VT-d: apply quirks at device setup time rather than only at boot

Accessing extended config space may not be possible at boot time, e.g.
when the memory space used by MMCFG is reserved only via ACPI tables,
but not in the E820/UEFI memory maps (which we need Dom0 to tell us
about). Consequently the change here still leaves the issue unaddressed
for systems where the extended config space remains inaccessible (due
to firmware bugs, i.e. not properly reserving the address space of
those regions).

With the respective messages now potentially getting logged more than
once, we ought to consider whether we should issue them only if we in
fact were required to do any masking (i.e. if the relevant mask bits
weren't already set).

This is CVE-2013-3495 / XSA-59.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/drivers/passthrough/vtd/extern.h
+++ b/xen/drivers/passthrough/vtd/extern.h
@@ -99,7 +99,7 @@ void platform_quirks_init(void);
 void vtd_ops_preamble_quirk(struct iommu* iommu);
 void vtd_ops_postamble_quirk(struct iommu* iommu);
 void me_wifi_quirk(struct domain *domain, u8 bus, u8 devfn, int map);
-void pci_vtd_quirk(struct pci_dev *pdev);
+void pci_vtd_quirk(const struct pci_dev *);
 int platform_supports_intremap(void);
 int platform_supports_x2apic(void);
 
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -1483,6 +1483,9 @@ static int domain_context_mapping(
         break;
     }
 
+    if ( !ret && devfn == pdev->devfn )
+        pci_vtd_quirk(pdev);
+
     return ret;
 }
 
@@ -1922,6 +1925,8 @@ static int intel_iommu_enable_device(str
     struct acpi_drhd_unit *drhd = acpi_find_matched_drhd_unit(pdev);
     int ret = drhd ? ats_device(pdev, drhd) : -ENODEV;
 
+    pci_vtd_quirk(pdev);
+
     if ( ret <= 0 )
         return ret;
 
@@ -1994,12 +1999,7 @@ static int intel_iommu_remove_device(u8 
 
 static int __hwdom_init setup_hwdom_device(u8 devfn, struct pci_dev *pdev)
 {
-    int err;
-
-    err = domain_context_mapping(pdev->domain, devfn, pdev);
-    if ( !err && devfn == pdev->devfn )
-        pci_vtd_quirk(pdev);
-    return err;
+    return domain_context_mapping(pdev->domain, devfn, pdev);
 }
 
 void clear_fault_bits(struct iommu *iommu)
--- a/xen/drivers/passthrough/vtd/quirks.c
+++ b/xen/drivers/passthrough/vtd/quirks.c
@@ -385,7 +385,7 @@ void me_wifi_quirk(struct domain *domain
  *   - This can cause system failure upon non-fatal VT-d faults
  *   - Potential security issue if malicious guest trigger VT-d faults
  */
-void __hwdom_init pci_vtd_quirk(struct pci_dev *pdev)
+void pci_vtd_quirk(const struct pci_dev *pdev)
 {
     int seg = pdev->seg;
     int bus = pdev->bus;