From owner-svn-src-head@freebsd.org Wed Jan 31 16:45:03 2018 Return-Path: Delivered-To: svn-src-head@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id D3893ED6223; Wed, 31 Jan 2018 16:45:03 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from kib.kiev.ua (kib.kiev.ua [IPv6:2001:470:d5e7:1::1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4AC046DCEA; Wed, 31 Jan 2018 16:45:03 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from tom.home (kib@localhost [127.0.0.1]) by kib.kiev.ua (8.15.2/8.15.2) with ESMTPS id w0VGitWK070158 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Wed, 31 Jan 2018 18:44:58 +0200 (EET) (envelope-from kostikbel@gmail.com) DKIM-Filter: OpenDKIM Filter v2.10.3 kib.kiev.ua w0VGitWK070158 Received: (from kostik@localhost) by tom.home (8.15.2/8.15.2/Submit) id w0VGittK070157; Wed, 31 Jan 2018 18:44:55 +0200 (EET) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: tom.home: kostik set sender to kostikbel@gmail.com using -f Date: Wed, 31 Jan 2018 18:44:55 +0200 From: Konstantin Belousov To: "Bjoern A. Zeeb" Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r328625 - in head/sys: amd64/amd64 amd64/ia32 amd64/include dev/cpuctl i386/i386 x86/include x86/x86 Message-ID: <20180131164455.GR97752@kib.kiev.ua> References: <201801311436.w0VEaRrZ030839@repo.freebsd.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.2 (2017-12-15) X-Spam-Status: No, score=-2.0 required=5.0 tests=ALL_TRUSTED,BAYES_00, DKIM_ADSP_CUSTOM_MED,FREEMAIL_FROM,NML_ADSP_CUSTOM_MED autolearn=no autolearn_force=no version=3.4.1 X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on tom.home X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 31 Jan 2018 16:45:04 -0000 On Wed, Jan 31, 2018 at 02:56:24PM +0000, Bjoern A. Zeeb wrote: > On 31 Jan 2018, at 14:36, Konstantin Belousov wrote: > > > Author: kib > > Date: Wed Jan 31 14:36:27 2018 > > New Revision: 328625 > > URL: https://svnweb.freebsd.org/changeset/base/328625 > > > > Log: > > IBRS support, AKA Spectre hardware mitigation. > > > For existing processors, you need a microcode update which adds IBRS > > CPU features, and to manually enable it by setting the > > tunable/sysctl > > hw.ibrs_disable to 0. Current status can be checked in sysctl > > hw.ibrs_active. The mitigation might be inactive if the CPU feature > > Can you change the tunable/sysctl to hw.ibrs_enable[d] (and toggle the > default setting along). This is done consistently with the hw.clflush_disable. Anyway, the intent is that the knob will be used for disabling, since defaults are going to be changed in the near future. > I find it highly confusing to have two different sysctls ???disable??? > and ???active??? and a lot > of people (and cultures) have trouble with the double negative. > Also the ???enable[d]??? variant seems to be pre-dominant in the kernel. > > Also can we spell IBRS in the sysctl description as ???Indirect Branch > Restricted Speculation (IBRS)???? Will do in half a hour.