Re: [PATCH 1/1] direct mmio for passthrough - kernel part

Daniel P. Berrange
2008-04-01T18:18:56Z

On Tue, Apr 01, 2008 at 08:10:31PM +0200, Andrea Arcangeli wrote:
> On Tue, Apr 01, 2008 at 06:18:07PM +0100, Daniel P. Berrange wrote:
> > and very few application domains are allowed to access them. THe KVM/QEMU
> > policy will not allow this for example. Basically on the X server, HAL and
> > dmidecode have access in current policy. It would be undesirable to have to
> > all KVM guests full access to /dev/mem, so a more fine grained access method
> > would have benefits here.
>
> But pci-passthrough can give a root on the host even to the ring0
> guest, just like /dev/mem without VT-d, so there's no muchx difference
> with using /dev/mem as far as security is concerned. Only on the CPUs
> including VT-d it's possible to retain a mostly equivalent security
> level despite pci-passthrough.

Clearly it is a loosing battle without VT-d. That doesn't mean we should
design it to loose in general. So we should design to that when we do have
VT-D it will have the maximum security possible. VT-d will only become more
widespread over time.

Dan.
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