kvm_write_reg
kvm_write_reg(vcpu, LOONGARCH_GPR_A0, run->hypercall.ret);
kvm_write_reg(vcpu, LOONGARCH_GPR_A0, ret);
kvm_write_reg(vcpu, LOONGARCH_GPR_A0, KVM_HCALL_INVALID_CODE);
kvm_write_reg(vcpu, LOONGARCH_GPR_A0, KVM_HCALL_INVALID_CODE);