diff options
Diffstat (limited to 'Documentation/arm64')
| -rw-r--r-- | Documentation/arm64/pointer-authentication.txt | 22 |
1 files changed, 18 insertions, 4 deletions
diff --git a/Documentation/arm64/pointer-authentication.txt b/Documentation/arm64/pointer-authentication.txt index 5baca42ba146..fc71b33de87e 100644 --- a/Documentation/arm64/pointer-authentication.txt +++ b/Documentation/arm64/pointer-authentication.txt @@ -87,7 +87,21 @@ used to get and set the keys for a thread. Virtualization -------------- -Pointer authentication is not currently supported in KVM guests. KVM -will mask the feature bits from ID_AA64ISAR1_EL1, and attempted use of -the feature will result in an UNDEFINED exception being injected into -the guest. +Pointer authentication is enabled in KVM guest when each virtual cpu is +initialised by passing flags KVM_ARM_VCPU_PTRAUTH_[ADDRESS/GENERIC] and +requesting these two separate cpu features to be enabled. The current KVM +guest implementation works by enabling both features together, so both +these userspace flags are checked before enabling pointer authentication. +The separate userspace flag will allow to have no userspace ABI changes +if support is added in the future to allow these two features to be +enabled independently of one another. + +As Arm Architecture specifies that Pointer Authentication feature is +implemented along with the VHE feature so KVM arm64 ptrauth code relies +on VHE mode to be present. + +Additionally, when these vcpu feature flags are not set then KVM will +filter out the Pointer Authentication system key registers from +KVM_GET/SET_REG_* ioctls and mask those features from cpufeature ID +register. Any attempt to use the Pointer Authentication instructions will +result in an UNDEFINED exception being injected into the guest. |