From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756863Ab3AaTed (ORCPT ); Thu, 31 Jan 2013 14:34:33 -0500 Received: from mx1.redhat.com ([209.132.183.28]:47705 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756640Ab3AaTeb (ORCPT ); Thu, 31 Jan 2013 14:34:31 -0500 Date: Thu, 31 Jan 2013 14:34:27 -0500 From: Don Zickus To: Gleb Natapov Cc: x86@kernel.org, LKML , Suresh Siddha , "H. Peter Anvin" , Prarit Bhargava Subject: Re: [PATCH] x86, x2apic: Only WARN on broken BIOSes inside a virtual guest Message-ID: <20130131193427.GP98867@redhat.com> References: <1359650435-73586-1-git-send-email-dzickus@redhat.com> <20130131185200.GA1757@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130131185200.GA1757@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 31, 2013 at 08:52:00PM +0200, Gleb Natapov wrote: > > http://www.invisiblethingslab.com/resources/2011/Software%20Attacks%20on%20Intel%20VT-d.pdf > > > > After talking with folks, the threat of irq injections on virtual guests > > made sense. However, when discussing if this was possible on bare metal > > machines, we could not come up with a plausible scenario. > > > The irq injections is something that a guest with assigned device does > to attack a hypervisor it runs on. Interrupt remapping protects host > from this attack. According to pdf above if x2apic is disabled in a > hypervisor interrupt remapping can be bypassed and leave host vulnerable > to guest attack. This means that situation is exactly opposite: warning > has sense on a bare metal, but not in a guest. I am not sure that there is > a hypervisor that emulates interrupt remapping device though and without > it the warning cannot be triggered in a guest. Ah, it makes sense. Not sure how I got it backwards then. So my patch is pointless then? I'll asked for it to be dropped. >>From my previous discussions with folks, is that KVM was protected from this type of attack. Is that still true? Cheers, Don