linux-kernel - Re: [PATCH 2/3] x86/split_lock: Bits in IA32_CORE

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Message-ID: <87ftd1zzau.fsf@nanos.tec.linutronix.de>
Date:   Fri, 17 Apr 2020 21:29:13 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     "Luck\, Tony" <tony.luck@...el.com>
Cc:     Ingo Molnar <mingo@...nel.org>, Fenghua Yu <fenghua.yu@...el.com>,
        Borislav Petkov <bp@...en8.de>, H Peter Anvin <hpa@...or.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Andy Lutomirski <luto@...nel.org>,
        linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH 2/3] x86/split_lock: Bits in IA32_CORE_CAPABILITIES are not architectural

"Luck, Tony" <tony.luck@...el.com> writes:
> On Fri, Apr 17, 2020 at 12:04:36PM +0200, Thomas Gleixner wrote:
> +	if (!m->driver_data)
> +		goto setup;
> +	if (!cpu_has(c, X86_FEATURE_CORE_CAPABILITIES))
> +		return;
> +	rdmsrl(MSR_IA32_CORE_CAPS, ia32_core_caps);
> +	if (!(ia32_core_caps & MSR_IA32_CORE_CAPS_SPLIT_LOCK_DETECT))
> +		return;
> +setup:
> +	split_lock_setup();

Which looks nicer w/o the goto:

	if (m->driver_data) {
		if (!cpu_has(c, X86_FEATURE_CORE_CAPABILITIES))
			return;
		rdmsrl(MSR_IA32_CORE_CAPS, ia32_core_caps);
		if (!(ia32_core_caps & MSR_IA32_CORE_CAPS_SPLIT_LOCK_DETECT))
			return;
	}

Hmm?