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

Commit 00a4b65f85 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)
master commit: 7051d5c872
master date: Thu, 10 Oct 2013 11:28:21 +0000

Backport to Xen-4.3:

As remus was not a supported feature in libxl in 4.3 and earlier, this
backport hardcodes a non-checkpointed stream from libxl, removing the need to
any playing around with the IDL and API.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
CC: Ian Jackson <Ian.Jackson@eu.citrix.com>

tools/libxc/xc_domain_restore.c

@@ -1401,7 +1401,7 @@ int xc_domain_restore(xc_interface *xch, int io_fd, uint32_t dom,
                       domid_t store_domid, unsigned int console_evtchn,
                       unsigned long *console_mfn, domid_t console_domid,
                       unsigned int hvm, unsigned int pae, int superpages,
-                      int no_incr_generationid,
+                      int no_incr_generationid, int checkpointed_stream,
                       unsigned long *vm_generationid_addr,
                       struct restore_callbacks *callbacks)
 {
@@ -1472,6 +1472,7 @@ int xc_domain_restore(xc_interface *xch, int io_fd, uint32_t dom,
 
     ctx->superpages = superpages;
     ctx->hvm = hvm;
+    ctx->last_checkpoint = !checkpointed_stream;
 
     ctxt = xc_hypercall_buffer_alloc(xch, ctxt, sizeof(*ctxt));
 

tools/libxc/xc_nomigrate.c

@@ -35,7 +35,7 @@ int xc_domain_restore(xc_interface *xch, int io_fd, uint32_t dom,
                       domid_t store_domid, unsigned int console_evtchn,
                       unsigned long *console_mfn, domid_t console_domid,
                       unsigned int hvm, unsigned int pae, int superpages,
-                      int no_incr_generationid,
+                      int no_incr_generationid, int checkpointed_stream,
                       unsigned long *vm_generationid_addr,
                       struct restore_callbacks *callbacks)
 {

tools/libxc/xenguest.h

@@ -114,6 +114,7 @@ struct restore_callbacks {
  * @parm pae non-zero if this HVM domain has PAE support enabled
  * @parm superpages non-zero to allocate guest memory with superpages
  * @parm no_incr_generationid non-zero if generation id is NOT to be incremented
+ * @parm checkpointed_stream non-zero if the far end of the stream is using checkpointing
  * @parm vm_generationid_addr returned with the address of the generation id buffer
  * @parm callbacks non-NULL to receive a callback to restore toolstack
  *       specific data
@@ -124,7 +125,7 @@ int xc_domain_restore(xc_interface *xch, int io_fd, uint32_t dom,
                       domid_t store_domid, unsigned int console_evtchn,
                       unsigned long *console_mfn, domid_t console_domid,
                       unsigned int hvm, unsigned int pae, int superpages,
-                      int no_incr_generationid,
+                      int no_incr_generationid, int checkpointed_stream,
                       unsigned long *vm_generationid_addr,
                       struct restore_callbacks *callbacks);
 /**

tools/libxl/libxl_save_helper.c

@@ -264,7 +264,7 @@ int main(int argc, char **argv)
         r = xc_domain_restore(xch, io_fd, dom, store_evtchn, &store_mfn,
                               store_domid, console_evtchn, &console_mfn,
                               console_domid, hvm, pae, superpages,
-                              no_incr_genidad, &genidad,
+                              no_incr_genidad, 0, &genidad,
                               &helper_restore_callbacks);
         helper_stub_restore_results(store_mfn,console_mfn,genidad,0);
         complete(r);

tools/python/xen/xend/XendCheckpoint.py

@@ -301,7 +301,7 @@ def restore(xd, fd, dominfo = None, paused = False, relocating = False):
 
         cmd = map(str, [xen.util.auxbin.pathTo(XC_RESTORE),
                         fd, dominfo.getDomid(),
-                        store_port, console_port, int(is_hvm), pae, apic, superpages])
+                        store_port, console_port, int(is_hvm), pae, apic, superpages, 1])
         log.debug("[xc_restore]: %s", string.join(cmd))
 
         handler = RestoreInputHandler()

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 )
     {