linux-kernel - Re: [PATCH v2] tools/power turbostat: Fix RAPL summary collection on AMD processors

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Message-ID: <YILZ1aNVrAa9vx79@zn.tnic>
Date:   Fri, 23 Apr 2021 16:29:41 +0200
From:   Borislav Petkov <bp@...e.de>
To:     Calvin Walton <calvin.walton@...stin.ca>
Cc:     Chen Yu <yu.c.chen@...el.com>, Terry Bowman <terry.bowman@....com>,
        lenb@...nel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, wei.huang2@....com, aros@....com,
        rui.zhang@...el.com
Subject: Re: [PATCH v2] tools/power turbostat: Fix RAPL summary collection on
 AMD processors

On Fri, Apr 23, 2021 at 10:00:14AM -0400, Calvin Walton wrote:
> So, there's two problems with that:
>    1. This function needs to be able to return an error value that cannot be
>       confused with a valid MSR. This is currently done by returning a
>       negative number. If an unsigned value is used, a different way of
>       indicating errors needs to be written.
>    2. We are not using CPU instructions to access MSRs direction. Instead
>       they are being read from /dev/msr. So the "offset" value is actually a
>       seek into the /dev/msr file (using pread), and thus is of type off_t.

Ah right, that's the /dev/msr thing. Then off_t is correct, forget what
I said.

Thx.

-- 
Regards/Gruss,
    Boris.

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