3 files changed, 34 insertions, 0 deletions

diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index 297196b242..c3df9d6656 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -2912,6 +2912,19 @@ static void pci_device_get_iommu_bus_devfn(PCIDevice *dev,
             }
         }
 
+        /*
+         * When multiple PCI Express Root Buses are defined using pxb-pcie,
+         * the IOMMU configuration may be specific to each root bus. However,
+         * pxb-pcie acts as a special root complex whose parent is effectively
+         * the default root complex(pcie.0). Ensure that we retrieve the
+         * correct IOMMU ops(if any) in such cases.
+         */
+        if (pci_bus_is_express(iommu_bus) && pci_bus_is_root(iommu_bus)) {
+            if (parent_bus->iommu_per_bus) {
+                break;
+            }
+        }
+
         iommu_bus = parent_bus;
     }
 
@@ -3172,6 +3185,24 @@ void pci_setup_iommu(PCIBus *bus, const PCIIOMMUOps *ops, void *opaque)
     bus->iommu_opaque = opaque;
 }
 
+/*
+ * Similar to pci_setup_iommu(), but sets iommu_per_bus to true,
+ * indicating that the IOMMU is specific to this bus. This is used by
+ * IOMMU implementations that are tied to a specific PCIe root complex.
+ *
+ * In QEMU, pxb-pcie behaves as a special root complex whose parent is
+ * effectively the default root complex (pcie.0). The iommu_per_bus
+ * is checked in pci_device_get_iommu_bus_devfn() to ensure the correct
+ * IOMMU ops are returned, avoiding the use of the parent’s IOMMU when
+ * it's not appropriate.
+ */
+void pci_setup_iommu_per_bus(PCIBus *bus, const PCIIOMMUOps *ops,
+                             void *opaque)
+{
+    pci_setup_iommu(bus, ops, opaque);
+    bus->iommu_per_bus = true;
+}
+
 static void pci_dev_get_w64(PCIBus *b, PCIDevice *dev, void *opaque)
 {
     Range *range = opaque;
diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
index 6b7d3ac8a3..6bccb25ac2 100644
--- a/include/hw/pci/pci.h
+++ b/include/hw/pci/pci.h
@@ -773,6 +773,8 @@ int pci_iommu_unregister_iotlb_notifier(PCIDevice *dev, uint32_t pasid,
  */
 void pci_setup_iommu(PCIBus *bus, const PCIIOMMUOps *ops, void *opaque);
 
+void pci_setup_iommu_per_bus(PCIBus *bus, const PCIIOMMUOps *ops, void *opaque);
+
 pcibus_t pci_bar_address(PCIDevice *d,
                          int reg, uint8_t type, pcibus_t size);
 
diff --git a/include/hw/pci/pci_bus.h b/include/hw/pci/pci_bus.h
index 2261312546..c738446788 100644
--- a/include/hw/pci/pci_bus.h
+++ b/include/hw/pci/pci_bus.h
@@ -35,6 +35,7 @@ struct PCIBus {
     enum PCIBusFlags flags;
     const PCIIOMMUOps *iommu_ops;
     void *iommu_opaque;
+    bool iommu_per_bus;
     uint8_t devfn_min;
     uint32_t slot_reserved_mask;
     pci_set_irq_fn set_irq;