get_perf_reg_address
iommu_pmu->cfg_reg = get_perf_reg_address(iommu, DMAR_PERFCFGOFF_REG);
iommu_pmu->cntr_reg = get_perf_reg_address(iommu, DMAR_PERFCNTROFF_REG);
iommu_pmu->overflow = get_perf_reg_address(iommu, DMAR_PERFOVFOFF_REG);