From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758057AbYILWVM (ORCPT ); Fri, 12 Sep 2008 18:21:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756752AbYILWU5 (ORCPT ); Fri, 12 Sep 2008 18:20:57 -0400 Received: from terminus.zytor.com ([198.137.202.10]:33335 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755567AbYILWU5 (ORCPT ); Fri, 12 Sep 2008 18:20:57 -0400 Message-ID: <48CAEB40.9090303@zytor.com> Date: Fri, 12 Sep 2008 15:20:48 -0700 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.14 (X11/20080501) MIME-Version: 1.0 To: Linus Torvalds CC: David Sanders , Linux Kernel , the arch/x86 maintainers Subject: Re: nops in virtual pc x86 References: <200809121711.48558.linux@sandersweb.net> In-Reply-To: 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 Linus Torvalds wrote: > > The thing is, afaik, Virtual PC will happily let the CPU execute all the > user-space instructions, and thus they all work as well as if they were > running on real hardware - since they _do_ run on real hardware. > > But it is probably the case that Virtual PC will then do some "security > checking" of any system code, possibly by JIT'ing it or just interpreting > it, since it can't let the kernel run natively with privileges. That's > what VMware does too, since older CPU's don't have virtualization support > for ring0 programs. > > And _that_ is presumably buggy, and never learnt about the "new" > instructions in the PPro. > Actually, it's apparently worse than that. The NOPL probe instruction for dynamic testing gets executed in kernel space, and passes! Apparently at that point (and beyond) it is okay, though. Microsoft quality stuff. -hpa