libxl: domain save: API changes for asynchrony

Change the internal and external APIs for domain save (suspend) to be
capable of asynchronous operation.  The implementation remains
synchronous.  The interfaces surrounding device model saving are still
synchronous.

Public API changes:

 * libxl_domain_save takes an ao_how.

 * libxl_domain_remus_start takes an ao_how.  If the
   libxl_domain_remus_info is NULL, we abort rather than returning an
   error.

 * The `suspend_callback' function passed to libxl_domain_save is
   never called by the existing implementation in libxl.  Abolish it.

 * libxl_domain_save takes its flags parameter as an argument.
   Thus libxl_domain_suspend_info is abolished.

 * XL_SUSPEND_* flags renamed to LIBXL_SAVE_*.

 * Callers in xl updated.

Internal code restructuring:

 * libxl__domain_suspend_state member types and names rationalised.

 * libxl__domain_suspend renamed from libxl__domain_suspend_common.
   (_common here actually meant "internal function").

 * libxl__domain_suspend takes a libxl__domain_suspend_state, which
   where the parameters to the operation are filled in by the caller.

 * xc_domain_save is now called via libxl__xc_domain_save which can
   itself become asynchronous.

 * Consequently, libxl__domain_suspend is split into two functions at
   the callback boundary; the second half is
   libxl__xc_domain_save_done.

 * libxl__domain_save_device_model is now called by the actual
   implementation rather than by the public wrapper.  It is already in
   its proper place in the domain save execution sequence.  So
   officially make it part of that execution sequence, renaming it to
   domain_save_device_model.

 * Effectively, rewrite the public wrapper functions
   libxl_domain_suspend and libxl_domain_remus_start.

 * Remove a needless #include <xenctrl.h>

 * libxl__domain_suspend aborts on unexpected domain types rather
   than mysteriously returning EINVAL.

 * struct save_callbacks moved from the stack to the dss.

Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>

1 files changed, 37 insertions, 8 deletions

diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 7a3b7f8722..1ee5bd2b09 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -1777,16 +1777,28 @@ _hidden int libxl__datacopier_start(libxl__datacopier_state *dc);
 
 typedef struct libxl__domain_suspend_state libxl__domain_suspend_state;
 
+typedef void libxl__domain_suspend_cb(libxl__egc*,
+                                      libxl__domain_suspend_state*, int rc);
+
 struct libxl__domain_suspend_state {
-    libxl__gc *gc;
+    /* set by caller of libxl__domain_suspend */
+    libxl__ao *ao;
+    libxl__domain_suspend_cb *callback;
+
+    uint32_t domid;
+    int fd;
+    libxl_domain_type type;
+    int live;
+    int debug;
+    const libxl_domain_remus_info *remus;
+    /* private */
     xc_evtchn *xce; /* event channel handle */
     int suspend_eventchn;
-    int domid;
     int hvm;
-    unsigned int xcflags;
+    int xcflags;
     int guest_responded;
-    int save_fd; /* Migration stream fd (for Remus) */
     int interval; /* checkpoint interval (for Remus) */
+    struct save_callbacks callbacks;
 };
 
 
@@ -1903,10 +1915,27 @@ struct libxl__domain_create_state {
 
 /*----- Domain suspend (save) functions -----*/
 
-_hidden int libxl__domain_suspend_common(libxl__gc *gc, uint32_t domid, int fd,
-                                         libxl_domain_type type,
-                                         int live, int debug,
-                                         const libxl_domain_remus_info *r_info);
+/* calls dss->callback when done */
+_hidden void libxl__domain_suspend(libxl__egc *egc,
+                                   libxl__domain_suspend_state *dss);
+
+
+/* calls libxl__xc_domain_suspend_done when done */
+_hidden void libxl__xc_domain_save(libxl__egc*, libxl__domain_suspend_state*,
+                                   unsigned long vm_generationid_addr);
+/* If rc==0 then retval is the return value from xc_domain_save
+ * and errnoval is the errno value it provided.
+ * If rc!=0, retval and errnoval are undefined. */
+_hidden void libxl__xc_domain_save_done(libxl__egc*,
+                                        libxl__domain_suspend_state*,
+                                        int rc, int retval, int errnoval);
+
+_hidden int libxl__domain_suspend_common_callback(void *data);
+_hidden int libxl__domain_suspend_common_switch_qemu_logdirty
+                               (int domid, unsigned int enable, void *data);
+_hidden int libxl__toolstack_save(uint32_t domid, uint8_t **buf,
+        uint32_t *len, void *data);
+
 
 /* calls libxl__xc_domain_restore_done when done */
 _hidden void libxl__xc_domain_restore(libxl__egc *egc,