Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935209AbcCJIqq (ORCPT ); Thu, 10 Mar 2016 03:46:46 -0500 Received: from mga14.intel.com ([192.55.52.115]:14556 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932846AbcCJIqj (ORCPT ); Thu, 10 Mar 2016 03:46:39 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.24,314,1455004800"; d="scan'208";a="906804418" Subject: Re: [PATCH 1/2] KVM: MMU: fix ept=0/pte.u=0/pte.w=0/CR0.WP=0/CR4.SMEP=1/EFER.NX=0 combo To: Paolo Bonzini , linux-kernel@vger.kernel.org, kvm@vger.kernel.org References: <1457437467-65707-1-git-send-email-pbonzini@redhat.com> <1457437467-65707-2-git-send-email-pbonzini@redhat.com> Cc: stable@vger.kernel.org, Xiao Guangrong , Andy Lutomirski From: Xiao Guangrong Message-ID: <56E13454.3080604@linux.intel.com> Date: Thu, 10 Mar 2016 16:46:12 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: <1457437467-65707-2-git-send-email-pbonzini@redhat.com> 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: 552 Lines: 13 On 03/08/2016 07:44 PM, Paolo Bonzini wrote: > Yes, all of these are needed. :) This is admittedly a bit odd, but > kvm-unit-tests access.flat tests this if you run it with "-cpu host" > and of course ept=0. > > KVM handles supervisor writes of a pte.u=0/pte.w=0/CR0.WP=0 page by > setting U=0 and W=1 in the shadow PTE. This will cause a user write > to fault and a supervisor write to succeed (which is correct because > CR0.WP=0). A user read instead will flip U=0 to 1 and W=1 back to 0. BTW, it should be pte.u = 1 where you mentioned above.