On Thu, 2024-04-25 at 15:53 -0700, Sean Christopherson wrote: > > Hmm. I'll mention this, but I don't see why KVM needs the TDX module to > > filter > > it. It seems in the range of userspace being allowed to create nonsense > > configurations that only hurt its own guest. > > Because the whole point of TDX is to protect the guest from the bad, naughty > host? DOS naughtiness by the host is allowed though. > > > If we think the TDX module should do it, then maybe we should have KVM > > sanity > > filter these out today in preparation. > > Nope. KVM isn't in the guest's TCB, TDX is. > KVM's stance is that userspace is > responsible for providing a sane vCPU model, because defining what is "sane" > is > extremely difficult unless the definition is super prescriptive, a la TDX. > > E.g. letting the host map something that TDX's spec says will cause #VE would > create a novel attack surface. I thought that the shared half could be mapped in that range unless KVM gets involved. But, no, as long as we tie GPAW, 23:16, ept-level all together, then mapping something above it won't even make sense. I don't see attack surface risk immediately. I expect this will get more internal scrutiny in that regard though.
