linux-kernel - Re: [PATCH v10 5/7] x86/cpufeature: Detect CPUID faulting support

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Message-ID: <alpine.DEB.2.20.1611082002160.3501@nanos>
Date:   Tue, 8 Nov 2016 20:06:28 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Kyle Huey <me@...ehuey.com>
cc:     Robert O'Callahan <robert@...llahan.org>,
        Andy Lutomirski <luto@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Jeff Dike <jdike@...toit.com>,
        Richard Weinberger <richard@....at>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Shuah Khan <shuah@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Borislav Petkov <bp@...e.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Len Brown <len.brown@...el.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Dmitry Safonov <dsafonov@...tuozzo.com>,
        David Matlack <dmatlack@...gle.com>,
        linux-kernel@...r.kernel.org,
        user-mode-linux-devel@...ts.sourceforge.net,
        user-mode-linux-user@...ts.sourceforge.net,
        linux-fsdevel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        kvm@...r.kernel.org
Subject: Re: [PATCH v10 5/7] x86/cpufeature: Detect CPUID faulting support

On Tue, 8 Nov 2016, Kyle Huey wrote:

> Intel supports faulting on the CPUID instruction beginning with Ivy Bridge.
> When enabled, the processor will fault on attempts to execute the CPUID
> instruction with CPL>0. This will allow a ptracer to emulate the CPUID
> instruction.
> 
> Bit 31 of MSR_PLATFORM_INFO advertises support for this feature. It is
> documented in detail in Section 2.3.2 of
> http://www.intel.com/content/dam/www/public/us/en/documents/application-notes/virtualization-technology-flexmigration-application-note.pdf

Can you please stick that document into the kernel bugzilla, as it's going
to be on a different place before this gets merged into Linus tree?

See: http://lkml.kernel.org/r/1478631281-5061-1-git-send-email-kan.liang@intel.com

> +	static const struct msr_bit msr_bits[] = {
> +		{ X86_FEATURE_CPUID_FAULT,	MSR_PLATFORM_INFO, 31 },

Can you please make that PLATINFO_CPUID_FAULT_BIT instead of 31?

Thanks,

	tglx