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

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Date:   Tue, 13 Sep 2016 11:42:33 -0700
From:   Kyle Huey <me@...ehuey.com>
To:     Borislav Petkov <bp@...e.de>
Cc:     "Robert O'Callahan" <robert@...llahan.org>,
        linux-api@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Len Brown <len.brown@...el.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Huang Rui <ray.huang@....com>,
        Aravind Gopalakrishnan <Aravind.Gopalakrishnan@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>,
        Andy Lutomirski <luto@...nel.org>,
        Juergen Gross <jgross@...e.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Jiri Slaby <jslaby@...e.cz>, Michal Hocko <mhocko@...e.com>,
        Alex Thorlton <athorlton@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Mateusz Guzik <mguzik@...hat.com>,
        Ben Segall <bsegall@...gle.com>,
        John Stultz <john.stultz@...aro.org>,
        "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" 
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] prctl,x86 Add PR_[GET|SET]_CPUID for controlling the
 CPUID instruction.

On Mon, Sep 12, 2016 at 7:15 AM, Kyle Huey <me@...ehuey.com> wrote:
> On Mon, Sep 12, 2016 at 2:07 AM, Borislav Petkov <bp@...e.de> wrote:
>> On Sun, Sep 11, 2016 at 05:29:23PM -0700, Kyle Huey wrote:
>>> @@ -2162,6 +2168,12 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
>>>       case PR_SET_TSC:
>>>               error = SET_TSC_CTL(arg2);
>>>               break;
>>> +     case PR_GET_CPUID:
>>> +             error = GET_CPUID_CTL(arg2);
>>> +             break;
>>> +     case PR_SET_CPUID:
>>> +             error = SET_CPUID_CTL(arg2);
>>> +             break;
>>>       case PR_TASK_PERF_EVENTS_DISABLE:
>>>               error = perf_event_task_disable();
>>>               break;
>>
>> This whole fun should be in arch_prctl() as it is arch-specific.
>
> Yeah, I was debating about that, and did it this way because of
> PR_SET_TSC.  Will fix.

arch_prctl is not yet exposed on 32 bit x86, so we'll have to add that
as well to do this.

- Kyle