linux-kernel - Re: [Patch v4 07/18] x86/smt: Convert cpu_smt_control check to cpu_smt

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Message-ID: <alpine.DEB.2.21.1811031928010.3160@nanos.tec.linutronix.de>
Date:   Sat, 3 Nov 2018 19:29:52 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Tim Chen <tim.c.chen@...ux.intel.com>
cc:     Jiri Kosina <jikos@...nel.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Casey Schaufler <casey.schaufler@...el.com>,
        Asit Mallick <asit.k.mallick@...el.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Jon Masters <jcm@...hat.com>,
        Waiman Long <longman9394@...il.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [Patch v4 07/18] x86/smt: Convert cpu_smt_control check to
 cpu_smt_enabled static key

Tim,

On Tue, 30 Oct 2018, Tim Chen wrote:

> Change the SMT code paths check from using cpu_smt_control to
> cpu_smt_enabled static key.  This saves a branching check.

and adds extra size to the kernel for the patching. The only reason why it
would make sense for kvm is that then the EXPORT of cpu_smt_control can go
away, which takes more space than the patch data.

Thanks,

	tglx