xend: reserve vtd_mem on guest restore

There's need for free vtd_mem more memory for guest with
xen-unstable c/s 17529.  This memory is freed when guest is
created, but is not freed when guest is restored. So restore
guest fails due  to not enough of memory for guest.

Following patch uses same calculation of memory to free in guest
restore as is in guest creation.

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>

tools/python/xen/xend/XendCheckpoint.py

@@ -277,7 +277,15 @@ def restore(xd, fd, dominfo = None, paused = False, relocating = False):
         # set memory limit
         xc.domain_setmaxmem(dominfo.getDomid(), maxmem)
 
-        balloon.free(memory + shadow, dominfo)
+        vtd_mem = 0
+        info = xc.physinfo()
+        if 'hvm_directio' in info['virt_caps']:
+            # Reserve 1 page per MiB of RAM for separate VT-d page table.
+            vtd_mem = 4 * (dominfo.info['memory_static_max'] / 1024 / 1024)
+            # Round vtd_mem up to a multiple of a MiB.
+            vtd_mem = ((vtd_mem + 1023) / 1024) * 1024
+
+        balloon.free(memory + shadow + vtd_mem, dominfo)
 
         shadow_cur = xc.shadow_mem_control(dominfo.getDomid(), shadow / 1024)
         dominfo.info['shadow_memory'] = shadow_cur