Merge remote-tracking branch 'remotes/dg-gitlab/tags/cgs-pull-request' into staging

Merge remote-tracking branch 'remotes/dg-gitlab/tags/cgs-pull-request' into staging

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

# gpg: Signature made Mon 08 Feb 2021 06:07:27 GMT
# gpg:                using RSA key 75F46586AE61A66CC44E87DC6C38CACA20D9B392
# gpg: Good signature from "David Gibson <david@gibson.dropbear.id.au>" [full]
# gpg:                 aka "David Gibson (Red Hat) <dgibson@redhat.com>" [full]
# gpg:                 aka "David Gibson (ozlabs.org) <dgibson@ozlabs.org>" [full]
# gpg:                 aka "David Gibson (kernel.org) <dwg@kernel.org>" [unknown]
# Primary key fingerprint: 75F4 6586 AE61 A66C C44E  87DC 6C38 CACA 20D9 B392

* remotes/dg-gitlab/tags/cgs-pull-request:
  s390: Recognize confidential-guest-support option
  confidential guest support: Alter virtio default properties for protected guests
  spapr: PEF: prevent migration
  spapr: Add PEF based confidential guest support
  confidential guest support: Update documentation
  confidential guest support: Move SEV initialization into arch specific code
  confidential guest support: Introduce cgs "ready" flag
  sev: Add Error ** to sev_kvm_init()
  confidential guest support: Rework the "memory-encryption" property
  confidential guest support: Move side effect out of machine_set_memory_encryption()
  sev: Remove false abstraction of flash encryption
  confidential guest support: Introduce new confidential guest support class
  qom: Allow optional sugar props

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>