xen/vpci: fix backport of 53859596c0

Commit 53859596c0 depends on the behavioral change introduced in
ee2eb6849d that inverted the initialization of the MSI-X and header vPCI
handlers.  53859596c0 requires the header to be initialized before MSI-X.

Change the order of initialization and adjust init_msix() to carve holes
for the MSI-X tables if necessary, since it will now run after the BARs
have been possibly mapped into the domain p2m.

Fixes: 50b649c742 ("vpci/msix: improve handling of bogus MSI-X capabilities")
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

xen/drivers/vpci/header.c

@@ -1016,7 +1016,7 @@ static int cf_check init_header(struct pci_dev *pdev)
     pci_conf_write16(pdev->sbdf, PCI_COMMAND, cmd);
     return rc;
 }
-REGISTER_VPCI_INIT(init_header, VPCI_PRIORITY_MIDDLE);
+REGISTER_VPCI_INIT(init_header, VPCI_PRIORITY_HIGH);
 
 /*
  * Local variables:

xen/drivers/vpci/msix.c

@@ -790,9 +790,14 @@ static int cf_check init_msix(struct pci_dev *pdev)
     pdev->vpci->msix = msix;
     list_add(&msix->next, &d->arch.hvm.msix_tables);
 
-    return 0;
+    /*
+     * vPCI header initialization will have mapped the whole BAR into the
+     * p2m, as MSI-X capability was not yet initialized.  Crave a hole for
+     * the MSI-X table here, so that Xen can trap accesses.
+     */
+    return vpci_make_msix_hole(pdev);
 }
-REGISTER_VPCI_INIT(init_msix, VPCI_PRIORITY_HIGH);
+REGISTER_VPCI_INIT(init_msix, VPCI_PRIORITY_MIDDLE);
 
 /*
  * Local variables: