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... -- 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
