From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH] kvm: always set accessed bit in VMCS segment selectors Date: Fri, 09 Jan 2009 19:57:13 +0200 Message-ID: <49678FF9.2040404@redhat.com> References: <1231502556706-git-send-email-andre.przywara@amd.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org To: Andre Przywara Return-path: Received: from mx2.redhat.com ([66.187.237.31]:53853 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751746AbZAIR44 (ORCPT ); Fri, 9 Jan 2009 12:56:56 -0500 In-Reply-To: <1231502556706-git-send-email-andre.przywara@amd.com> Sender: kvm-owner@vger.kernel.org List-ID: Andre Przywara wrote: > Intel manual 22.3.1.2 demands that the accessed bit (bit 0 in type field) > must be set when on DS,ES,FS and GS when the selector is usable. > This fixes cross vendor migration from AMD to Intel. > > I am not sure what the real purpose of this check is, so I put this > in the VMX path and not in the SVM one. If someone has an explanation > which justifies a move, I am happy to do this. > If I understand correctly, loading a segment should set the accessed bit in the descriptor table (without virtualization there is now way to have the accessed bit clear in the segment cache), so it looks like the correct fix is to adjust svm (we already have a couple of similar fixes there). -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.