--- a/xen/drivers/passthrough/vtd/extern.h
+++ b/xen/drivers/passthrough/vtd/extern.h
@@ -85,7 +85,7 @@ int domain_context_mapping_one(struct do
                                const struct pci_dev *pdev, domid_t domid,
                                paddr_t pgd_maddr, unsigned int mode);
 int domain_context_unmap_one(struct domain *domain, struct vtd_iommu *iommu,
-                             uint8_t bus, uint8_t devfn, domid_t domid);
+                             uint8_t bus, uint8_t devfn);
 int cf_check intel_iommu_get_reserved_device_memory(
     iommu_grdm_t *func, void *ctxt);
 
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -1533,7 +1533,7 @@ int domain_context_mapping_one(
                 check_cleanup_domid_map(domain, pdev, iommu);
             printk(XENLOG_ERR
                    "%pp: unexpected context entry %016lx_%016lx (expected %016lx_%016lx)\n",
-                   &PCI_SBDF3(pdev->seg, pdev->bus, devfn),
+                   &PCI_SBDF3(seg, bus, devfn),
                    (uint64_t)(res >> 64), (uint64_t)res,
                    (uint64_t)(old >> 64), (uint64_t)old);
             rc = -EILSEQ;
@@ -1601,9 +1601,14 @@ int domain_context_mapping_one(
 
     if ( rc )
     {
-        if ( !prev_dom )
-            ret = domain_context_unmap_one(domain, iommu, bus, devfn,
-                                           DEVICE_DOMID(domain, pdev));
+        if ( !prev_dom ||
+             /*
+              * Unmapping here means DEV_TYPE_PCI devices with RMRRs (if such
+              * exist) would cause problems if such a region was actually
+              * accessed.
+              */
+             (prev_dom == dom_io && !pdev) )
+            ret = domain_context_unmap_one(domain, iommu, bus, devfn);
         else if ( prev_dom != domain ) /* Avoid infinite recursion. */
             ret = domain_context_mapping_one(prev_dom, iommu, bus, devfn, pdev,
                                              DEVICE_DOMID(prev_dom, pdev),
@@ -1744,7 +1749,9 @@ static int domain_context_mapping(struct
          * Strictly speaking if the device is the only one behind this bridge
          * and the only one with this (secbus,0,0) tuple, it could be allowed
          * to be re-assigned regardless of RMRR presence.  But let's deal with
-         * that case only if it is actually found in the wild.
+         * that case only if it is actually found in the wild.  Note that
+         * dealing with this just here would still not render the operation
+         * secure.
          */
         else if ( prev_present && (mode & MAP_WITH_RMRR) &&
                   domain != pdev->domain )
@@ -1809,7 +1816,7 @@ static int domain_context_mapping(struct
 int domain_context_unmap_one(
     struct domain *domain,
     struct vtd_iommu *iommu,
-    uint8_t bus, uint8_t devfn, domid_t domid)
+    uint8_t bus, uint8_t devfn)
 {
     struct context_entry *context, *context_entries;
     u64 maddr;
@@ -1867,7 +1874,8 @@ int domain_context_unmap_one(
     unmap_vtd_domain_page(context_entries);
 
     if ( !iommu->drhd->segment && !rc )
-        rc = me_wifi_quirk(domain, bus, devfn, domid, 0, UNMAP_ME_PHANTOM_FUNC);
+        rc = me_wifi_quirk(domain, bus, devfn, DOMID_INVALID, 0,
+                           UNMAP_ME_PHANTOM_FUNC);
 
     if ( rc && !is_hardware_domain(domain) && domain != dom_io )
     {
@@ -1916,8 +1924,7 @@ static const struct acpi_drhd_unit *doma
         if ( iommu_debug )
             printk(VTDPREFIX "%pd:PCIe: unmap %pp\n",
                    domain, &PCI_SBDF3(seg, bus, devfn));
-        ret = domain_context_unmap_one(domain, iommu, bus, devfn,
-                                       DEVICE_DOMID(domain, pdev));
+        ret = domain_context_unmap_one(domain, iommu, bus, devfn);
         if ( !ret && devfn == pdev->devfn && ats_device(pdev, drhd) > 0 )
             disable_ats_device(pdev);
 
@@ -1930,8 +1937,7 @@ static const struct acpi_drhd_unit *doma
         if ( iommu_debug )
             printk(VTDPREFIX "%pd:PCI: unmap %pp\n",
                    domain, &PCI_SBDF3(seg, bus, devfn));
-        ret = domain_context_unmap_one(domain, iommu, bus, devfn,
-                                       DEVICE_DOMID(domain, pdev));
+        ret = domain_context_unmap_one(domain, iommu, bus, devfn);
         if ( ret )
             break;
 
@@ -1954,12 +1960,10 @@ static const struct acpi_drhd_unit *doma
             break;
         }
 
-        ret = domain_context_unmap_one(domain, iommu, tmp_bus, tmp_devfn,
-                                       DEVICE_DOMID(domain, pdev));
+        ret = domain_context_unmap_one(domain, iommu, tmp_bus, tmp_devfn);
         /* PCIe to PCI/PCIx bridge */
         if ( !ret && pdev_type(seg, tmp_bus, tmp_devfn) == DEV_TYPE_PCIe2PCI_BRIDGE )
-            ret = domain_context_unmap_one(domain, iommu, secbus, 0,
-                                           DEVICE_DOMID(domain, pdev));
+            ret = domain_context_unmap_one(domain, iommu, secbus, 0);
 
         break;
 
--- a/xen/drivers/passthrough/vtd/quirks.c
+++ b/xen/drivers/passthrough/vtd/quirks.c
@@ -427,7 +427,7 @@ static int __must_check map_me_phantom_f
                                         domid, pgd_maddr, mode);
     else
         rc = domain_context_unmap_one(domain, drhd->iommu, 0,
-                                      PCI_DEVFN(dev, 7), domid);
+                                      PCI_DEVFN(dev, 7));
 
     return rc;
 }
