linux-kernel - Re: msr: Write to unrecognized MSR 0x38d by i7z

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Date:   Tue, 15 Sep 2020 14:14:33 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     peterz@...radead.org,
        Abhishek Jaiantilal <abhishek.jaiantilal@...orado.edu>,
        raininja <daniel.mclellan@...il.com>,
        Richard Hull <rm_hull@...oo.co.uk>
Cc:     Roman Stingler <roman.stingler@...varo.com>, x86@...nel.org,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: msr: Write to unrecognized MSR 0x38d by i7z

On Tue, Sep 15, 2020 at 01:10:12PM +0200, peterz@...radead.org wrote:
> On Tue, Sep 15, 2020 at 12:59:53PM +0200, Roman Stingler wrote:
> > Hi, when I open i7z I get following message in dmesg
> > 
> > [17548.541965] msr: Write to unrecognized MSR 0x38f by i7z
> >                Please report to x86@...nel.org
> > [17548.542030] msr: Write to unrecognized MSR 0x38d by i7z
> >                Please report to x86@...nel.org
> 
> That's PERF_GLOBAL_CTRL and PERF_FIXED_CTR_CTRL, userspace doesn't get
> to prod at those. Use the perf syscall.

Adding the authors/contributors of/to i7z.

Guys please consider converting your tool off of straight poking at MSRs
and to using proper kernel interfaces. If there are none for your use
case, feel free to define some and we'll help review them and get them
upstream. Poking at MSRs behind the kernel's back is a very very bad
idea.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette