iommu/s390: implement iommu passthrough via identity domain

Enabled via the kernel command-line 'iommu.passthrough=1' option.

Introduce the concept of identity domains to s390-iommu, which relies on
the bus_dma_region to offset identity mappings to the start of the DMA
aperture advertized by CLP.

Tested-by: Niklas Schnelle <schnelle@linux.ibm.com>
Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20250212213418.182902-5-mjrosato@linux.ibm.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

diff --git a/drivers/iommu/s390-iommu.c b/drivers/iommu/s390-iommu.c
index 007ccfdad4954dcb0d4b27938eeed81daa1a636c..e1c76e0f9c2b7f9e32e3d8586a5112fe0a319f36 100644 (file)
--- a/drivers/iommu/s390-iommu.c
+++ b/drivers/iommu/s390-iommu.c
@@ -16,7 +16,7 @@
 
 #include "dma-iommu.h"
 
-static const struct iommu_ops s390_iommu_ops;
+static const struct iommu_ops s390_iommu_ops, s390_iommu_rtr_ops;
 
 static struct kmem_cache *dma_region_table_cache;
 static struct kmem_cache *dma_page_table_cache;
@@ -432,9 +432,11 @@ static int blocking_domain_attach_device(struct iommu_domain *domain,
                return 0;
 
        s390_domain = to_s390_domain(zdev->s390_domain);
-       spin_lock_irqsave(&s390_domain->list_lock, flags);
-       list_del_rcu(&zdev->iommu_list);
-       spin_unlock_irqrestore(&s390_domain->list_lock, flags);
+       if (zdev->dma_table) {
+               spin_lock_irqsave(&s390_domain->list_lock, flags);
+               list_del_rcu(&zdev->iommu_list);
+               spin_unlock_irqrestore(&s390_domain->list_lock, flags);
+       }
 
        zpci_unregister_ioat(zdev, 0);
        zdev->dma_table = NULL;
@@ -762,7 +764,13 @@ int zpci_init_iommu(struct zpci_dev *zdev)
        if (rc)
                goto out_err;
 
-       rc = iommu_device_register(&zdev->iommu_dev, &s390_iommu_ops, NULL);
+       if (zdev->rtr_avail) {
+               rc = iommu_device_register(&zdev->iommu_dev,
+                                          &s390_iommu_rtr_ops, NULL);
+       } else {
+               rc = iommu_device_register(&zdev->iommu_dev, &s390_iommu_ops,
+                                          NULL);
+       }
        if (rc)
                goto out_sysfs;
 
@@ -826,6 +834,39 @@ static int __init s390_iommu_init(void)
 }
 subsys_initcall(s390_iommu_init);
 
+static int s390_attach_dev_identity(struct iommu_domain *domain,
+                                   struct device *dev)
+{
+       struct zpci_dev *zdev = to_zpci_dev(dev);
+       u8 status;
+       int cc;
+
+       blocking_domain_attach_device(&blocking_domain, dev);
+
+       /* If we fail now DMA remains blocked via blocking domain */
+       cc = s390_iommu_domain_reg_ioat(zdev, domain, &status);
+
+       /*
+        * If the device is undergoing error recovery the reset code
+        * will re-establish the new domain.
+        */
+       if (cc && status != ZPCI_PCI_ST_FUNC_NOT_AVAIL)
+               return -EIO;
+
+       zdev_s390_domain_update(zdev, domain);
+
+       return 0;
+}
+
+static const struct iommu_domain_ops s390_identity_ops = {
+       .attach_dev = s390_attach_dev_identity,
+};
+
+static struct iommu_domain s390_identity_domain = {
+       .type = IOMMU_DOMAIN_IDENTITY,
+       .ops = &s390_identity_ops,
+};
+
 static struct iommu_domain blocking_domain = {
        .type = IOMMU_DOMAIN_BLOCKED,
        .ops = &(const struct iommu_domain_ops) {
@@ -833,23 +874,31 @@ static struct iommu_domain blocking_domain = {
        }
 };
 
-static const struct iommu_ops s390_iommu_ops = {
-       .blocked_domain         = &blocking_domain,
-       .release_domain         = &blocking_domain,
-       .capable = s390_iommu_capable,
-       .domain_alloc_paging = s390_domain_alloc_paging,
-       .probe_device = s390_iommu_probe_device,
-       .device_group = generic_device_group,
-       .pgsize_bitmap = SZ_4K,
-       .get_resv_regions = s390_iommu_get_resv_regions,
-       .default_domain_ops = &(const struct iommu_domain_ops) {
-               .attach_dev     = s390_iommu_attach_device,
-               .map_pages      = s390_iommu_map_pages,
-               .unmap_pages    = s390_iommu_unmap_pages,
-               .flush_iotlb_all = s390_iommu_flush_iotlb_all,
-               .iotlb_sync      = s390_iommu_iotlb_sync,
-               .iotlb_sync_map  = s390_iommu_iotlb_sync_map,
-               .iova_to_phys   = s390_iommu_iova_to_phys,
-               .free           = s390_domain_free,
+#define S390_IOMMU_COMMON_OPS() \
+       .blocked_domain         = &blocking_domain, \
+       .release_domain         = &blocking_domain, \
+       .capable = s390_iommu_capable, \
+       .domain_alloc_paging = s390_domain_alloc_paging, \
+       .probe_device = s390_iommu_probe_device, \
+       .device_group = generic_device_group, \
+       .pgsize_bitmap = SZ_4K, \
+       .get_resv_regions = s390_iommu_get_resv_regions, \
+       .default_domain_ops = &(const struct iommu_domain_ops) { \
+               .attach_dev     = s390_iommu_attach_device, \
+               .map_pages      = s390_iommu_map_pages, \
+               .unmap_pages    = s390_iommu_unmap_pages, \
+               .flush_iotlb_all = s390_iommu_flush_iotlb_all, \
+               .iotlb_sync      = s390_iommu_iotlb_sync, \
+               .iotlb_sync_map  = s390_iommu_iotlb_sync_map, \
+               .iova_to_phys   = s390_iommu_iova_to_phys, \
+               .free           = s390_domain_free, \
        }
+
+static const struct iommu_ops s390_iommu_ops = {
+       S390_IOMMU_COMMON_OPS()
+};
+
+static const struct iommu_ops s390_iommu_rtr_ops = {
+       .identity_domain        = &s390_identity_domain,
+       S390_IOMMU_COMMON_OPS()
 };