[PATCH v3 4/6] iommu/arm: iommu_add_dt_pci_sideband_ids phantom handling

[Stewart Hildebrand <stewart.hildebrand@xxxxxxx>]

Handle phantom functions in iommu_add_dt_pci_sideband_ids(). Each phantom
function will have a unique requestor ID (RID)/BDF. On ARM, we need to
map/translate the RID/BDF to an AXI stream ID for each phantom function
according to the pci-iommu device tree mapping [1]. The RID/BDF -> AXI stream ID
mapping in DT could allow phantom devices (i.e. devices with phantom functions)
to use different AXI stream IDs based on the (phantom) function.

[1] 
https://www.kernel.org/doc/Documentation/devicetree/bindings/pci/pci-iommu.txt

Signed-off-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
---
v2->v3:
* new patch title (was: iommu/arm: iommu_add_dt_pci_device phantom handling)
* rework loop to reduce duplication
* s/iommu_fwspec_free(pci_to_dev(pdev))/iommu_fwspec_free(dev)/

v1->v2:
* new patch

---
 xen/drivers/passthrough/device_tree.c | 33 ++++++++++++++++-----------
 1 file changed, 20 insertions(+), 13 deletions(-)

diff --git a/xen/drivers/passthrough/device_tree.c 
b/xen/drivers/passthrough/device_tree.c
index d568166e19ec..c18ddae3e993 100644
--- a/xen/drivers/passthrough/device_tree.c
+++ b/xen/drivers/passthrough/device_tree.c
@@ -247,6 +247,7 @@ int iommu_add_dt_pci_sideband_ids(struct pci_dev *pdev)
     struct device *dev = pci_to_dev(pdev);
     const struct dt_device_node *np;
     int rc = NO_IOMMU;
+    unsigned int devfn = pdev->devfn;
 
     if ( !iommu_enabled )
         return NO_IOMMU;
@@ -271,21 +272,27 @@ int iommu_add_dt_pci_sideband_ids(struct pci_dev *pdev)
     if ( !ops->dt_xlate )
         return -EINVAL;
 
-    /*
-     * According to the Documentation/devicetree/bindings/pci/pci-iommu.txt
-     * from Linux.
-     */
-    rc = iommu_dt_pci_map_id(np, PCI_BDF(pdev->bus, pdev->devfn), "iommu-map",
-                             "iommu-map-mask", &iommu_spec.np, 
iommu_spec.args);
-    if ( rc )
-        return rc == -ENODEV ? NO_IOMMU : rc;
+    do {
+        /*
+         * According to the Documentation/devicetree/bindings/pci/pci-iommu.txt
+         * from Linux.
+         */
+        rc = iommu_dt_pci_map_id(np, PCI_BDF(pdev->bus, devfn), "iommu-map",
+                                 "iommu-map-mask", &iommu_spec.np, 
iommu_spec.args);
+        if ( rc )
+            return rc == -ENODEV ? NO_IOMMU : rc;
 
-    rc = iommu_dt_xlate(dev, &iommu_spec);
-    if ( rc < 0 )
-    {
-        iommu_fwspec_free(dev);
-        return -EINVAL;
+        rc = iommu_dt_xlate(dev, &iommu_spec);
+        if ( rc < 0 )
+        {
+            iommu_fwspec_free(dev);
+            return -EINVAL;
+        }
+
+        devfn += pdev->phantom_stride;
     }
+    while ( devfn != pdev->devfn &&
+            PCI_SLOT(devfn) == PCI_SLOT(pdev->devfn));
 
     return rc;
 }
-- 
2.40.1