Generalize memory encryption models A number of hardware platforms are implementing mechanisms whereby the hypervisor does not have unfettered access to guest memory, in order to mitigate the security impact of a compromised hypervisor. AMD's SEV implements this with in-cpu memory encryption, and Intel has its own memory encryption mechanism. POWER has an upcoming mechanism to accomplish this in a different way, using a new memory protection level plus a small trusted ultravisor. s390 also has a protected execution environment. The current code (committed or draft) for these features has each platform's version configured entirely differently. That doesn't seem ideal for users, or particularly for management layers. AMD SEV introduces a notionally generic machine option "machine-encryption", but it doesn't actually cover any cases other than SEV. This series is a proposal to at least partially unify configuration for these mechanisms, by renaming and generalizing AMD's "memory-encryption" property. It is replaced by a "confidential-guest-support" property pointing to a platform specific object which configures and manages the specific details. Note to Ram Pai: the documentation I've included for PEF is very minimal. If you could send a patch expanding on that, it would be very helpful. Changes since v8: * Rebase * Fixed some cosmetic typos Changes since v7: * Tweaked and clarified meaning of the 'ready' flag * Polished the interface to the PEF internals * Shifted initialization for s390 PV later (I hope I've finally got this after apply_cpu_model() where it needs to be) Changes since v6: * Moved to using OBJECT_DECLARE_TYPE and OBJECT_DEFINE_TYPE macros * Assorted minor fixes Changes since v5: * Renamed from "securable guest memory" to "confidential guest support" * Simpler reworking of x86 boot time flash encryption * Added a bunch of documentation * Fixed some compile errors on POWER Changes since v4: * Renamed from "host trust limitation" to "securable guest memory", which I think is marginally more descriptive * Re-organized initialization, because the previous model called at kvm_init didn't work for s390 * Assorted fixes to the s390 implementation; rudimentary testing (gitlab CI) only Changes since v3: * Rebased * Added first cut at handling of s390 protected virtualization Changes since RFCv2: * Rebased * Removed preliminary SEV cleanups (they've been merged) * Changed name to "host trust limitation" * Added migration blocker to the PEF code (based on SEV's version) Changes since RFCv1: * Rebased * Fixed some errors pointed out by Dave Gilbert