tools/migrate: Fix regression when migrating from older version of Xen

Commit 00a4b65f8534c9e6521eab2e6ce796ae36037774 Sep 7 2010
  "libxc: provide notification of final checkpoint to restore end"
broke migration from any version of Xen using tools from prior to that commit

Older tools have no idea about an XC_SAVE_ID_LAST_CHECKPOINT, causing newer
tools xc_domain_restore() to start reading the qemu save record, as
ctx->last_checkpoint is 0.

The failure looks like:
  xc: error: Max batch size exceeded (1970103633). Giving up.
where 1970103633 = 0x756d6551 = *(uint32_t*)"Qemu"

With this fix in place, the behaviour for normal migrations is reverted to how
it was before the regression; the migration is considered non-checkpointed
right from the start.  A XC_SAVE_ID_LAST_CHECKPOINT chunk seen in the
migration stream is a nop.  For checkpointed migrations the behaviour is
unchanged.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Ian Campbell <Ian.Campbell@citrix.com>
CC: Ian Jackson <Ian.Jackson@eu.citrix.com>
Acked-by: Shriram Rajagopalan <rshriram@cs.ubc.ca> (Remus bits)

1 files changed, 9 insertions, 5 deletions

diff --git a/tools/xcutils/xc_restore.c b/tools/xcutils/xc_restore.c
index 35d725c6cb..5ec90ac8ad 100644
--- a/tools/xcutils/xc_restore.c
+++ b/tools/xcutils/xc_restore.c
@@ -19,7 +19,7 @@ int
 main(int argc, char **argv)
 {
     unsigned int domid, store_evtchn, console_evtchn;
-    unsigned int hvm, pae, apic, lflags;
+    unsigned int hvm, pae, apic, lflags, checkpointed;
     xc_interface *xch;
     int io_fd, ret;
     int superpages;
@@ -27,9 +27,9 @@ main(int argc, char **argv)
     xentoollog_level lvl;
     xentoollog_logger *l;
 
-    if ( (argc != 8) && (argc != 9) )
+    if ( !( argc >= 8 && argc <= 10) )
         errx(1, "usage: %s iofd domid store_evtchn "
-             "console_evtchn hvm pae apic [superpages]", argv[0]);
+             "console_evtchn hvm pae apic [superpages [checkpointed]]", argv[0]);
 
     lvl = XTL_DETAIL;
     lflags = XTL_STDIOSTREAM_SHOW_PID | XTL_STDIOSTREAM_HIDE_PROGRESS;
@@ -45,14 +45,18 @@ main(int argc, char **argv)
     hvm  = atoi(argv[5]);
     pae  = atoi(argv[6]);
     apic = atoi(argv[7]);
-    if ( argc == 9 )
+    if ( argc >= 9 )
 	    superpages = atoi(argv[8]);
     else
 	    superpages = !!hvm;
+    if ( argc >= 10 )
+        checkpointed = atoi(argv[9]);
+    else
+        checkpointed = 0;
 
     ret = xc_domain_restore(xch, io_fd, domid, store_evtchn, &store_mfn, 0,
                             console_evtchn, &console_mfn, 0, hvm, pae, superpages,
-                            0, NULL, NULL);
+                            0, checkpointed, NULL, NULL);
 
     if ( ret == 0 )
     {