework the MSR_IA32_ENERGY_PERF

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Message-ID: <alpine.DEB.2.21.1904051731510.1802@nanos.tec.linutronix.de>
Date:   Fri, 5 Apr 2019 17:32:09 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
cc:     Peter Zijlstra <peterz@...radead.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>, x86 <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Len Brown <len.brown@...el.com>,
        Linux PM <linux-pm@...r.kernel.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Laura Abbott <labbott@...oraproject.org>,
        Ingo Molnar <mingo@...nel.org>,
        Simon Schricker <sschricker@...e.de>,
        Borislav Petkov <bp@...e.de>, Hannes Reinecke <hare@...e.de>
Subject: Re: [PATCH] PM / arch: x86: Rework the MSR_IA32_ENERGY_PERF_BIAS
 handling

On Thu, 21 Mar 2019, Rafael J. Wysocki wrote:

> On Thu, Mar 21, 2019 at 8:58 AM Peter Zijlstra <peterz@...radead.org> wrote:
> >
> > On Thu, Mar 21, 2019 at 01:00:52AM +0100, Rafael J. Wysocki wrote:
> > > + * The Performance and Energy Bias Hint (EPB) allows software to specify its
> > > + * preference with respect to the power-performance tradeoffs present in the
> > > + * processor.  Generally, the EPB is expected to be set by user space through
> > > + * the generic MSR interface (with the help of the x86_energy_perf_policy tool),
> > > + * but there are two reasons for the kernel to touch it.
> >
> > So I hate /dev/msr with a passion. It is absolute atrocious crap.
> >
> > Please, just make a real interface for this if it is important.
> 
> That's the plan going forward, this is just documenting the current situation.
> 
> Do you have any particular concerns regarding this patch?

No.

Acked-by: Thomas Gleixner <tglx@...utronix.de>