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[Xen-devel] [Patch v3] 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"

In the case of a regular migrate, the checkpointed_stream parameter can be
always cleared.  This will cause ctx->last_checkpoint to be unconditionally
set.  It doesn't matter if whe find a XC_SAVE_ID_LAST_CHECKPOINT chunk.

For a checkpointed migration, the parameter should be set, causing
ctx->last_checkpoint to start clear and can be set at an appropriate point in
the checkpointed stream.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CC: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
CC: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
CC: Shriram Rajagopalan <rshriram@xxxxxxxxx>

---
Changes since v2:
 * Correct logic due to the inverted name, and plub the correct information
   through from remus
Changes since v1:
 * Rename "last_checkpoint_unaware" to "checkpointed_stream" to be more
   generic yet still accurate as to the meaning and fix for the issue

---

This has been compile tested, and functionally tested with XenServer making
correct use of the new parameter in our use case requiring the bugfix in the
first place.  I am nowever not able to test xend or remus, but the code
certainly should work.
---
 tools/libxc/xc_domain_restore.c         |    3 ++-
 tools/libxc/xc_nomigrate.c              |    2 +-
 tools/libxc/xenguest.h                  |    3 ++-
 tools/libxl/libxl_save_helper.c         |    2 +-
 tools/python/xen/xend/XendCheckpoint.py |    2 +-
 tools/xcutils/xc_restore.c              |   14 +++++++++-----
 6 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/tools/libxc/xc_domain_restore.c b/tools/libxc/xc_domain_restore.c
index 63d36cd..297546c 100644
--- a/tools/libxc/xc_domain_restore.c
+++ b/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));
 
diff --git a/tools/libxc/xc_nomigrate.c b/tools/libxc/xc_nomigrate.c
index 73e7566..fb6d53e 100644
--- a/tools/libxc/xc_nomigrate.c
+++ b/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)
 {
diff --git a/tools/libxc/xenguest.h b/tools/libxc/xenguest.h
index 4714bd2..2101810 100644
--- a/tools/libxc/xenguest.h
+++ b/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);
 /**
diff --git a/tools/libxl/libxl_save_helper.c b/tools/libxl/libxl_save_helper.c
index 772251a..8f14b8b 100644
--- a/tools/libxl/libxl_save_helper.c
+++ b/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);
diff --git a/tools/python/xen/xend/XendCheckpoint.py 
b/tools/python/xen/xend/XendCheckpoint.py
index fa09757..a433ffa 100644
--- a/tools/python/xen/xend/XendCheckpoint.py
+++ b/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()
diff --git a/tools/xcutils/xc_restore.c b/tools/xcutils/xc_restore.c
index 35d725c..5ec90ac 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 )
     {
-- 
1.7.10.4


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