xen/passthrough: x86: Use INVALID_GFN rather than INVALID_MFN

A variable containing a guest frame should be compared to INVALID_GFN
and not INVALID_MFN.

Signed-off-by: Julien Grall <julien.grall@arm.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Tim Deegan <tim@xen.org>

xen/drivers/passthrough/amd/iommu_map.c

@@ -555,7 +555,7 @@ static int update_paging_mode(struct domain *d, unsigned long gfn)
     unsigned long old_root_mfn;
     struct domain_iommu *hd = dom_iommu(d);
 
-    if ( gfn == INVALID_MFN )
+    if ( gfn == INVALID_GFN )
         return -EADDRNOTAVAIL;
     ASSERT(!(gfn >> DEFAULT_DOMAIN_ADDRESS_WIDTH));
 

xen/drivers/passthrough/x86/iommu.c

@@ -61,7 +61,7 @@ int arch_iommu_populate_page_table(struct domain *d)
             unsigned long mfn = page_to_mfn(page);
             unsigned long gfn = mfn_to_gmfn(d, mfn);
 
-            if ( gfn != INVALID_MFN )
+            if ( gfn != INVALID_GFN )
             {
                 ASSERT(!(gfn >> DEFAULT_DOMAIN_ADDRESS_WIDTH));
                 BUG_ON(SHARED_M2P(gfn));