On 6/19/23 05:21, David Hildenbrand wrote: > So, ordinary writes to TD private memory are not a problem? I thought > one motivation for the unmapped-guest-memory discussion was to prevent > host (userspace) writes to such memory because it would trigger a MC and > eventually crash the host. Those are two different problems. Problem #1 (this patch): The host encounters poison when going about its normal business accessing normal memory. This happens when something in the host accidentally clobbers some TDX memory and *then* reads it. Only occurs with partial writes. Problem #2 (addressed with unmapping): Host *userspace* intentionally and maliciously clobbers some TDX memory and then the TDX module or a TDX guest can't run because the memory integrity checks (checksum or TD bit) fail. This can also take the system down because #MC's are nasty. Host userspace unmapping doesn't prevent problem #1 because it's the kernel who screwed up with the _kernel_ mapping.
