linux-kernel - Re: [PATCH 2/2] tools/power/x86/intel-speed-select: Display core count for bucket

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Message-ID: <b8c7bd1204f7b4f75a5bccec4d7c41b1225928f7.camel@linux.intel.com>
Date:   Fri, 06 Sep 2019 08:07:29 -0700
From:   Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
To:     Andy Shevchenko <andriy.shevchenko@...el.com>,
        Prarit Bhargava <prarit@...hat.com>
Cc:     darcari@...hat.com, linux-kernel@...r.kernel.org,
        platform-driver-x86@...r.kernel.org
Subject: Re: [PATCH 2/2] tools/power/x86/intel-speed-select: Display core
 count for bucket

On Fri, 2019-09-06 at 07:50 -0700, Srinivas Pandruvada wrote:
> On Fri, 2019-09-06 at 16:46 +0300, Andy Shevchenko wrote:
> > On Fri, Sep 06, 2019 at 05:39:54AM -0400, Prarit Bhargava wrote:
> > > On 9/5/19 7:37 PM, Srinivas Pandruvada wrote:
> > > > Read the bucket and core count relationship via MSR and display
> > > > when displaying turbo ratio limits.
> > > > +	ret = isst_send_msr_command(cpu, 0x1ae, 0,
> > > > buckets_info);
> > > 
> > > ^^^ you can get rid of the magic number 0x1ae by doing (sorry for
> > > the cut-and-paste)
> > > 
> > > diff --git a/tools/power/x86/intel-speed-select/Makefile
> > > b/tools/power/x86/intel
> > > index 12c6939dca2a..087d802ad844 100644
> > > --- a/tools/power/x86/intel-speed-select/Makefile
> > > +++ b/tools/power/x86/intel-speed-select/Makefile
> > > @@ -15,6 +15,8 @@ endif
> > >  MAKEFLAGS += -r
> > > 
> > >  override CFLAGS += -O2 -Wall -g -D_GNU_SOURCE -I$(OUTPUT)include
> > > +override CFLAGS += -I../../../include
> > > +override CFLAGS +=
> > > -DMSRHEADER='"../../../../arch/x86/include/asm/msr-index.h"'
> 
> No, we can't use msr_index.
This comment was meant for use of /dev/cpu/X/msr not msr_index.
I didn't want to bring in dependency on msr-index.h for couple of 2
MSRs and the names in msr-index.h doesn't really reflect the actual
processing, they are doing. For example MSR_TURBO_RATIO_LIMIT1 for
0x1ae. The definition of 0x1AE is different on cpu model 0x55 and
beyond.

> 
> > 
> > I guess it can be done in more neat way.
> > 
> > > As I've been looking at this code I have been wondering why
> > > didn't
> > > you just use
> > > the standard /dev/cpu/X/msr interface that other x86 power
> > > utilities (turbostat,
> > > x86_energy_perf_policy) use?  Implementing msr_read() is trivial
> > > (warning
> > > untested and uncompiled code)
> 
> No. We can't. The MSR interface is disabled on several distribution
> and
> platforms with secured boot. So some special MSRs are only allowed
> via
> this IOCTL interface.
> 
> Thanks,
> Srinivas
> 
> 
> > 
> > Actually good point!
> >