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Subject: Re: [patch v2 1/2] x86,module: Detect VMX modules and disable
 Split-Lock-Detect
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        LKML <linux-kernel@vger.kernel.org>, x86@kernel.org,
        "Kenneth R. Crudup" <kenny@panix.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Jessica Yu <jeyu@kernel.org>,
        Fenghua Yu <fenghua.yu@intel.com>,
        Nadav Amit <namit@vmware.com>,
        Thomas Hellstrom <thellstrom@vmware.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Tony Luck <tony.luck@intel.com>,
        Steven Rostedt <rostedt@goodmis.org>
References: <20200402123258.895628824@linutronix.de>
 <20200402124205.242674296@linutronix.de>
 <20200402152340.GL20713@hirez.programming.kicks-ass.net>
 <725ca48f-8194-658e-0296-65d4368803b5@intel.com>
 <20200402162548.GH20730@hirez.programming.kicks-ass.net>
From:   Xiaoyao Li <xiaoyao.li@intel.com>
Message-ID: <2d2140c4-712a-2f8d-cde7-b3e64c28b204@intel.com>
Date:   Fri, 3 Apr 2020 00:41:57 +0800
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On 4/3/2020 12:25 AM, Peter Zijlstra wrote:
> 
> Learn to trim your replies already!

Sorry.

> 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.
> 
>> And, shouldn't we clear X86_FEATURE_SPLIT_LOCK_DETECT flag?
> 
> Don't think you can do that this late. Also, the hardware has the MSR
> and it works, it's just that we should not.
> 

Actually, I agree to keep this flag.

But, during the previous patch review, tglx wants to make

	sld_off = no X86_FEATURE_SPLIT_LOCK_DETECT

I'm not sure whether he still insists on it now.

I really want to decouple sld_off and X86_FEATURE_SPLIT_LOCK_DETECT.
So if X86_FEATURE_SPLIT_LOCK_DETECT is set, we can virtualize and expose 
it to guest even when host is sld_off.