Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754117Ab2FLU6s (ORCPT ); Tue, 12 Jun 2012 16:58:48 -0400 Received: from terminus.zytor.com ([198.137.202.10]:45790 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753176Ab2FLU6r (ORCPT ); Tue, 12 Jun 2012 16:58:47 -0400 Message-ID: <4FD7AD6F.6010008@zytor.com> Date: Tue, 12 Jun 2012 13:58:23 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20120430 Thunderbird/12.0.1 MIME-Version: 1.0 To: Borislav Petkov CC: Peter Zijlstra , Stephane Eranian , linux-kernel@vger.kernel.org, andi@firstfloor.org, mingo@elte.hu, ming.m.lin@intel.com, "Yu, Fenghua" Subject: Re: [PATCH] perf/x86: check ucode before disabling PEBS on SandyBridge References: <20120607071531.GA4849@quad> <4FD78BE6.4060207@zytor.com> <20120612190720.GA11137@aftab.osrc.amd.com> <1339529614.31548.104.camel@twins> <20120612194900.GC11137@aftab.osrc.amd.com> <4FD7A687.3040500@zytor.com> <20120612203730.GE11137@aftab.osrc.amd.com> <4FD7A99F.8030007@zytor.com> <20120612205609.GF11137@aftab.osrc.amd.com> In-Reply-To: <20120612205609.GF11137@aftab.osrc.amd.com> X-Enigmail-Version: 1.4.2 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1174 Lines: 33 On 06/12/2012 01:56 PM, Borislav Petkov wrote: > On Tue, Jun 12, 2012 at 01:42:07PM -0700, H. Peter Anvin wrote: >> I personally don't know of any valid use case for per-core loads, and >> it sounds like a horrid idea. > > Vehemently agreed. > > However, last time we talked about Ingo mentioned some possibility > of having different microcode versions on different CPUs: > http://lkml.indiana.edu/hypermail/linux/kernel/1105.3/00749.html > > Hmm... > >> And yes, I would prefer a single sysfs file, or better yet a plain old >> device node. > > Also agreed. > There is a difference here. Mixed steppings or even mixed CPUs are, indeed, supported (even things like Nehalem + Westmere in the same system). However, the notion is that we should upload the *entire set* of microcodes to the kernel, and let it flash the appropriate one into each CPU. This may result in different version number on different CPUs. -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/