[PATCH v3 6/7] arm64: docs: document KVM support of pointer authentication

From: Amit Daniel Kachhap
Date: Wed Oct 17 2018 - 06:49:21 EST

The documentation is updated to help in using pointer authentication
for KVM guests.

Signed-off-by: Amit Daniel Kachhap <amit.kachhap@xxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Christoffer Dall <christoffer.dall@xxxxxxx>
Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
Cc: kvmarm@xxxxxxxxxxxxxxxxxxxxx
Documentation/arm64/pointer-authentication.txt | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/Documentation/arm64/pointer-authentication.txt b/Documentation/arm64/pointer-authentication.txt
index 8a9cb57..b00d735 100644
--- a/Documentation/arm64/pointer-authentication.txt
+++ b/Documentation/arm64/pointer-authentication.txt
@@ -78,7 +78,13 @@ to TTBR1 addresses (e.g. kernel pointers).

-Pointer authentication is not currently supported in KVM guests. KVM
+Pointer authentication is enabled in KVM guest when virtual machine is
+created by passing a flag requesting this feature to be enabled. Without
+this flag, pointer authentication is not enabled in KVM guests and 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.
+The flag to enable this feature is KVM_ARM_VCPU_PTRAUTH and should be
+used in KVM API KVM_ARM_VCPU_INIT. The pointer authentication key
+registers are hidden from userspace if this feature is not enabled.