linux-kernel - Re: [patch 0/2] x86: Prevent Split-Lock-Detection wreckage on VMX hypervisors

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Message-ID: <D07135B9-576F-4232-8A1B-BEC5D26F35B8@vmware.com>
Date:   Thu, 2 Apr 2020 14:47:33 +0000
From:   Nadav Amit <namit@...are.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>
CC:     "Kenneth R. Crudup" <kenny@...ix.com>,
        LKML <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jessica Yu <jeyu@...nel.org>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Xiaoyao Li <xiaoyao.li@...el.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 0/2] x86: Prevent Split-Lock-Detection wreckage on VMX
 hypervisors

> On Apr 2, 2020, at 7:37 AM, Thomas Gleixner <tglx@...utronix.de> wrote:
> 
> "Kenneth R. Crudup" <kenny@...ix.com> writes:
> 
>> On Thu, 2 Apr 2020, Thomas Gleixner wrote:
>> 
>>> As Peter and myself don't have access to a SLD enabled machine, the
>>> KVM/VMX part is untested. The module scan part works.
>> 
>> I just applied both of these patches to my (Linus' tip) tree, and unfortunately
>> VMWare still hangs if split_lock_detect= is set to anything but "off".
>> 
>> Was there anything else I'd needed to do?
> 
> Hmm. Not really. Does dmesg show the warning when the VMWare module loads?
> Something like:
> 
>  x86/split lock detection: disabled due to VMLAUNCH in module: ….

I ran an objdump on VMware workstation and indeed I do not see a
VMLAUNCH/VMRESUME. I do see however VMXON which should also be good for
detecting hypervisors. I will try to understand why VMLAUNCH is not there.