Date: Wed, 31 Jan 2018 21:05:58 +0000 From: Steven Hartland <steven.hartland@multiplay.co.uk> To: rgrimes@freebsd.org Cc: "Bjoern A. Zeeb" <bzeeb-lists@lists.zabbadoz.net>, Konstantin Belousov <kostikbel@gmail.com>, 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: <CAHEMsqa=zGGxZ7%2Bus3wC2cG_85feshNuYXdCUS0qDjuxdg7jNA@mail.gmail.com> In-Reply-To: <201801311805.w0VI5DsU031265@pdx.rh.CN85.dnsmgr.net> References: <20180131164455.GR97752@kib.kiev.ua> <201801311805.w0VI5DsU031265@pdx.rh.CN85.dnsmgr.net>
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Pretty sure I=E2=80=99ve seen that too On Wed, 31 Jan 2018 at 18:05, Rodney W. Grimes < freebsd@pdx.rh.cn85.dnsmgr.net> wrote: > > 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 th= e > > > 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 Branc= h > > > Restricted Speculation (IBRS)???? > > Will do in half a hour. > > > -- > Rod Grimes > rgrimes@freebsd.org > >
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