vm_event: Fix regression caused by b701ccc8

When xc_map_foreign_batch got deprecated reinitializing vm_event on a domain
where an event listener was previously active broke as it relied on the flag
XEN_DOMCTL_PFINFO_XTAB to indicate that the magic page is not in the physmap.
Manually check the gpfn type, add it to the physmap if needed, and only then
try to map it.

Signed-off-by: Tamas K Lengyel <tlengyel@novetta.com>
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>

diff --git a/tools/libxc/xc_vm_event.c b/tools/libxc/xc_vm_event.c
index 57abce0922b5768b9ba2fdd2236b9c34428ec575..443c73b1f9163ed4ff847806dd168e3db29e96ba 100644 (file)
--- a/tools/libxc/xc_vm_event.c
+++ b/tools/libxc/xc_vm_event.c
@@ -72,11 +72,10 @@ void *xc_vm_event_enable(xc_interface *xch, domid_t domain_id, int param,
 
     ring_pfn = pfn;
     mmap_pfn = pfn;
-    ring_page = xc_map_foreign_pages(xch, domain_id, PROT_READ | PROT_WRITE,
-                                     &mmap_pfn, 1);
-    if ( !ring_page )
+    rc1 = xc_get_pfn_type_batch(xch, domain_id, 1, &mmap_pfn);
+    if ( rc1 || mmap_pfn & XEN_DOMCTL_PFINFO_XTAB )
     {
-        /* Map failed, populate ring page */
+        /* Page not in the physmap, try to populate it */
         rc1 = xc_domain_populate_physmap_exact(xch, domain_id, 1, 0, 0,
                                               &ring_pfn);
         if ( rc1 != 0 )
@@ -84,15 +83,15 @@ void *xc_vm_event_enable(xc_interface *xch, domid_t domain_id, int param,
             PERROR("Failed to populate ring pfn\n");
             goto out;
         }
+    }
 
-        mmap_pfn = ring_pfn;
-        ring_page = xc_map_foreign_pages(xch, domain_id, PROT_READ | PROT_WRITE,
+    mmap_pfn = ring_pfn;
+    ring_page = xc_map_foreign_pages(xch, domain_id, PROT_READ | PROT_WRITE,
                                          &mmap_pfn, 1);
-        if ( !ring_page )
-        {
-            PERROR("Could not map the ring page\n");
-            goto out;
-        }
+    if ( !ring_page )
+    {
+        PERROR("Could not map the ring page\n");
+        goto out;
     }
 
     switch ( param )