KVM: arm64: nv: Forward SVE traps to guest hypervisor

Similar to FPSIMD traps, don't load SVE state if the guest hypervisor
has SVE traps enabled and forward the trap instead. Note that ZCR_EL2
will require some special handling, as it takes a sysreg trap to EL2
when HCR_EL2.NV = 1.
Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20240620164653.1130714-3-oliver.upton@linux.devSigned-off-by: Oliver Upton <oliver.upton@linux.dev>

arch/arm64/include/asm/kvm_emulate.h

@@ -702,5 +702,9 @@ static inline bool guest_hyp_fpsimd_traps_enabled(const struct kvm_vcpu *vcpu)
 	return __guest_hyp_cptr_xen_trap_enabled(vcpu, FPEN);
 }
 
+static inline bool guest_hyp_sve_traps_enabled(const struct kvm_vcpu *vcpu)
+{
+	return __guest_hyp_cptr_xen_trap_enabled(vcpu, ZEN);
+}
 
 #endif /* __ARM64_KVM_EMULATE_H__ */

arch/arm64/kvm/handle_exit.c

@@ -217,6 +217,9 @@ static int kvm_handle_unknown_ec(struct kvm_vcpu *vcpu)
  */
 static int handle_sve(struct kvm_vcpu *vcpu)
 {
+	if (guest_hyp_sve_traps_enabled(vcpu))
+		return kvm_inject_nested_sync(vcpu, kvm_vcpu_get_esr(vcpu));
+
 	kvm_inject_undefined(vcpu);
 	return 1;
 }

arch/arm64/kvm/hyp/include/hyp/switch.h

@@ -361,6 +361,8 @@ static bool kvm_hyp_handle_fpsimd(struct kvm_vcpu *vcpu, u64 *exit_code)
 	case ESR_ELx_EC_SVE:
 		if (!sve_guest)
 			return false;
+		if (guest_hyp_sve_traps_enabled(vcpu))
+			return false;
 		break;
 	default:
 		return false;