From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753357AbaIYOky (ORCPT ); Thu, 25 Sep 2014 10:40:54 -0400 Received: from out3-smtp.messagingengine.com ([66.111.4.27]:35089 "EHLO out3-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753075AbaIYOkj (ORCPT ); Thu, 25 Sep 2014 10:40:39 -0400 X-Sasl-enc: +xkv/fUVTRPOZhREnroRN/b7YUb4oVXRxNtOgZURrN+5 1411656037 Date: Thu, 25 Sep 2014 11:40:25 -0300 From: Henrique de Moraes Holschuh To: Borislav Petkov Cc: Chuck Ebbert , Andy Lutomirski , "H. Peter Anvin" , "linux-kernel@vger.kernel.org" Subject: Re: x86, microcode: BUG: microcode update that changes x86_capability Message-ID: <20140925144025.GA14030@khazad-dum.debian.net> References: <20140919110014.GC29639@khazad-dum.debian.net> <20140919112953.GA3256@nazgul.tnic> <20140919075415.5149d5f2@as> <20140919150042.GC5318@nazgul.tnic> <20140919164217.GD17456@khazad-dum.debian.net> <20140923200054.GB16467@pd.tnic> <20140924145658.GB31678@khazad-dum.debian.net> <20140925085158.GF22317@nazgul.tnic> <20140925113643.GB10569@khazad-dum.debian.net> <20140925121007.GA25334@nazgul.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140925121007.GA25334@nazgul.tnic> X-GPG-Fingerprint1: 4096R/39CB4807 C467 A717 507B BAFE D3C1 6092 0BD9 E811 39CB 4807 X-GPG-Fingerprint2: 1024D/1CDB0FE3 5422 5C61 F6B7 06FB 7E04 3738 EE25 DE3F 1CDB 0FE3 User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 25 Sep 2014, Borislav Petkov wrote: > On Thu, Sep 25, 2014 at 08:36:45AM -0300, Henrique de Moraes Holschuh wrote: > > This isn't an useless fix, it will allow systems without early initramfs > > support to operate correctly after a microcode update. > > So what do we do if we update the microcode late and some userspace task > is using HLE and all of a sudden it segfaults and gets killed due to > #UD. I'll forward all those complaint emails to you then, no? > > :-) > > What's saying is, a reboot in this case is maybe the lesser of two evils. In that case we should blacklist to refuse to apply the update, and reboot only if the blacklist wasn't good enough and we detect that something really important in the cpu feature cpuid bits changed. However, a reboot is even worse than everything linked to libpthread segfaulting, as it will also cause data loss for the stuff that didn't get SIGILL'd to death. Meh. Backporting early initramfs support to 3.0/3.2/3.4 doesn't seem doable, or wise. At this point, what alternatives are left? -- "One disk to rule them all, One disk to find them. One disk to bring them all and in the darkness grind them. In the Land of Redmond where the shadows lie." -- The Silicon Valley Tarot Henrique Holschuh