hw/pci/pci_host: Allow PCI host to bypass iommu

Add a new bypass_iommu property for PCI host and use it to check
whether devices attached to the PCI root bus will bypass iommu.
In pci_device_iommu_address_space(), check the property and
avoid getting iommu address space for devices bypass iommu.

Signed-off-by: Xingang Wang <wangxingang5@huawei.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Message-Id: <1625748919-52456-2-git-send-email-wangxingang5@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/pci/pci.c

@@ -416,6 +416,22 @@ const char *pci_root_bus_path(PCIDevice *dev)
     return rootbus->qbus.name;
 }
 
+bool pci_bus_bypass_iommu(PCIBus *bus)
+{
+    PCIBus *rootbus = bus;
+    PCIHostState *host_bridge;
+
+    if (!pci_bus_is_root(bus)) {
+        rootbus = pci_device_root_bus(bus->parent_dev);
+    }
+
+    host_bridge = PCI_HOST_BRIDGE(rootbus->qbus.parent);
+
+    assert(host_bridge->bus == rootbus);
+
+    return host_bridge->bypass_iommu;
+}
+
 static void pci_root_bus_init(PCIBus *bus, DeviceState *parent,
                               MemoryRegion *address_space_mem,
                               MemoryRegion *address_space_io,
@@ -2718,7 +2734,7 @@ AddressSpace *pci_device_iommu_address_space(PCIDevice *dev)
 
         iommu_bus = parent_bus;
     }
-    if (iommu_bus && iommu_bus->iommu_fn) {
+    if (!pci_bus_bypass_iommu(bus) && iommu_bus && iommu_bus->iommu_fn) {
         return iommu_bus->iommu_fn(bus, iommu_bus->iommu_opaque, devfn);
     }
     return &address_space_memory;

hw/pci/pci_host.c

@@ -222,6 +222,7 @@ const VMStateDescription vmstate_pcihost = {
 static Property pci_host_properties_common[] = {
     DEFINE_PROP_BOOL("x-config-reg-migration-enabled", PCIHostState,
                      mig_enabled, true),
+    DEFINE_PROP_BOOL("bypass-iommu", PCIHostState, bypass_iommu, false),
     DEFINE_PROP_END_OF_LIST(),
 };
 

include/hw/pci/pci.h

@@ -480,6 +480,7 @@ void pci_for_each_bus(PCIBus *bus,
 
 PCIBus *pci_device_root_bus(const PCIDevice *d);
 const char *pci_root_bus_path(PCIDevice *dev);
+bool pci_bus_bypass_iommu(PCIBus *bus);
 PCIDevice *pci_find_device(PCIBus *bus, int bus_num, uint8_t devfn);
 int pci_qdev_find_device(const char *id, PCIDevice **pdev);
 void pci_bus_get_w64_range(PCIBus *bus, Range *range);

include/hw/pci/pci_host.h

@@ -43,6 +43,7 @@ struct PCIHostState {
     uint32_t config_reg;
     bool mig_enabled;
     PCIBus *bus;
+    bool bypass_iommu;
 
     QLIST_ENTRY(PCIHostState) next;
 };