linux-kernel - Re: [PATCH] prctl,x86 Add PR_[GET|SET]_CPUID for controlling the CPUID instruction.

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Message-ID: <20160912171828.gztxu5bgbmjcd4mt@pd.tnic>
Date:   Mon, 12 Sep 2016 19:18:28 +0200
From:   Borislav Petkov <bp@...e.de>
To:     Andy Lutomirski <luto@...capital.net>
Cc:     Kyle Huey <me@...ehuey.com>, Thomas Gleixner <tglx@...utronix.de>,
        John Stultz <john.stultz@...aro.org>,
        Ingo Molnar <mingo@...hat.com>, Michal Hocko <mhocko@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Aravind Gopalakrishnan <Aravind.Gopalakrishnan@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Mateusz Guzik <mguzik@...hat.com>,
        Alex Thorlton <athorlton@....com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>,
        Jiri Slaby <jslaby@...e.cz>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Ben Segall <bsegall@...gle.com>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Robert O'Callahan <robert@...llahan.org>,
        "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" 
        <linux-kernel@...r.kernel.org>, Juergen Gross <jgross@...e.com>,
        Linux API <linux-api@...r.kernel.org>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Kees Cook <keescook@...omium.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Len Brown <len.brown@...el.com>, Huang Rui <ray.huang@....com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] prctl,x86 Add PR_[GET|SET]_CPUID for controlling the
 CPUID instruction.

On Mon, Sep 12, 2016 at 09:56:11AM -0700, Andy Lutomirski wrote:
> This should have a cpufeature bit and show up in /proc/cpuinfo.  That

Haha, test a cpufeature with a faulting CPUID :-)

Yeah, we need a synthetic flag and query MSR_PLATFORM_INFO[31] which
denotes whether the other MSR - MISC_FEATURES_ENABLES - is there and bit
0 is defined.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--