linux-kernel - Re: [PATCH v5 1/9] x86/split_lock: Rework the initialization flow of split lock detection

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Date:   Wed, 25 Mar 2020 01:52:58 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Xiaoyao Li <xiaoyao.li@...el.com>, Ingo Molnar <mingo@...hat.com>,
        Borislav Petkov <bp@...en8.de>, hpa@...or.com,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        kvm@...r.kernel.org, x86@...nel.org, linux-kernel@...r.kernel.org
Cc:     Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Jim Mattson <jmattson@...gle.com>
Subject: Re: [PATCH v5 1/9] x86/split_lock: Rework the initialization flow of split lock detection

Xiaoyao Li <xiaoyao.li@...el.com> writes:
> On 3/24/2020 6:29 PM, Thomas Gleixner wrote:
>> -	switch (sld_state) {
>> +	switch (state) {
>>   	case sld_off:
>>   		pr_info("disabled\n");
>> -		break;
>> -
>> +		return;
> Here, when sld_off, it just returns without 
> setup_force_cpu_cap(X86_FEATURE_SPLIT_LOCK_DETECT).
>
> So for APs, it won't clear SLD bit in split_lock_init().

Trivial fix:

static void split_lock_init(void)
{
	split_lock_verify_msr(sld_state != sld_off);
}

You just need to remove the __init annotation from split_lock_verify_msr().

Thanks,

        tglx