From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754810AbcAHMQG (ORCPT ); Fri, 8 Jan 2016 07:16:06 -0500 Received: from ud10.udmedia.de ([194.117.254.50]:32829 "EHLO mail.ud10.udmedia.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754505AbcAHMQE (ORCPT ); Fri, 8 Jan 2016 07:16:04 -0500 Date: Fri, 8 Jan 2016 13:16:01 +0100 From: Markus Trippelsdorf To: Borislav Petkov Cc: =?iso-8859-1?Q?M=E5ns_Rullg=E5rd?= , Thomas Voegtle , linux-kernel@vger.kernel.org Subject: Re: x86/microcode update on systems without INITRD Message-ID: <20160108121601.GC320@x4> References: <20151120071920.GA321@x4> <20151120082716.GA4028@pd.tnic> <20160107121841.GB16472@pd.tnic> <20160108105900.GA14673@pd.tnic> <20160108113641.GE14673@pd.tnic> <20160108120812.GF14673@pd.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20160108120812.GF14673@pd.tnic> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2016.01.08 at 13:08 +0100, Borislav Petkov wrote: > On Fri, Jan 08, 2016 at 11:46:28AM +0000, Måns Rullgård wrote: > > How is an initrd different from a real filesystem as seen by the > > microcode update driver? > > For starters, initrd is available much earlier, even before paging is > enabled on 32-bit, for example. See find_cpio_data(). > > > The objection against removing the dependency was that updating > > microcode "late" isn't safe. I don't see how turning on BLK_DEV_INITRD > > stops anyone doing those allegedly unsafe updates anyway. > > No one is stopping anyone from doing late updates. It is a valid use > case, and we have to support it. And late updates are not necessarily > unsafe, per se. > > Lemme put it this way: it is a lot less unproblematic to do early > updates. Mind you, there's no 100% guarantee that early updates would > always work either. It all depends on what the microcode patch does. But > they do work 99,9999999...% of the time. :) > > IOW, I haven't heard of an early update breaking the machine. But it is > possible. > > So the *general* flow should be that people enable BLK_DEV_INITRD, > put the microcode in there and it gets updated as early as possible. > This is what the distros do and it is the most tested path. The other > possibilities are there too, but only for cases where initrd is out of > the question. But you take the choice away from people like me, who don't need initrd at all. BLK_DEV_INITRD is a superfluous dependency in this case, because microcode update works perfectly well without it. -- Markus