From: Edgecombe, Rick P <rick.p.edgecombe@xxxxxxxxx> Sent: Friday, March 1, 2024 11:13 AM > > > > > On TDX it is possible for the untrusted host to cause > > > > I'd argue that this is for CoCo VMs in general, not just TDX. I don't know > > all the failure modes for SEV-SNP, but the code paths you are changing > > are run in both TDX and SEV-SNP CoCo VMs. > > On SEV-SNP the host can cause the call to fail too was my > understanding. But in Linux, that side panics and never gets to the > point of being able to free the shared memory. So it's not TDX > architecture specific, it's just how Linux handles it on the different > sids. For TDX the suggestion was to avoid panicing because it is > possible to handle in SW, as Linux usually tries it's best to do. > The Hyper-V case can actually be a third path when a paravisor is being used. In that case, for both TDX and SEV-SNP, the hypervisor callbacks in __set_memory_enc_pgtable() go to Hyper-V specific functions that talk to the paravisor. Those callbacks never panic. After a failure, either at the paravisor level or in the paravisor talking to the hypervisor/VMM, the decrypted/encrypted state of the memory isn't known. So leaking the memory is still the right thing to do, and your patch set is good. But in the Hyper-V with paravisor case, the leaking is applicable more broadly than just TDX. The text in the commit message isn't something that I'll go to the mat over. But I wanted to offer the slightly broader perspective. Michael
