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, 32 insertions, 1 deletions

diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
index 4cab2947e7..c9d9535b32 100644
--- a/tools/libxl/libxl.h
+++ b/tools/libxl/libxl.h
@@ -283,7 +283,8 @@
 
 /* API compatibility. */
 #ifdef LIBXL_API_VERSION
-#if LIBXL_API_VERSION != 0x040200 && LIBXL_API_VERSION != 0x040300
+#if LIBXL_API_VERSION != 0x040200 && LIBXL_API_VERSION != 0x040300 && \
+    LIBXL_API_VERSION != 0x040400
 #error Unknown LIBXL_API_VERSION
 #endif
 #endif
@@ -355,6 +356,14 @@
  */
 #define LIBXL_HAVE_SPICE_VDAGENT 1
 
+/*
+ * LIBXL_HAVE_DOMAIN_CREATE_RESTORE_PARAMS 1
+ *
+ * If this is defined, libxl_domain_create_restore()'s API has changed to
+ * include a params structure.
+ */
+#define LIBXL_HAVE_DOMAIN_CREATE_RESTORE_PARAMS 1
+
 /* Functions annotated with LIBXL_EXTERNAL_CALLERS_ONLY may not be
  * called from within libxl itself. Callers outside libxl, who
  * do not #include libxl_internal.h, are fine. */
@@ -578,9 +587,31 @@ int libxl_domain_create_new(libxl_ctx *ctx, libxl_domain_config *d_config,
                             LIBXL_EXTERNAL_CALLERS_ONLY;
 int libxl_domain_create_restore(libxl_ctx *ctx, libxl_domain_config *d_config,
                                 uint32_t *domid, int restore_fd,
+                                const libxl_domain_restore_params *params,
                                 const libxl_asyncop_how *ao_how,
                                 const libxl_asyncprogress_how *aop_console_how)
                                 LIBXL_EXTERNAL_CALLERS_ONLY;
+
+#if defined(LIBXL_API_VERSION) && LIBXL_API_VERSION < 0x040400
+
+int static inline libxl_domain_create_restore_0x040200(
+    libxl_ctx *ctx, libxl_domain_config *d_config,
+    uint32_t *domid, int restore_fd,
+    const libxl_asyncop_how *ao_how,
+    const libxl_asyncprogress_how *aop_console_how)
+    LIBXL_EXTERNAL_CALLERS_ONLY
+{
+    libxl_domain_restore_params params;
+    params.checkpointed_stream = 0;
+
+    return libxl_domain_create_restore(
+        ctx, d_config, domid, restore_fd, &params, ao_how, aop_console_how);
+}
+
+#define libxl_domain_create_restore libxl_domain_create_restore_0x040200
+
+#endif
+
   /* A progress report will be made via ao_console_how, of type
    * domain_create_console_available, when the domain's primary
    * console is available and can be connected to.