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KVM: arm64: Add userspace flag to enable pointer authentication

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Now that the building blocks of pointer authentication are present, lets
add userspace flags KVM_ARM_VCPU_PTRAUTH_ADDRESS and
KVM_ARM_VCPU_PTRAUTH_GENERIC. These flags will enable pointer
authentication for the KVM guest on a per-vcpu basis through the ioctl
KVM_ARM_VCPU_INIT.

This features will allow the KVM guest to allow the handling of
pointer authentication instructions or to treat them as undefined
if not set.

Necessary documentations are added to reflect the changes done.

Reviewed-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Christoffer Dall <christoffer.dall@arm.com>
Cc: kvmarm@lists.cs.columbia.edu
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
This commit is contained in:
Amit Daniel Kachhap
2019-04-23 10:12:36 +05:30
committed by Marc Zyngier
parent 384b40caa8
commit a22fa321d1
5 changed files with 58 additions and 5 deletions
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22
Documentation/arm64/pointer-authentication.txt
View File

@@ -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.