AMD/IOMMU: restore DTE fields in amd_iommu_setup_domain_device()

Commit 1b00c16bdf ("AMD/IOMMU: pre-fill all DTEs right after table
allocation") moved ourselves into a more secure default state, but
didn't take sufficient care to also undo the effects when handing a
previously disabled device back to a(nother) domain. Put the fields
that may have been changed elsewhere back to their intended values
(some fields amd_iommu_disable_domain_device() touches don't
currently get written anywhere else, and hence don't need modifying
here).

Reported-by: Sander Eikelenboom <linux@eikelenboom.it>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Tested-by: Igor Druzhinin <igor.druzhinin@citrix.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
Release-acked-by: Juergen Gross <jgross@suse.com>

xen/drivers/passthrough/amd/pci_amd_iommu.c

@@ -114,11 +114,21 @@ static void amd_iommu_setup_domain_device(
 
     if ( !dte->v || !dte->tv )
     {
+        const struct ivrs_mappings *ivrs_dev;
+
         /* bind DTE to domain page-tables */
         amd_iommu_set_root_page_table(
             dte, page_to_maddr(hd->arch.root_table), domain->domain_id,
             hd->arch.paging_mode, valid);
 
+        /* Undo what amd_iommu_disable_domain_device() may have done. */
+        ivrs_dev = &get_ivrs_mappings(iommu->seg)[req_id];
+        if ( dte->it_root )
+            dte->int_ctl = IOMMU_DEV_TABLE_INT_CONTROL_TRANSLATED;
+        dte->iv = iommu_intremap;
+        dte->ex = ivrs_dev->dte_allow_exclusion;
+        dte->sys_mgt = MASK_EXTR(ivrs_dev->device_flags, ACPI_IVHD_SYSTEM_MGMT);
+
         if ( pci_ats_device(iommu->seg, bus, pdev->devfn) &&
              iommu_has_cap(iommu, PCI_CAP_IOTLB_SHIFT) )
             dte->i = ats_enabled;