KVM: arm64: Log an error if trapping a read-from-write-only GICv3 access

A read-from-write-only GICv3 access should UNDEF at EL1. But since
we're in complete paranoia-land with broken CPUs, let's assume the
worse and gracefully handle the case.
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Reviewed-by: Christoffer Dall <cdall@linaro.org>
Signed-off-by: Christoffer Dall <cdall@linaro.org>

arch/arm64/kvm/sys_regs.c

@@ -56,7 +56,8 @@
  */
 
 static bool read_from_write_only(struct kvm_vcpu *vcpu,
-				 const struct sys_reg_params *params)
+				 struct sys_reg_params *params,
+				 const struct sys_reg_desc *r)
 {
 	WARN_ONCE(1, "Unexpected sys_reg read to write-only register\n");
 	print_sys_reg_instr(params);
@@ -93,7 +94,7 @@ static bool access_dcsw(struct kvm_vcpu *vcpu,
 			const struct sys_reg_desc *r)
 {
 	if (!p->is_write)
-		return read_from_write_only(vcpu, p);
+		return read_from_write_only(vcpu, p, r);
 
 	kvm_set_way_flush(vcpu);
 	return true;
@@ -135,7 +136,7 @@ static bool access_gic_sgi(struct kvm_vcpu *vcpu,
 			   const struct sys_reg_desc *r)
 {
 	if (!p->is_write)
-		return read_from_write_only(vcpu, p);
+		return read_from_write_only(vcpu, p, r);
 
 	vgic_v3_dispatch_sgi(vcpu, p->regval);
 
@@ -773,7 +774,7 @@ static bool access_pmswinc(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
 		return trap_raz_wi(vcpu, p, r);
 
 	if (!p->is_write)
-		return read_from_write_only(vcpu, p);
+		return read_from_write_only(vcpu, p, r);
 
 	if (pmu_write_swinc_el0_disabled(vcpu))
 		return false;
@@ -953,7 +954,10 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 
 	{ SYS_DESC(SYS_VBAR_EL1), NULL, reset_val, VBAR_EL1, 0 },
 
+	{ SYS_DESC(SYS_ICC_EOIR0_EL1), read_from_write_only },
+	{ SYS_DESC(SYS_ICC_DIR_EL1), read_from_write_only },
 	{ SYS_DESC(SYS_ICC_SGI1R_EL1), access_gic_sgi },
+	{ SYS_DESC(SYS_ICC_EOIR1_EL1), read_from_write_only },
 	{ SYS_DESC(SYS_ICC_SRE_EL1), access_gic_sre },
 
 	{ SYS_DESC(SYS_CONTEXTIDR_EL1), access_vm_reg, reset_val, CONTEXTIDR_EL1, 0 },

virt/kvm/arm/hyp/vgic-v3-sr.c

@@ -980,6 +980,8 @@ int __hyp_text __vgic_v3_perform_cpuif_access(struct kvm_vcpu *vcpu)
 		break;
 	case SYS_ICC_EOIR0_EL1:
 	case SYS_ICC_EOIR1_EL1:
+		if (unlikely(is_read))
+			return 0;
 		fn = __vgic_v3_write_eoir;
 		break;
 	case SYS_ICC_GRPEN1_EL1:
@@ -1039,6 +1041,8 @@ int __hyp_text __vgic_v3_perform_cpuif_access(struct kvm_vcpu *vcpu)
 			fn = __vgic_v3_write_bpr0;
 		break;
 	case SYS_ICC_DIR_EL1:
+		if (unlikely(is_read))
+			return 0;
 		fn = __vgic_v3_write_dir;
 		break;
 	case SYS_ICC_RPR_EL1: