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

From: David Woodhouse <dwmw2@infradead.org>
To: linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>,
	Jonathan Corbet <corbet@lwn.net>, Marc Zyngier <maz@kernel.org>,
	Oliver Upton <oliver.upton@linux.dev>,
	James Morse <james.morse@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Zenghui Yu <yuzenghui@huawei.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Lorenzo Pieralisi <lpieralisi@kernel.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>,
	David Woodhouse <dwmw@amazon.co.uk>,
	Mostafa Saleh <smostafa@google.com>,
	Jean-Philippe Brucker <jean-philippe@linaro.org>,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	kvmarm@lists.linux.dev, linux-pm@vger.kernel.org
Subject: [RFC PATCH v3 0/5] Add PSCI v1.3 SYSTEM_OFF2 support for hibernation
Date: Tue, 19 Mar 2024 12:59:01 +0000	[thread overview]
Message-ID: <20240319130957.1050637-1-dwmw2@infradead.org> (raw)

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(-)