On Tue, 2024-09-24 at 17:05 +0100, David Woodhouse wrote: > From: David Woodhouse <dwmw@xxxxxxxxxxxx> > > The PSCI v1.3 specification (alpha) adds support for a SYSTEM_OFF2 Can remove (alpha). > function > which is analogous to ACPI S4 state. 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). > > The beta version will be changed to say that PSCI_FEATURES returns a > bit > mask of the supported hibernate types, which is implemented here. Since the final spec has been released, we can revise or remove the above wording. > Although this new feature is inflicted unconditionally on unexpecting > userspace, it ought to be mostly OK because it still results in the > same > KVM_SYSTEM_EVENT_SHUTDOWN event, just with a new flag which hopefully > won't cause userspace to get unhappy. > > Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx> > --- > Documentation/virt/kvm/api.rst | 11 +++++++++ > arch/arm64/include/uapi/asm/kvm.h | 6 +++++ > arch/arm64/kvm/psci.c | 37 > +++++++++++++++++++++++++++++++ > 3 files changed, 54 insertions(+) > > diff --git a/Documentation/virt/kvm/api.rst > b/Documentation/virt/kvm/api.rst > index b3be87489108..2918898b7047 100644 > --- a/Documentation/virt/kvm/api.rst > +++ b/Documentation/virt/kvm/api.rst > @@ -6840,6 +6840,10 @@ the first `ndata` items (possibly zero) of the > data array are valid. > the guest issued a SYSTEM_RESET2 call according to v1.1 of the > PSCI > specification. > > + - for arm64, data[0] is set to > KVM_SYSTEM_EVENT_SHUTDOWN_FLAG_PSCI_OFF2 > + if the guest issued a SYSTEM_OFF2 call according to v1.3 of the > PSCI > + specification. > + > - for RISC-V, data[0] is set to the value of the second argument of > the > ``sbi_system_reset`` call. > > @@ -6873,6 +6877,13 @@ either: > - Deny the guest request to suspend the VM. See ARM DEN0022D.b > 5.19.2 > "Caller responsibilities" for possible return values. > > +Hibernation using the PSCI SYSTEM_OFF2 call is enabled when PSCI > v1.3 > +is enabled. If a guest invokes the PSCI SYSTEM_OFF2 function, KVM > will > +exit to userspace with the KVM_SYSTEM_EVENT_SHUTDOWN event type and > with > +data[0] set to KVM_SYSTEM_EVENT_SHUTDOWN_FLAG_PSCI_OFF2. The only > +supported hibernate type for the SYSTEM_OFF2 function is > HIBERNATE_OFF > +0x0). The spec says that the HIBERNATE_OFF parameter value is 0x1, not 0x0 (which is kind of unfortunate because it doesn't match the corresponding bit in the feature flags). So, either the BIT(PSCI_1_3_HIBERNATE_TYPE_OFF) value should be used for the SYSTEM_OFF2 functions in the code, or the definition should be changed in the header file (unless the text in the spec is wrong).
