From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756705AbaISPAx (ORCPT ); Fri, 19 Sep 2014 11:00:53 -0400 Received: from mail.skyhub.de ([78.46.96.112]:39087 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754085AbaISPAv (ORCPT ); Fri, 19 Sep 2014 11:00:51 -0400 Date: Fri, 19 Sep 2014 17:00:42 +0200 From: Borislav Petkov To: Chuck Ebbert Cc: Henrique de Moraes Holschuh , Andy Lutomirski , "H. Peter Anvin" , "linux-kernel@vger.kernel.org" Subject: Re: x86, microcode: BUG: microcode update that changes x86_capability Message-ID: <20140919150042.GC5318@nazgul.tnic> References: <20140918135202.GA26038@khazad-dum.debian.net> <541B2F33.8000002@amacapital.net> <20140918145328.0253f009@as> <9c84cde6-3d70-4337-8738-0283d06d8cf0@email.android.com> <20140918200659.GA5331@khazad-dum.debian.net> <20140919001311.GB5331@khazad-dum.debian.net> <20140919110014.GC29639@khazad-dum.debian.net> <20140919112953.GA3256@nazgul.tnic> <20140919075415.5149d5f2@as> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20140919075415.5149d5f2@as> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 19, 2014 at 07:54:14AM -0500, Chuck Ebbert wrote: > Assuming we can identify all the affected models and steppings, maybe > something like this would work: > > 1) Refuse to finish booting if a microcode update that disables TSX > isn't applied before userspace starts running on those CPUs. Well, I think when we're booting, we would have already applied the early microcode, no? Because then it is a non-issue. > 2) Don't allow a late update if TSX is still enabled on those > processors. Yeah, so the use case I have in mind is when a long-running machine wants to apply microcode and this microcode disables CPUID bits and instructions. And the machine cannot be rebooted. I guess in that case we would have to issue a warning only on the affected processors that a rebooted is mandatory and fail the update... Maybe something like that. > (1) could be overridden by a command line option for people who want > to develop TSX code. The way I understand it, those people shouldn't apply the microcode patch at all. -- Regards/Gruss, Boris. --