linux-kernel - Re: [patch 1/2] x86,module: Detect VMX modules and disable Split-Lock-Detect

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Message-ID: <bc9a0c9a-7bd0-c85d-4795-ae0b4faa5e84@prevas.dk>
Date:   Fri, 3 Apr 2020 01:42:33 +0200
From:   Rasmus Villemoes <rasmus.villemoes@...vas.dk>
To:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, "Kenneth R. Crudup" <kenny@...ix.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jessica Yu <jeyu@...nel.org>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Xiaoyao Li <xiaoyao.li@...el.com>,
        Nadav Amit <namit@...are.com>,
        Thomas Hellstrom <thellstrom@...are.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [patch 1/2] x86,module: Detect VMX modules and disable
 Split-Lock-Detect

On 02/04/2020 14.32, Thomas Gleixner wrote:
> From: Peter Zijlstra <peterz@...radead.org>
> 
> It turns out that with Split-Lock-Detect enabled (default) any VMX
> hypervisor needs at least a little modification in order to not blindly
> inject the #AC into the guest without the guest being ready for it.
> 
> Since there is no telling which module implements a hypervisor, scan the
> module text and look for the VMLAUNCH instruction. If found, the module is
> assumed to be a hypervisor of some sort and SLD is disabled.

How long does that scan take/add to module load time? Would it make
sense to exempt in-tree modules?

Rasmus