[RFC PATCH v3 0/5] Add PSCI v1.3 SYSTEM_OFF2 support for hibernation

[David Woodhouse]

The PSCI v1.3 spec (https://developer.arm.com/documentation/den0022,
currently in Alpha state, hence 'RFC') adds support for a SYSTEM_OFF2
function enabling a HIBERNATE_OFF state which is analogous to ACPI S4.
This will allow hosting environments to determine that a guest is
hibernated rather than just powered off, and ensure that they preserve
the virtual environment appropriately to allow the guest to resume
safely (or bump the hardware_signature in the FACS to trigger a clean
reboot instead).

This updates KVM to support advertising PSCI v1.3, and unconditionally
enables the SYSTEM_OFF2 support when PSCI v1.3 is enabled. For now,
KVM defaults to PSCI v1.2 unless explicitly requested.

For the guest side, add a new SYS_OFF_MODE_POWER_OFF handler with higher
priority than the EFI one, but which *only* triggers when there's a
hibernation in progress. There are other ways to do this (see the commit
message for more details) but this seemed like the simplest.

Version 2 of the patch series splits out the psci.h definitions into a
separate commit (a dependency for both the guest and KVM side), and adds
definitions for the other new functions added in v1.3. It also moves the
pKVM psci-relay support to a separate commit; although in arch/arm64/kvm
that's actually about the *guest* side of SYSTEM_OFF2 (i.e. using it
from the host kernel, relayed through nVHE).

Version 3 dropped the KVM_CAP which allowed userspace to explicitly opt
in to the new feature like with SYSTEM_SUSPEND, and makes it depend only
on PSCI v1.3 being exposed to the guest.

David Woodhouse (5):
      firmware/psci: Add definitions for PSCI v1.3 specification (ALPHA)
      KVM: arm64: Add support for PSCI v1.2 and v1.3
      KVM: arm64: Add PSCI v1.3 SYSTEM_OFF2 function for hibernation
      KVM: arm64: nvhe: Pass through PSCI v1.3 SYSTEM_OFF2 call
      arm64: Use SYSTEM_OFF2 PSCI call to power off for hibernate

 Documentation/virt/kvm/api.rst       | 11 +++++++++
 arch/arm64/include/uapi/asm/kvm.h    |  6 +++++
 arch/arm64/kvm/hyp/nvhe/psci-relay.c |  2 ++
 arch/arm64/kvm/hypercalls.c          |  2 ++
 arch/arm64/kvm/psci.c                | 43 +++++++++++++++++++++++++++++++++++-
 drivers/firmware/psci/psci.c         | 35 +++++++++++++++++++++++++++++
 include/kvm/arm_psci.h               |  4 +++-
 include/uapi/linux/psci.h            | 20 +++++++++++++++++
 kernel/power/hibernate.c             |  5 ++++-
 9 files changed, 125 insertions(+), 3 deletions(-)