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, 7 insertions, 4 deletions

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);
 }
 
 /*