linux-kernel - Re: [patch v2 1/2] x86,module: Detect VMX modules and disable Split-Lock-Detect

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Message-ID: <A86B173C-857C-4B7B-A543-BE967F9A1868@vmware.com>
Date:   Thu, 2 Apr 2020 16:39:11 +0000
From:   Nadav Amit <namit@...are.com>
To:     Peter Zijlstra <peterz@...radead.org>
CC:     Xiaoyao Li <xiaoyao.li@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>,
        "Kenneth R. Crudup" <kenny@...ix.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jessica Yu <jeyu@...nel.org>,
        Fenghua Yu <fenghua.yu@...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 v2 1/2] x86,module: Detect VMX modules and disable
 Split-Lock-Detect

> On Apr 2, 2020, at 9:25 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> 
> 
> Learn to trim your replies already!
> 
> On Fri, Apr 03, 2020 at 12:20:08AM +0800, Xiaoyao Li wrote:
>> On 4/2/2020 11:23 PM, Peter Zijlstra wrote:
> 
>>> +bad_module:
>>> +	pr_warn("disabled due to VMX in module: %s\n", me->name);
>>> +	sld_state = sld_off;
>> 
>> shouldn't we remove the __ro_after_init of sld_state?
> 
> Oh, that's probably a good idea. I can't actually test this due to no
> hardware.

Just wondering, since I lack hardware as well: can the performance counter
LOCK_CYCLES.SPLIT_LOCK_UC_LOCK_DURATION be used to detect split-locks
similarly to SLD (although it would be after the split-lock event)?