[PATCH 4/8] KVM: arm64: Hoist PAuth checks into KVM_ARM_VCPU_INIT ioctl

Oliver Upton
2023-09-20T19:50:58Z

Test for feature support in the ioctl handler rather than
kvm_reset_vcpu(). Continue to uphold our all-or-nothing policy with
address and generic pointer authentication.

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
---
arch/arm64/kvm/arm.c | 13 +++++++++++++
arch/arm64/kvm/reset.c | 21 +++------------------
2 files changed, 16 insertions(+), 18 deletions(-)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 9415a760fcda..e40f3bfcb0a1 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1203,6 +1203,11 @@ static unsigned long system_supported_vcpu_features(void)
if (!system_supports_sve())
clear_bit(KVM_ARM_VCPU_SVE, &features);

+ if (!system_has_full_ptr_auth()) {
+ clear_bit(KVM_ARM_VCPU_PTRAUTH_ADDRESS, &features);
+ clear_bit(KVM_ARM_VCPU_PTRAUTH_GENERIC, &features);
+ }
+
return features;
}

@@ -1223,6 +1228,14 @@ static int kvm_vcpu_init_check_features(struct kvm_vcpu *vcpu,
if (features & ~system_supported_vcpu_features())
return -EINVAL;

+ /*
+ * For now make sure that both address/generic pointer authentication
+ * features are requested by the userspace together.
+ */
+ if (test_bit(KVM_ARM_VCPU_PTRAUTH_ADDRESS, &features) !=
+ test_bit(KVM_ARM_VCPU_PTRAUTH_GENERIC, &features))
+ return -EINVAL;
+
if (!test_bit(KVM_ARM_VCPU_EL1_32BIT, &features))
return 0;

diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index 3cb08d35b8e0..bbcf5bbd66d9 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -165,20 +165,9 @@ static void kvm_vcpu_reset_sve(struct kvm_vcpu *vcpu)
memset(vcpu->arch.sve_state, 0, vcpu_sve_state_size(vcpu));
}

-static int kvm_vcpu_enable_ptrauth(struct kvm_vcpu *vcpu)
+static void kvm_vcpu_enable_ptrauth(struct kvm_vcpu *vcpu)
{
- /*
- * For now make sure that both address/generic pointer authentication
- * features are requested by the userspace together and the system
- * supports these capabilities.
- */
- if (!test_bit(KVM_ARM_VCPU_PTRAUTH_ADDRESS, vcpu->arch.features) ||
- !test_bit(KVM_ARM_VCPU_PTRAUTH_GENERIC, vcpu->arch.features) ||
- !system_has_full_ptr_auth())
- return -EINVAL;
-
vcpu_set_flag(vcpu, GUEST_HAS_PTRAUTH);
- return 0;
}

/**
@@ -233,12 +222,8 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
}

if (test_bit(KVM_ARM_VCPU_PTRAUTH_ADDRESS, vcpu->arch.features) ||
- test_bit(KVM_ARM_VCPU_PTRAUTH_GENERIC, vcpu->arch.features)) {
- if (kvm_vcpu_enable_ptrauth(vcpu)) {
- ret = -EINVAL;
- goto out;
- }
- }
+ test_bit(KVM_ARM_VCPU_PTRAUTH_GENERIC, vcpu->arch.features))
+ kvm_vcpu_enable_ptrauth(vcpu);

if (vcpu_el1_is_32bit(vcpu))
pstate = VCPU_RESET_PSTATE_SVC;
--
2.42.0.515.g380fc7ccd1-goog