From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932164AbWGRKPr (ORCPT ); Tue, 18 Jul 2006 06:15:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932163AbWGRKPq (ORCPT ); Tue, 18 Jul 2006 06:15:46 -0400 Received: from [216.208.38.107] ([216.208.38.107]:50304 "EHLO OTTLS.pngxnet.com") by vger.kernel.org with ESMTP id S932160AbWGRKPq (ORCPT ); Tue, 18 Jul 2006 06:15:46 -0400 Subject: Re: [RFC PATCH 18/33] Subarch support for CPUID instruction From: Arjan van de Ven To: Chris Wright Cc: linux-kernel@vger.kernel.org, virtualization@lists.osdl.org, xen-devel@lists.xensource.com, Jeremy Fitzhardinge , Andi Kleen , Andrew Morton , Rusty Russell , Zachary Amsden , Ian Pratt , Christian Limpach In-Reply-To: <20060718091953.003336000@sous-sol.org> References: <20060718091807.467468000@sous-sol.org> <20060718091953.003336000@sous-sol.org> Content-Type: text/plain Organization: Intel International BV Date: Tue, 18 Jul 2006 12:14:46 +0200 Message-Id: <1153217686.3038.37.camel@laptopd505.fenrus.org> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 (2.2.3-2.fc4) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2006-07-18 at 00:00 -0700, Chris Wright wrote: > plain text document attachment (i386-cpuid) > Allow subarchitectures to modify the CPUID instruction. This allows > the subarch to provide a limited set of CPUID feature flags during CPU > identification. Add a subarch implementation for Xen that traps to the > hypervisor where unsupported feature flags can be hidden from guests. Hi, I'm wondering if this is entirely the wrong level of abstraction; to me it feels the subarch shouldn't override the actual cpuid, but the cpu feature flags that linux uses. That's a lot less messy: cpuid has many many pieces of information which are near impossible to filter in practice, however filtering the USAGE of it is trivial; linux basically flattens the cpuid namespace into a simple bitmap of "what the kernel can use". That is really what the subarch should filter/fixup, just like we do for cpu quirks etc etc. Greetings, Arjan van de Ven