[Xen-devel] [PATCH 1/2] VT-d: don't pass bridge devices to domain_context_mapping_one()

[Jan Beulich <jbeulich@xxxxxxxx>]

When passed a non-NULL pdev, the function does an owner check when it
finds an already existing context mapping. Bridges, however, don't get
passed through to guests, and hence their owner is always going to be
Dom0, leading to the assigment of all but one of the function of multi-
function PCI devices behind bridges to fail.

Reported-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
Note: This was reported as an apparent regression from XSA-302 / -306.
      So far I haven't been able to figure out how the code would have
      worked before, i.e. to me it looks like a pre-existing problem.
      This leaves the risk of the change here papering over another
      issue.

--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -1499,7 +1499,7 @@ static int domain_context_mapping(struct
             break;
 
         ret = domain_context_mapping_one(domain, drhd->iommu, bus, devfn,
-                                         pci_get_pdev(seg, bus, devfn));
+                                         NULL);
 
         /*
          * Devices behind PCIe-to-PCI/PCIx bridge may generate different
@@ -1509,7 +1509,7 @@ static int domain_context_mapping(struct
         if ( !ret && pdev_type(seg, bus, devfn) == DEV_TYPE_PCIe2PCI_BRIDGE &&
              (secbus != pdev->bus || pdev->devfn != 0) )
             ret = domain_context_mapping_one(domain, drhd->iommu, secbus, 0,
-                                             pci_get_pdev(seg, secbus, 0));
+                                             NULL);
 
         break;
 


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