[PATCH v6 00/12] KVM: arm64: PSCI SYSTEM_SUSPEND support

[Oliver Upton <oupton@google.com>]

The PSCI v1.0 specification describes a call, SYSTEM_SUSPEND, which
allows software to request that the system be placed into the lowest
possible power state and await a wakeup event. This call is optional
in v1.0 and v1.1. KVM does not currently support this optional call.

This series adds support for the PSCI SYSTEM_SUSPEND call to KVM/arm64.
For reasons best described in patch 8, it is infeasible to correctly
implement PSCI SYSTEM_SUSPEND (or any system-wide event for that matter)
in a split design between kernel/userspace. As such, this series cheaply
exits to userspace so it can decide what to do with the call. This
series also gives userspace some help to emulate suspension with a new
MP state that awaits an unmasked pending interrupt.

Patches 1-5 are small reworks to more easily shoehorn the new features
into the kernel.

Patch 6 stands up the new suspend MP state, allowing userspace to
emulate the PSCI call.

Patch 7 actually allows userspace to enable the PSCI call, which
requires explicit opt-in for the new KVM_EXIT_SYSTEM_EVENT type.

Patches 8-11 clean up the way PSCI is tested in selftests to more easily
add new test cases.

Finally, the last patch actually tests that PSCI SYSTEM_SUSPEND calls
within the guest result in userspace exits.

Applies cleanly to 5.18-rc5. I'm sure you're already aware of it Marc,
but for the sake of everyone else there's some light conflict with
Raghu's patches that you've got queued up [1].

Tested with the included selftest and a hacked up kvmtool [2] with support
for the new UAPI.

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/log/?h=kvm-arm64/hcall-selection
[2]: https://lore.kernel.org/all/20220311175717.616958-1-oupton@google.com/

v5: http://lore.kernel.org/r/20220311174001.605719-1-oupton@google.com

v5 -> v6:
  - Rebase to 5.18-rc5
  - Collect Reiji's R-b's
  - Drop the system_event helper. Since we now have variadic data
    returning to userspace it doesn't make much sense to roll it up into
    a helper. Meh.
  - Put back the pointless kvm_vcpu_request() in kvm_arm_vcpu_suspend().
    We'll rip out the reliance on vCPU requests for power state later
    on. It is entirely benign, even when a vCPU targets itself.

Oliver Upton (12):
  KVM: arm64: Don't depend on fallthrough to hide SYSTEM_RESET2
  KVM: arm64: Dedupe vCPU power off helpers
  KVM: arm64: Track vCPU power state using MP state values
  KVM: arm64: Rename the KVM_REQ_SLEEP handler
  KVM: arm64: Return a value from check_vcpu_requests()
  KVM: arm64: Add support for userspace to suspend a vCPU
  KVM: arm64: Implement PSCI SYSTEM_SUSPEND
  selftests: KVM: Rename psci_cpu_on_test to psci_test
  selftests: KVM: Create helper for making SMCCC calls
  selftests: KVM: Use KVM_SET_MP_STATE to power off vCPU in psci_test
  selftests: KVM: Refactor psci_test to make it amenable to new tests
  selftests: KVM: Test SYSTEM_SUSPEND PSCI call

 Documentation/virt/kvm/api.rst                |  76 ++++++-
 arch/arm64/include/asm/kvm_host.h             |  10 +-
 arch/arm64/kvm/arm.c                          | 104 +++++++--
 arch/arm64/kvm/psci.c                         |  65 ++++--
 include/uapi/linux/kvm.h                      |   4 +
 tools/testing/selftests/kvm/.gitignore        |   2 +-
 tools/testing/selftests/kvm/Makefile          |   2 +-
 .../selftests/kvm/aarch64/psci_cpu_on_test.c  | 121 ----------
 .../testing/selftests/kvm/aarch64/psci_test.c | 213 ++++++++++++++++++
 .../selftests/kvm/include/aarch64/processor.h |  22 ++
 .../selftests/kvm/lib/aarch64/processor.c     |  25 ++
 tools/testing/selftests/kvm/steal_time.c      |  13 +-
 12 files changed, 480 insertions(+), 177 deletions(-)
 delete mode 100644 tools/testing/selftests/kvm/aarch64/psci_cpu_on_test.c
 create mode 100644 tools/testing/selftests/kvm/aarch64/psci_test.c

-- 
2.36.0.464.gb9c8b46e94-goog