linux-kernel - Re: [PATCH 4/4] x86/cpu: Use SERIALIZE in sync

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Message-ID: <20200727082344.GE119549@hirez.programming.kicks-ass.net>
Date:   Mon, 27 Jul 2020 10:23:44 +0200
From:   peterz@...radead.org
To:     Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...e.de>,
        Andy Lutomirski <luto@...nel.org>, x86@...nel.org,
        Dave Hansen <dave.hansen@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Cathy Zhang <cathy.zhang@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Kyung Min Park <kyung.min.park@...el.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        linux-kernel@...r.kernel.org,
        Ricardo Neri <ricardo.neri@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        linux-edac@...r.kernel.org
Subject: Re: [PATCH 4/4] x86/cpu: Use SERIALIZE in sync_core() when available

On Sun, Jul 26, 2020 at 09:31:32PM -0700, Ricardo Neri wrote:
> @@ -75,6 +77,12 @@ static inline void sync_core(void)
>  	 * Like all of Linux's memory ordering operations, this is a
>  	 * compiler barrier as well.
>  	 */
> +
> +	if (boot_cpu_has(X86_FEATURE_SERIALIZE)) {
> +		serialize();
> +		return;
> +	}
> +
>  	iret_to_self();

I was sorta expecting something like:

	alternative(IRET_TO_SELF, SERIALIZE, X86_FEATURE_SERIALIZE);

But instead you used boot_cpu_has() which is a dynamic test.