From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754602Ab2FJRio (ORCPT ); Sun, 10 Jun 2012 13:38:44 -0400 Received: from mx1.redhat.com ([209.132.183.28]:3406 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752836Ab2FJRin (ORCPT ); Sun, 10 Jun 2012 13:38:43 -0400 Message-ID: <1339349905.26976.306.camel@ul30vt> Subject: Re: [PATCH] uio_pci_generic does not export memory resources From: Alex Williamson To: "Michael S. Tsirkin" Cc: "Hans J. Koch" , Andreas Hartmann , Dominic Eschweiler , Jan Kiszka , Greg Kroah-Hartman , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Date: Sun, 10 Jun 2012 11:38:25 -0600 In-Reply-To: <20120610164429.GB9879@redhat.com> References: <1339156616.3870.9.camel@blech> <20120608130351.GB1964@redhat.com> <4FD1FB49.3020905@siemens.com> <1339165009.26976.60.camel@ul30vt> <1339166867.3870.29.camel@blech> <4FD22552.6090609@01019freenet.de> <20120608164426.GE9705@local> <1339175476.26976.102.camel@ul30vt> <20120610141759.GB8922@redhat.com> <1339344566.26976.272.camel@ul30vt> <20120610164429.GB9879@redhat.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 2012-06-10 at 19:44 +0300, Michael S. Tsirkin wrote: > On Sun, Jun 10, 2012 at 10:09:26AM -0600, Alex Williamson wrote: > > On Sun, 2012-06-10 at 17:18 +0300, Michael S. Tsirkin wrote: > > > On Fri, Jun 08, 2012 at 11:11:16AM -0600, Alex Williamson wrote: > > > > On Fri, 2012-06-08 at 18:44 +0200, Hans J. Koch wrote: > > > > > On Fri, Jun 08, 2012 at 06:16:18PM +0200, Andreas Hartmann wrote: > > > > > > Hi Dominic, > > > > > > > > > > > > Dominic Eschweiler wrote: > > > > > > > Am Freitag, den 08.06.2012, 08:16 -0600 schrieb Alex Williamson: > > > > > > >> Yes, thanks Jan. This is exactly what VFIO does. VFIO provides > > > > > > >> secure config space access, resource access, DMA mapping services, and > > > > > > >> full interrupt support to userspace. > > > > > > > > > > VFIO is not a "better UIO". It *requires* an IOMMU. Dominic didn't say on > > > > > what CPU he's working, so it's not clear if he can use VFIO at all. > > > > > > > > > > UIO is intended for general use with devices that have mappable registers > > > > > and don't fit into any other subsystem. No more, no less. > > > > > > > > VFIO is a secure UIO. > > > > > > A secure UIO *for VFs*. I think that's why it's called VFIO :). > > > Other stuff sometimes also works but no real guarantees, though > > > VFIO tries to make sure you don't burn yourself too badly > > > if it breaks. > > > > We do a little better than that. Multifunction devices that don't > > explicitly report ACS support are grouped together, so we have security > > for multifunction devices as well. > > How can you get security with insecure hardware? > > So you prevent the device from writing to host memory? Cool. > Now guest puts a virus on an on-card flash, the > moment device is assigned to another VM it will own that, > or host if it's enabled in host. > > I can make up more silliness. Buggy userspace can brick the device, > e.g. by damaging the internal eeprom memory, and these things were known > to happen even by accident. > > Simply put if you want secure userspace drivers you must be able to > trust your hardware for security and the only hardware that promises you > security is a VF in an SRIOV device. Next I suppose you're going to say assigning a NIC to a guest is insecure because it could host a malicious OS that infects other systems on the network. So to clarify, by secure, I mean that users of VFIO devices don't have access to the host. The host still needs to be suspicious of any data the user might have tainted after a device is returned. > > Either single of multifunction PFs > > can have an option ROM, but since there's no defined mechanism to > > program the ROM, we can't protect it. Secure boot actually helps us > > here since the ROM loaded by the host BIOS or drivers would need to > > verify the ROM before using it. Note that secure boot will likely close > > off the pci-sysfs path uio_pci and KVM device assignment use to get > > resources since it allows unprotected access to the system. VFIO > > provides an interface where we control secure access, so should be > > compatible with secure boot. Thanks, > > > > Alex > > IMHO all this means VFIO *works* not just for VFs. > Not that it's secure. By your argument above, not even VFs are "secure". A user could just as easily taint a disk attached to an HBA VF...