[PATCH v5 0/5] Add PSCI v1.3 SYSTEM_OFF2 support for hibernation

David Woodhouse
2024-09-26T18:46:05Z

The PSCI v1.3 spec (https://developer.arm.com/documentation/den0022)
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 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.

Version 4 is no longer RFC, as the PSCI v1.3 spec is finally published.
Minor fixes from the last round of review, and an added KVM self test.

Version 5 drops some of the changes which didn't make it to the final
v1.3 spec, and cleans up a couple of places which still referred to it
as 'alpha' or 'beta'. It also temporarily drops the guest-side patch to
invoke SYSTEM_OFF2 for hibernation, pending confirmation that the final
PSCI v1.3 spec just has a typo where it changed to saying that 0x1
should be passed to mean HIBERNATE_OFF, even though it's advertised as
bit 0. That can be sent under separate cover, and perhaps should have
been anyway. The change in question doesn't matter for any of the KVM
patches, because we just treat SYSTEM_OFF2 like the existing
SYSTEM_RESET2, setting a flag to indicate that it was a SYSTEM_OFF2
call, but not actually caring about the argument; that's for userspace
to worry about.

David Woodhouse (5):
firmware/psci: Add definitions for PSCI v1.3 specification
KVM: arm64: Add PSCI v1.3 SYSTEM_OFF2 function for hibernation
KVM: arm64: Add support for PSCI v1.2 and v1.3
KVM: selftests: Add test for PSCI SYSTEM_OFF2
KVM: arm64: nvhe: Pass through PSCI v1.3 SYSTEM_OFF2 call

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 ++++++++++++++++-
include/kvm/arm_psci.h | 4 +-
include/uapi/linux/psci.h | 5 ++
tools/testing/selftests/kvm/aarch64/psci_test.c | 61 +++++++++++++++++++++++++
8 files changed, 132 insertions(+), 2 deletions(-)