From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932652AbeBVNpR (ORCPT ); Thu, 22 Feb 2018 08:45:17 -0500 Received: from mx2.suse.de ([195.135.220.15]:48961 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932467AbeBVNpQ (ORCPT ); Thu, 22 Feb 2018 08:45:16 -0500 Date: Thu, 22 Feb 2018 14:44:58 +0100 From: Borislav Petkov To: "Raj, Ashok" Cc: X86 ML , LKML , Thomas Gleixner , Ingo Molnar , Tony Luck , Andi Kleen , Tom Lendacky , Arjan Van De Ven Subject: Re: [v2 1/3] x86/microcode/intel: Check microcode revision before updating sibling threads Message-ID: <20180222134259.GD27489@pd.tnic> References: <1519281205-58951-1-git-send-email-ashok.raj@intel.com> <1519281205-58951-2-git-send-email-ashok.raj@intel.com> <20180222110056.GA27489@pd.tnic> <20180222115554.GA3797@araj-mobl1.jf.intel.com> <20180222121506.GC27489@pd.tnic> <20180222131918.GB3797@araj-mobl1.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20180222131918.GB3797@araj-mobl1.jf.intel.com> User-Agent: Mutt/1.9.3 (2018-01-21) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 22, 2018 at 05:19:18AM -0800, Raj, Ashok wrote: > This isn't a simple WRMSR like others. Microcode engine needs to do > a bunch of validation. So this is slowly starting to resemble a real reason why not to. That should be part of the code comment. > We now have new guidance that the sibling must be spinning and not > doing other things that can introduce instability around loading > microcode. Why isn't *this* in the code comment? > I think its safer... That's not good enough - it should be: "It is not safe because... ". So that you can justify the overhead. -- Regards/Gruss, Boris. SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) --