[PATCH v2 13/13] KVM: arm64: Check vcpu features at pVM creation

[Fuad Tabba <tabba@google.com>]

Check that a protected VM enabled only supported features when
created.

Signed-off-by: Fuad Tabba <tabba@google.com>
---
 arch/arm64/kvm/pkvm.c | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/arch/arm64/kvm/pkvm.c b/arch/arm64/kvm/pkvm.c
index cf624350fb27..15a92f3fdd44 100644
--- a/arch/arm64/kvm/pkvm.c
+++ b/arch/arm64/kvm/pkvm.c
@@ -88,10 +88,53 @@ static void pkvm_teardown_firmware_slot(struct kvm *kvm)
 	kvm->arch.pkvm.firmware_slot = NULL;
 }
 
+/*
+ * Check that only supported features are enabled for the protected VM's vcpus.
+ *
+ * Return 0 if all features enabled for all vcpus are supported, or -EINVAL if
+ * one or more vcpus has one or more unsupported features.
+ */
+static int pkvm_check_features(struct kvm *kvm)
+{
+	int i;
+	const struct kvm_vcpu *vcpu;
+	DECLARE_BITMAP(allowed_features, KVM_VCPU_MAX_FEATURES);
+
+	bitmap_zero(allowed_features, KVM_VCPU_MAX_FEATURES);
+
+	/*
+	 * Support for:
+	 * - CPU starting in poweroff state
+	 * - PSCI v0.2
+	 * - Pointer authentication: address or generic
+	 *
+	 * No support for remaining features, i.e.,:
+	 * - AArch32 state
+	 * - Performance Monitoring
+	 * - Scalable Vectors
+	 */
+	set_bit(KVM_ARM_VCPU_POWER_OFF, allowed_features);
+	set_bit(KVM_ARM_VCPU_PSCI_0_2, allowed_features);
+	set_bit(KVM_ARM_VCPU_PTRAUTH_ADDRESS, allowed_features);
+	set_bit(KVM_ARM_VCPU_PTRAUTH_GENERIC, allowed_features);
+
+	kvm_for_each_vcpu(i, vcpu, kvm) {
+		if (!bitmap_subset(vcpu->arch.features, allowed_features,
+				   KVM_VCPU_MAX_FEATURES))
+			return -EINVAL;
+	}
+
+	return 0;
+}
+
 static int pkvm_enable(struct kvm *kvm, u64 slotid)
 {
 	int ret;
 
+	ret = pkvm_check_features(kvm);
+	if (ret)
+		return ret;
+
 	ret = pkvm_init_firmware_slot(kvm, slotid);
 	if (ret)
 		return ret;
-- 
2.32.0.272.g935e593368-goog