From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" Subject: Re: KVM crash on unusual PM->RM transition Date: Mon, 13 Apr 2009 22:42:56 -0700 Message-ID: <49E42260.7030009@zytor.com> References: <49E3CDE1.8010001@zytor.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit To: kvm@vger.kernel.org Return-path: Received: from terminus.zytor.com ([198.137.202.10]:46124 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751711AbZDNFm6 (ORCPT ); Tue, 14 Apr 2009 01:42:58 -0400 In-Reply-To: <49E3CDE1.8010001@zytor.com> Sender: kvm-owner@vger.kernel.org List-ID: H. Peter Anvin wrote: > The current test branch of Syslinux does PM->RM transition via a stub > which can be located in high memory. This is correct and valid (x86 > CPUs rely on this to boot): after clearing CR0.PE, CS.base retains its > previous value until CS is reloaded by a far JMP (which in this case is > the very next instruction). Some trivial research later... It looks like KVM will simply crash when it runs into a real-mode state it can't approximate with V86 mode. I guess I had the failed notion that it would kick back such "impossible" states to Qemu. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.