1 KVM implements the PSCI (Power State Coordination Interface)
2 specification in order to provide services such as CPU on/off, reset
3 and power-off to the guest.
5 The PSCI specification is regularly updated to provide new features,
6 and KVM implements these updates if they make sense from a virtualization
9 This means that a guest booted on two different versions of KVM can
10 observe two different "firmware" revisions. This could cause issues if
11 a given guest is tied to a particular PSCI revision (unlikely), or if
12 a migration causes a different PSCI version to be exposed out of the
13 blue to an unsuspecting guest.
15 In order to remedy this situation, KVM exposes a set of "firmware
16 pseudo-registers" that can be manipulated using the GET/SET_ONE_REG
17 interface. These registers can be saved/restored by userspace, and set
18 to a convenient value if required.
20 The following register is defined:
22 * KVM_REG_ARM_PSCI_VERSION:
24 - Only valid if the vcpu has the KVM_ARM_VCPU_PSCI_0_2 feature set
25 (and thus has already been initialized)
26 - Returns the current PSCI version on GET_ONE_REG (defaulting to the
27 highest PSCI version implemented by KVM and compatible with v0.2)
28 - Allows any PSCI version implemented by KVM and compatible with
29 v0.2 to be set with SET_ONE_REG
30 - Affects the whole VM (even if the register view is per-vcpu)