[PATCH v2] x86/PVH: PHYSDEVOP_pci_mmcfg_reserved should not blindly register a region

[Jan Beulich <jbeulich@xxxxxxxx>]

The op has a "is reserved" flag, and hence registration shouldn't
happen unilaterally.

Fixes: eb3dd90e4089 ("x86/physdev: enable PHYSDEVOP_pci_mmcfg_reserved for PVH 
Dom0")
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
v2: Don't treat XEN_PCI_MMCFG_RESERVED clear as an unregistration
    request.

--- a/xen/arch/x86/physdev.c
+++ b/xen/arch/x86/physdev.c
@@ -557,7 +557,7 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_H
 
         ret = pci_mmcfg_reserved(info.address, info.segment,
                                  info.start_bus, info.end_bus, info.flags);
-        if ( !ret && has_vpci(currd) )
+        if ( !ret && has_vpci(currd) && (info.flags & XEN_PCI_MMCFG_RESERVED) )
         {
             /*
              * For HVM (PVH) domains try to add the newly found MMCFG to the