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. > > 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. *Of course* it is less secure than a firewalled guest with a virtual NIC. You argue this is not true? But at least there are ways to contain a NIC on a network. So it depends on the setup. Not so for an assigned PF. It depends on the internals of the PF which you have no idea about. > So to clarify, by secure, I mean that users of VFIO > devices don't have access to the host. Yes. And since you can't guarantee it for PFs, it's insecure. > The host still needs to be > suspicious of any data the user might have tainted That's not the only point. Host data might also leak to guest when device is assigned. > after a device is returned. For a VF you have a way to validate what the VF does. For a PF there is no way to be suspicious of the device state. > > > 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". VFs can be secure if PF hardware and driver are secure. There's no sure way to secure a PF. > A user could just as > easily taint a disk attached to an HBA VF... But if I don't run stuff from this disk I am safe. What is the way to guarantee security with an assigned PF? -- 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
