Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757706AbZCPAFn (ORCPT ); Sun, 15 Mar 2009 20:05:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752287AbZCPAFd (ORCPT ); Sun, 15 Mar 2009 20:05:33 -0400 Received: from gw.goop.org ([64.81.55.164]:39495 "EHLO mail.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751122AbZCPAFc (ORCPT ); Sun, 15 Mar 2009 20:05:32 -0400 Message-ID: <49BD97C6.2070401@goop.org> Date: Sun, 15 Mar 2009 17:05:26 -0700 From: Jeremy Fitzhardinge User-Agent: Thunderbird 2.0.0.19 (X11/20090105) MIME-Version: 1.0 To: Arjan van de Ven CC: "H. Peter Anvin" , Jan Beulich , Xen-devel , Jeremy Fitzhardinge , the arch/x86 maintainers , Linux Kernel Mailing List Subject: Re: [Xen-devel] [PATCH 10/24] xen: mask XSAVE from cpuid References: <1236931920-6861-1-git-send-email-jeremy@goop.org> <1236931920-6861-11-git-send-email-jeremy@goop.org> <49BA3A84.76E4.0078.0@novell.com> <49BA7810.6090807@goop.org> <49BD4CE1.6040100@zytor.com> <49BD6D0E.1010107@goop.org> <20090315154718.00353625@infradead.org> In-Reply-To: <20090315154718.00353625@infradead.org> X-Enigmail-Version: 0.95.6 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1018 Lines: 22 Arjan van de Ven wrote: > This is indicative of something that might be a huge bug in Xen: > Xen should never ever pass through CPUID bits it does not know. > If Xen does not honor that, there is a fundamental and eternally > recurring problem.... every time something new gets introduced Xen > likely breaks. Yes, I'd agree; Xen should whitelist cpu capabilities rather than blacklist them. Jan expressed the opposite opinion (on the grounds that it precludes using features which don't require special OS or hypervisor support without Xen modifications). But if its just a matter of sticking a bit into a mask, its easy and quick to roll a new version of Xen (esp since it can generally be done before CPUs with the new feature get into people's hands). J -- 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/