linux-kernel - Re: [PATCH 01/16] x86/intel: Initialize IA32_FEATURE

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

Message-ID: <afd37a28-d135-7c34-bd63-7c11099998bc@redhat.com>
Date:   Mon, 7 Oct 2019 19:05:32 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Tony Luck <tony.luck@...el.com>,
        Tony W Wang-oc <TonyWWang-oc@...oxin.com>
Cc:     "H. Peter Anvin" <hpa@...or.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, linux-edac@...r.kernel.org,
        Borislav Petkov <bp@...e.de>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Subject: Re: [PATCH 01/16] x86/intel: Initialize IA32_FEATURE_CONTROL MSR at
 boot

On 04/10/19 23:56, Sean Christopherson wrote:
> Always lock IA32_FEATURE_CONTROL if it exists, even if the CPU doesn't
> support VMX, so that other existing and future kernel code that queries
> IA32_FEATURE_CONTROL can assume it's locked.

Possibly stupid question: why bother locking it?  It makes sense to lock
the MSR bits to _off_ in the firmware, but if the BIOS hasn't locked it,
why should the OS?

It seems to me that locking introduces a lot of complication.

Paolo