Intel IOMMU功能介绍

# acpidump --table DMAR -b > dmar.out
# iasl -d dmar.out
# cat dmar.dsl

/**
 * dmar_table_detect - checks to see if the platform supports DMAR devices
 */
static int __init dmar_table_detect(void)
{
        acpi_status status = AE_OK;

        /* if we could find DMAR table, then there are DMAR devices */
        status = acpi_get_table(ACPI_SIG_DMAR, 0, &dmar_tbl);

        if (ACPI_SUCCESS(status) && !dmar_tbl) {
                pr_warn("Unable to map DMAR\n");
                status = AE_NOT_FOUND;
        }

        return ACPI_SUCCESS(status) ? 0 : -ENOENT;
}

    intel_iommu_init
        |-> dmar_table_init -> parse_dmar_table -> dmar_walk_dmar_table //重点分析
        |-> dmar_dev_scope_init
            |-> dmar_acpi_dev_scope_init -> dmar_acpi_insert_dev_scope  //重点分析
            |-> dmar_pci_bus_add_dev -> dmar_insert_dev_scope
            |-> bus_register_notifier
        |-> dmar_init_reserved_ranges   // init RMRR
        |-> init_no_remapping_devices   // init no remapping devices
        |-> init_dmars  //重点分析
        |-> dma_ops = &intel_dma_ops
        |-> iommu_device_sysfs_add, iommu_device_set_ops, iommu_device_register
        |-> bus_set_iommu(&pci_bus_type, &intel_iommu_ops)
        |-> bus_register_notifier(&pci_bus_type, &device_nb)

static int __init
parse_dmar_table(void)
{
    struct acpi_table_dmar *dmar;
    int drhd_count = 0;
    int ret;
    struct dmar_res_callback cb = {
        .print_entry = true,
        .ignore_unhandled = true,
        .arg[ACPI_DMAR_TYPE_HARDWARE_UNIT] = &drhd_count,
        .cb[ACPI_DMAR_TYPE_HARDWARE_UNIT] = &dmar_parse_one_drhd,
        .cb[ACPI_DMAR_TYPE_RESERVED_MEMORY] = &dmar_parse_one_rmrr,
        .cb[ACPI_DMAR_TYPE_ROOT_ATS] = &dmar_parse_one_atsr,
        .cb[ACPI_DMAR_TYPE_HARDWARE_AFFINITY] = &dmar_parse_one_rhsa,
        .cb[ACPI_DMAR_TYPE_NAMESPACE] = &dmar_parse_one_andd,
    };

    /*
     * Do it again, earlier dmar_tbl mapping could be mapped with
     * fixed map.
     */
    dmar_table_detect();    // 重新detect dmar table

    /*
     * ACPI tables may not be DMA protected by tboot, so use DMAR copy
     * SINIT saved in SinitMleData in TXT heap (which is DMA protected)
     */
    dmar_tbl = tboot_get_dmar_table(dmar_tbl);

    dmar = (struct acpi_table_dmar *)dmar_tbl;
    if (!dmar)
        return -ENODEV;

    if (dmar->width < PAGE_SHIFT - 1) {
        pr_warn("Invalid DMAR haw\n");
        return -EINVAL;
    }

    pr_info("Host address width %d\n", dmar->width + 1);
    ret = dmar_walk_dmar_table(dmar, &cb);  //遍历ACPI表完成解析
    if (ret == 0 && drhd_count == 0)
        pr_warn(FW_BUG "No DRHD structure found in DMAR table\n");

    return ret;
}

static void __init dmar_acpi_insert_dev_scope(u8 device_number,
                          struct acpi_device *adev)
{
    struct dmar_drhd_unit *dmaru;
    struct acpi_dmar_hardware_unit *drhd;
    struct acpi_dmar_device_scope *scope;
    struct device *tmp;
    int i;
    struct acpi_dmar_pci_path *path;

    for_each_drhd_unit(dmaru) {
        drhd = container_of(dmaru->hdr,
                    struct acpi_dmar_hardware_unit,
                    header);

        for (scope = (void *)(drhd + 1);
             (unsigned long)scope < ((unsigned long)drhd) + drhd->header.length;
             scope = ((void *)scope) + scope->length) {
            if (scope->entry_type != ACPI_DMAR_SCOPE_TYPE_NAMESPACE)
                continue;
            if (scope->enumeration_id != device_number)
                continue;

            path = (void *)(scope + 1);
            pr_info("ACPI device \"%s\" under DMAR at %llx as %02x:%02x.%d\n",
                dev_name(&adev->dev), dmaru->reg_base_addr,
                scope->bus, path->device, path->function);
            for_each_dev_scope(dmaru->devices, dmaru->devices_cnt, i, tmp)
                if (tmp == NULL) {
                    dmaru->devices[i].bus = scope->bus;
                    dmaru->devices[i].devfn = PCI_DEVFN(path->device,
                                        path->function);
                    rcu_assign_pointer(dmaru->devices[i].dev,
                               get_device(&adev->dev));
                    return;
                }
            BUG_ON(i >= dmaru->devices_cnt);
        }
    }
    pr_warn("No IOMMU scope found for ANDD enumeration ID %d (%s)\n",
        device_number, dev_name(&adev->dev));
}

        init_dmars
                |-> intel_iommu_init_qi         // qeueu invalidation
                |-> iommu_init_domains
                |-> init_translation_status
                |-> iommu_alloc_root_entry      //创建Root Entry
                |-> translation_pre_enabled
                |-> iommu_set_root_entry
                |-> iommu_prepare_rmrr_dev
                |-> iommu_prepare_isa           // 0-16MiB 留给ISA设备
                |-> dmar_set_interrupt          // IOMMU中断初始化