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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <alpine.DEB.2.21.1811081216460.1549@nanos.tec.linutronix.de>
Date:   Thu, 8 Nov 2018 12:18:23 +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 Wed, 7 Nov 2018, Tim Chen wrote:
> On 11/03/2018 11:29 AM, Thomas Gleixner wrote:
> > 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.
> > 
> 
> Should I just drop this patch then and only replace
> sched_smt_present with cpu_smt_enabled?

You have to decide which of the exports to drop. No strong opinion.

Thanks,

	tglx