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)

7 files changed, 52 insertions, 7 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.
diff --git a/tools/libxl/libxl_create.c b/tools/libxl/libxl_create.c
index 7567238f75..c5ec577127 100644
--- a/tools/libxl/libxl_create.c
+++ b/tools/libxl/libxl_create.c
@@ -1227,7 +1227,8 @@ static void domain_create_cb(libxl__egc *egc,
 
 static int do_domain_create(libxl_ctx *ctx, libxl_domain_config *d_config,
                             uint32_t *domid,
-                            int restore_fd, const libxl_asyncop_how *ao_how,
+                            int restore_fd, int checkpointed_stream,
+                            const libxl_asyncop_how *ao_how,
                             const libxl_asyncprogress_how *aop_console_how)
 {
     AO_CREATE(ctx, 0, ao_how);
@@ -1238,6 +1239,7 @@ static int do_domain_create(libxl_ctx *ctx, libxl_domain_config *d_config,
     cdcs->dcs.guest_config = d_config;
     cdcs->dcs.restore_fd = restore_fd;
     cdcs->dcs.callback = domain_create_cb;
+    cdcs->dcs.checkpointed_stream = checkpointed_stream;
     libxl__ao_progress_gethow(&cdcs->dcs.aop_console_how, aop_console_how);
     cdcs->domid_out = domid;
 
@@ -1264,17 +1266,18 @@ int libxl_domain_create_new(libxl_ctx *ctx, libxl_domain_config *d_config,
                             const libxl_asyncop_how *ao_how,
                             const libxl_asyncprogress_how *aop_console_how)
 {
-    return do_domain_create(ctx, d_config, domid, -1,
+    return do_domain_create(ctx, d_config, domid, -1, 0,
                             ao_how, aop_console_how);
 }
 
 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)
+                                const libxl_asyncprogress_how *aop_console_how)
 {
     return do_domain_create(ctx, d_config, domid, restore_fd,
-                            ao_how, aop_console_how);
+                            params->checkpointed_stream, ao_how, aop_console_how);
 }
 
 /*
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index f051d91ed9..4e1505503c 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -2514,6 +2514,7 @@ struct libxl__domain_create_state {
     libxl_asyncprogress_how aop_console_how;
     /* private to domain_create */
     int guest_domid;
+    int checkpointed_stream;
     libxl__domain_build_state build_state;
     libxl__bootloader_state bl;
     libxl__stub_dm_spawn_state dmss;
diff --git a/tools/libxl/libxl_save_callout.c b/tools/libxl/libxl_save_callout.c
index f164e98462..6e45b2f047 100644
--- a/tools/libxl/libxl_save_callout.c
+++ b/tools/libxl/libxl_save_callout.c
@@ -60,7 +60,7 @@ void libxl__xc_domain_restore(libxl__egc *egc, libxl__domain_create_state *dcs,
         state->store_domid, state->console_port,
         state->console_domid,
         hvm, pae, superpages, no_incr_generationid,
-        cbflags,
+        cbflags, dcs->checkpointed_stream,
     };
 
     dcs->shs.ao = ao;
diff --git a/tools/libxl/libxl_save_helper.c b/tools/libxl/libxl_save_helper.c
index 772251af0c..880565e2fc 100644
--- a/tools/libxl/libxl_save_helper.c
+++ b/tools/libxl/libxl_save_helper.c
@@ -252,6 +252,7 @@ int main(int argc, char **argv)
         int superpages =           strtoul(NEXTARG,0,10);
         int no_incr_genidad =      strtoul(NEXTARG,0,10);
         unsigned cbflags =         strtoul(NEXTARG,0,10);
+        int checkpointed =         strtoul(NEXTARG,0,10);
         assert(!*++argv);
 
         helper_setcallbacks_restore(&helper_restore_callbacks, cbflags);
@@ -264,7 +265,7 @@ 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, checkpointed, &genidad,
                               &helper_restore_callbacks);
         helper_stub_restore_results(store_mfn,console_mfn,genidad,0);
         complete(r);
diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
index 049dbb50b5..b5d0b70064 100644
--- a/tools/libxl/libxl_types.idl
+++ b/tools/libxl/libxl_types.idl
@@ -259,6 +259,10 @@ libxl_domain_create_info = Struct("domain_create_info",[
     ("run_hotplug_scripts",libxl_defbool),
     ], dir=DIR_IN)
 
+libxl_domain_restore_params = Struct("domain_restore_params", [
+    ("checkpointed_stream", integer),
+    ])
+
 MemKB = UInt(64, init_val = "LIBXL_MEMKB_DEFAULT")
 
 libxl_domain_sched_params = Struct("domain_sched_params",[
diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c
index a91b42744c..cb0bf7280b 100644
--- a/tools/libxl/xl_cmdimpl.c
+++ b/tools/libxl/xl_cmdimpl.c
@@ -132,6 +132,7 @@ struct domain_create {
     int vnc;
     int vncautopass;
     int console_autoconnect;
+    int checkpointed_stream;
     const char *config_file;
     const char *extra_config; /* extra config string */
     const char *restore_file;
@@ -2064,8 +2065,11 @@ start:
     }
 
     if ( restoring ) {
+        libxl_domain_restore_params params;
+        params.checkpointed_stream = dom_info->checkpointed_stream;
         ret = libxl_domain_create_restore(ctx, &d_config,
                                           &domid, restore_fd,
+                                          &params,
                                           0, autoconnect_console_how);
         /*
          * On subsequent reboot etc we should create the domain, not
@@ -3679,6 +3683,7 @@ static void migrate_receive(int debug, int daemonize, int monitor,
     dom_info.paused = 1;
     dom_info.migrate_fd = recv_fd;
     dom_info.migration_domname_r = &migration_domname;
+    dom_info.checkpointed_stream = remus;
 
     rc = create_domain(&dom_info);
     if (rc < 0) {