From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: KVM Page Fault Question Date: Fri, 19 Mar 2010 10:39:15 +0200 Message-ID: <4BA33833.8060703@redhat.com> References: <4B9726A7.7000800@csail.mit.edu> <4B976AA8.9030904@redhat.com> <4B9833EE.1070705@csail.mit.edu> <4B989035.4050109@redhat.com> <4B9916DE.30209@csail.mit.edu> <4B9B5225.2050604@redhat.com> <4BA2BC2A.8090803@csail.mit.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org To: Marek Olszewski Return-path: Received: from mx1.redhat.com ([209.132.183.28]:63859 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753091Ab0CSIjU (ORCPT ); Fri, 19 Mar 2010 04:39:20 -0400 In-Reply-To: <4BA2BC2A.8090803@csail.mit.edu> Sender: kvm-owner@vger.kernel.org List-ID: On 03/19/2010 01:50 AM, Marek Olszewski wrote: > When using VMX without EPT, is it ever possible for a guest to receive > a page fault without it first appearing (and being reinjected) in KVM? Yes. On Intel hosts only, and controlled by bypass_guest_pf. > I'm seeing some strange behavior where accesses to mprotected (but yet > to be accessed) memory causes a fault in the guest OS, that I cannot > see KVM intercepting. > Look for 'shadow_trap_nonpresent_pte' (which will trap into kvm) and 'shadow_notrap_nonpresent_pte' (which will not) in the code. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic.