linux-kernel - Re: [PATCH v5 3/3] perf x86: Exposing an Uncore unit to PMON for Intel Xeon® server platform

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Message-ID: <20200211185759.GA1941673@kroah.com>
Date:   Tue, 11 Feb 2020 10:57:59 -0800
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Andi Kleen <ak@...ux.intel.com>
Cc:     roman.sudarikov@...ux.intel.com, peterz@...radead.org,
        mingo@...hat.com, acme@...nel.org, mark.rutland@....com,
        alexander.shishkin@...ux.intel.com, jolsa@...hat.com,
        namhyung@...nel.org, linux-kernel@...r.kernel.org,
        eranian@...gle.com, bgregg@...flix.com, kan.liang@...ux.intel.com,
        alexander.antonov@...el.com
Subject: Re: [PATCH v5 3/3] perf x86: Exposing an Uncore unit to PMON for Intel Xeon® server platform

On Tue, Feb 11, 2020 at 10:42:00AM -0800, Andi Kleen wrote:
> On Tue, Feb 11, 2020 at 09:15:44AM -0800, Greg KH wrote:
> > On Tue, Feb 11, 2020 at 07:15:49PM +0300, roman.sudarikov@...ux.intel.com wrote:
> > > +static ssize_t skx_iio_mapping_show(struct device *dev,
> > > +				struct device_attribute *attr, char *buf)
> > > +{
> > > +	struct pmu *pmu = dev_get_drvdata(dev);
> > > +	struct intel_uncore_pmu *uncore_pmu =
> > > +		container_of(pmu, struct intel_uncore_pmu, pmu);
> > > +
> > > +	struct dev_ext_attribute *ea =
> > > +		container_of(attr, struct dev_ext_attribute, attr);
> > > +	long die = (long)ea->var;
> > > +
> > > +	return sprintf(buf, "0000:%02x\n", skx_iio_stack(uncore_pmu, die));
> > 
> > If "0000:" is always the "prefix" of the output of this file, why have
> > it at all as you always know it is there?
> > 
> > What is ever going to cause that to change?
> 
> I think it's just to make it a complete PCI address.

Is that what this really is?  If so, it's not a "complete" pci address,
is it?  If it is, use the real pci address please.

> In theory it might be different on a complex multi node system with
> custom interconnect and multiple PCI segments, but that would need code
> changes too.
> 
> This version of the patchkit only supports standard SKX systems
> at this point.

I have no idea what that means, please translate for non-Intel people :)

greg k-h