linux-kernel - Re: [PATCH v6 4/8] kvm: x86: Emulate split-lock access as a write in emulator

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Message-ID: <87lfnpz4k2.fsf@nanos.tec.linutronix.de>
Date:   Wed, 25 Mar 2020 01:00:45 +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>
Cc:     x86@...nel.org, kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        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>,
        Xiaoyao Li <xiaoyao.li@...el.com>
Subject: Re: [PATCH v6 4/8] kvm: x86: Emulate split-lock access as a write in emulator

Xiaoyao Li <xiaoyao.li@...el.com> writes:
>  
> +bool split_lock_detect_on(void)
> +{
> +	return sld_state != sld_off;
> +}
> +EXPORT_SYMBOL_GPL(split_lock_detect_on);

1) You export this function here

2) You change that in one of the next patches to something else

3) According to patch 1/8 X86_FEATURE_SPLIT_LOCK_DETECT is not set when
   sld_state == sld_off. FYI, I did that on purpose.

AFAICT #1 and #2 are just historical leftovers of your previous patch
series and the extra step was just adding more changed lines per patch
for no value.

#3 changed the detection mechanism and at the same time the semantics of
the feature flag.

So what's the point of this exercise? 

Thanks,

        tglx