linux-kernel - Re: [PATCH v7 6/6] x86/arch_prctl: Add ARCH_[GET|SET]

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <alpine.DEB.2.20.1610280038260.4913@nanos>
Date:   Fri, 28 Oct 2016 00:38:54 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Andy Lutomirski <luto@...capital.net>
cc:     Kyle Huey <me@...ehuey.com>,
        Robert O'Callahan <robert@...llahan.org>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
        Jeff Dike <jdike@...toit.com>,
        Richard Weinberger <richard@....at>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...e.de>,
        Dmitry Safonov <dsafonov@...tuozzo.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Shuah Khan <shuah@...nel.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Len Brown <len.brown@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "user-mode-linux-devel@...ts.sourceforge.net" 
        <user-mode-linux-devel@...ts.sourceforge.net>,
        "open list:USER-MODE LINUX (UML)" 
        <user-mode-linux-user@...ts.sourceforge.net>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>
Subject: Re: [PATCH v7 6/6] x86/arch_prctl: Add ARCH_[GET|SET]_CPUID

On Thu, 27 Oct 2016, Andy Lutomirski wrote:
> On Thu, Oct 27, 2016 at 4:15 AM, Thomas Gleixner <tglx@...utronix.de> wrote:
> Let's just do this right from day one:
> 
> static void set_cpuid_faulting(bool on)
> {
>   u64 msrval;
> 
>   DEBUG_LOCKS_WARN_ON(!irqs_disabled());
> 
>   msrval = this_cpu_read(msr_misc_features_enables_shadow);
>   msrval &= CPUID_FAULT_ENABLE;
>   msrval |= (on << CPUID_FAULT_ENABLE_BIT);
>   this_cpu_write(msr_misc_features_enables_shadow, msrval);
>   wrmsrl(MSR_MISC_FEATURES_ENABLES, msrval);
> }
> 
> RDMSR may be considerably faster than WRMSR, but that doesn't mean it's *fast*.

Good point!