From owner-svn-src-all@freebsd.org Wed Jan 31 18:05:18 2018 Return-Path: Delivered-To: svn-src-all@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 895A7EDA011; Wed, 31 Jan 2018 18:05:18 +0000 (UTC) (envelope-from freebsd@pdx.rh.CN85.dnsmgr.net) Received: from pdx.rh.CN85.dnsmgr.net (br1.CN84in.dnsmgr.net [69.59.192.140]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 1179971706; Wed, 31 Jan 2018 18:05:17 +0000 (UTC) (envelope-from freebsd@pdx.rh.CN85.dnsmgr.net) Received: from pdx.rh.CN85.dnsmgr.net (localhost [127.0.0.1]) by pdx.rh.CN85.dnsmgr.net (8.13.3/8.13.3) with ESMTP id w0VI5DKm031266; Wed, 31 Jan 2018 10:05:13 -0800 (PST) (envelope-from freebsd@pdx.rh.CN85.dnsmgr.net) Received: (from freebsd@localhost) by pdx.rh.CN85.dnsmgr.net (8.13.3/8.13.3/Submit) id w0VI5DsU031265; Wed, 31 Jan 2018 10:05:13 -0800 (PST) (envelope-from freebsd) From: "Rodney W. Grimes" Message-Id: <201801311805.w0VI5DsU031265@pdx.rh.CN85.dnsmgr.net> Subject: Re: svn commit: r328625 - in head/sys: amd64/amd64 amd64/ia32 amd64/include dev/cpuctl i386/i386 x86/include x86/x86 In-Reply-To: <20180131164455.GR97752@kib.kiev.ua> To: Konstantin Belousov Date: Wed, 31 Jan 2018 10:05:13 -0800 (PST) CC: "Bjoern A. Zeeb" , src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Reply-To: rgrimes@freebsd.org X-Mailer: ELM [version 2.4ME+ PL121h (25)] MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=US-ASCII X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 31 Jan 2018 18:05:18 -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 thought we had something some place that said negative assertions should be avoided if possible. > > 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. -- Rod Grimes rgrimes@freebsd.org