[RFC 2/7] hw/pci: Introduce pci_device_iommu_bus

[Eric Auger <eric.auger@redhat.com>]

This helper will allow subsequent patches to retrieve the IOMMU bus
and call its associated PCIIOMMUOps callbacks.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
---
 include/hw/pci/pci.h |  1 +
 hw/pci/pci.c         | 16 ++++++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
index 63c018b35a..649b327f9f 100644
--- a/include/hw/pci/pci.h
+++ b/include/hw/pci/pci.h
@@ -403,6 +403,7 @@ typedef struct PCIIOMMUOps {
 } PCIIOMMUOps;
 
 AddressSpace *pci_device_iommu_address_space(PCIDevice *dev);
+PCIBus *pci_device_iommu_bus(PCIDevice *dev);
 
 /**
  * pci_setup_iommu: Initialize specific IOMMU handlers for a PCIBus
diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index 76080af580..5bf07662fe 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -2672,6 +2672,22 @@ static void pci_device_class_base_init(ObjectClass *klass, void *data)
     }
 }
 
+PCIBus *pci_device_iommu_bus(PCIDevice *dev)
+{
+    PCIBus *bus = pci_get_bus(dev);
+    PCIBus *iommu_bus = bus;
+
+    while (iommu_bus && !iommu_bus->iommu_ops && iommu_bus->parent_dev) {
+        PCIBus *parent_bus = pci_get_bus(iommu_bus->parent_dev);
+
+        iommu_bus = parent_bus;
+    }
+    if (pci_bus_bypass_iommu(bus)) {
+        return NULL;
+    }
+    return iommu_bus;
+}
+
 AddressSpace *pci_device_iommu_address_space(PCIDevice *dev)
 {
     PCIBus *bus = pci_get_bus(dev);
-- 
2.41.0