[RFC PATCH v4 24/26] KVM: arm64: Trap disabled features of ID_AA64ISAR1_EL1

[Reiji Watanabe <reijiw@google.com>]

Add feature_config_ctrl for PTRAUTH, which is indicated in
ID_AA64ISAR1_EL1, to program configuration register to trap
guest's using the feature when it is not exposed to the guest.

Signed-off-by: Reiji Watanabe <reijiw@google.com>
---
 arch/arm64/kvm/sys_regs.c | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index f8a5ee927ecf..e6ef76f9b563 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -283,6 +283,30 @@ static bool trap_raz_wi(struct kvm_vcpu *vcpu,
 	(cpuid_feature_extract_unsigned_field(val, ID_AA64ISAR1_GPI_SHIFT) >= \
 	 ID_AA64ISAR1_GPI_IMP_DEF)
 
+/*
+ * Return true if ptrauth needs to be trapped.
+ * (i.e. if ptrauth is supported on the host but not exposed to the guest)
+ */
+static bool vcpu_need_trap_ptrauth(struct kvm_vcpu *vcpu)
+{
+	u64 val;
+	bool generic, address;
+
+	if (!system_has_full_ptr_auth())
+		/* The feature is not supported. */
+		return false;
+
+	val = __read_id_reg(vcpu, SYS_ID_AA64ISAR1_EL1);
+	generic = aa64isar1_has_gpi(val) || aa64isar1_has_gpa(val);
+	address = aa64isar1_has_api(val) || aa64isar1_has_apa(val);
+	if (generic && address)
+		/* The feature is available. */
+		return false;
+
+	/* The feature is supported but hidden. */
+	return true;
+}
+
 /*
  * Feature information to program configuration register to trap or disable
  * guest's using a feature when the feature is not exposed to the guest.
@@ -370,6 +394,11 @@ static void feature_lor_trap_activate(struct kvm_vcpu *vcpu)
 	feature_trap_activate(vcpu, VCPU_HCR_EL2, HCR_TLOR, 0);
 }
 
+static void feature_ptrauth_trap_activate(struct kvm_vcpu *vcpu)
+{
+	feature_trap_activate(vcpu, VCPU_HCR_EL2, 0, HCR_API | HCR_APK);
+}
+
 /* For ID_AA64PFR0_EL1 */
 static struct feature_config_ctrl ftr_ctrl_ras = {
 	.ftr_reg = SYS_ID_AA64PFR0_EL1,
@@ -430,6 +459,12 @@ static struct feature_config_ctrl ftr_ctrl_lor = {
 	.trap_activate = feature_lor_trap_activate,
 };
 
+/* For SYS_ID_AA64ISAR1_EL1 */
+static struct feature_config_ctrl ftr_ctrl_ptrauth = {
+	.ftr_need_trap = vcpu_need_trap_ptrauth,
+	.trap_activate = feature_ptrauth_trap_activate,
+};
+
 struct id_reg_info {
 	u32	sys_reg;	/* Register ID */
 	u64	sys_val;	/* Sanitized system value */
@@ -932,6 +967,10 @@ static struct id_reg_info id_aa64isar1_el1_info = {
 	.init = init_id_aa64isar1_el1_info,
 	.validate = validate_id_aa64isar1_el1,
 	.vcpu_mask = vcpu_mask_id_aa64isar1_el1,
+	.trap_features = &(const struct feature_config_ctrl *[]) {
+		&ftr_ctrl_ptrauth,
+		NULL,
+	},
 };
 
 static struct id_reg_info id_aa64mmfr0_el1_info = {
-- 
2.34.1.448.ga2b2bfdf31-goog