| Marc Zyngier | 85bd0ba | 2018-01-21 16:42:56 +0000 | [diff] [blame] | 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. |
| 4 | |
| 5 | The PSCI specification is regularly updated to provide new features, |
| 6 | and KVM implements these updates if they make sense from a virtualization |
| 7 | point of view. |
| 8 | |
| 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. |
| 14 | |
| 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. |
| 19 | |
| 20 | The following register is defined: |
| 21 | |
| 22 | * KVM_REG_ARM_PSCI_VERSION: |
| 23 | |
| 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) |