From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH] uio_pci_generic does not export memory resources Date: Sun, 10 Jun 2012 22:00:36 +0300 Message-ID: <20120610190036.GD10523@redhat.com> References: <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> <1339349905.26976.306.camel@ul30vt> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "Hans J. Koch" , Andreas Hartmann , Dominic Eschweiler , Jan Kiszka , Greg Kroah-Hartman , kvm@vger.kernel.org, linux-kernel@vger.kernel.org To: Alex Williamson Return-path: Content-Disposition: inline In-Reply-To: <1339349905.26976.306.camel@ul30vt> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Sun, Jun 10, 2012 at 11:38:25AM -0600, Alex Williamson wrote: > 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. One thing I stand corrected on: assigning a PF that does DMA with VFIO *might* be secure, and sometimes, maybe often, is. There's just no way to make sure. This is unlike uio_pci_generic where it would always be insecure. -- MST