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 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
