[PATCH v1 05/12] libxl: add new hotplug interface support to hotplug script callers

[Roger Pau Monne <roger.pau@citrix.com>]

Add support to call hotplug scripts that use the new hotplug interface
to the low-level functions in charge of calling hotplug scripts.

libxl__prepare_ao_device sets the hotplug version to 1, in later
patches hotplug version will be set to 2 by the caller to use this
new hotplug calling convention.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
---
 tools/libxl/libxl_device.c           |   14 +++++++-
 tools/libxl/libxl_internal.h         |   22 ++++++++++++
 tools/libxl/libxl_linux.c            |   61 +++++++++++++++++++++++++--------
 tools/libxl/libxl_types_internal.idl |    5 +++
 4 files changed, 86 insertions(+), 16 deletions(-)

diff --git a/tools/libxl/libxl_device.c b/tools/libxl/libxl_device.c
index 044cac5..904853a 100644
--- a/tools/libxl/libxl_device.c
+++ b/tools/libxl/libxl_device.c
@@ -83,6 +83,12 @@ out:
     return rc;
 }
 
+char *libxl__device_xs_hotplug_path(libxl__gc *gc, libxl__device *dev)
+{
+    return GCSPRINTF("/local/domain/%u/libxl/hotplug/%u/%u",
+                     dev->backend_domid, dev->domid, dev->devid);
+}
+
 int libxl__device_generic_add(libxl__gc *gc, xs_transaction_t t,
         libxl__device *device, char **bents, char **fents)
 {
@@ -410,6 +416,7 @@ void libxl__prepare_ao_device(libxl__ao *ao, libxl__ao_device *aodev)
     aodev->rc = 0;
     aodev->dev = NULL;
     aodev->hotplug.num_exec = 0;
+    aodev->hotplug.version = 1;
     /* Initialize timer for QEMU Bodge and hotplug execution */
     libxl__ev_time_init(&aodev->timeout);
     aodev->active = 1;
@@ -974,7 +981,12 @@ static void device_hotplug_child_death_cb(libxl__egc *egc,
 
     device_hotplug_clean(gc, aodev);
 
-    if (status) {
+    if (status && aodev->action != LIBXL__DEVICE_ACTION_VERSION) {
+        /* If a hotplug script returns an error when called
+         * with the "version" argument it means it is using the old
+         * hotplug calling convention, and we don't have to print
+         * an error message.
+         */
         libxl_report_child_exitstatus(CTX, LIBXL__LOG_ERROR,
                                       aodev->what, pid, status);
         hotplug_error = libxl__xs_read(gc, XBT_NULL,
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index d69d819..e819bbd 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -1847,11 +1847,20 @@ typedef void libxl__device_callback(libxl__egc*, libxl__ao_device*);
  * Once _prepare has been called on a libxl__ao_device, it is safe to just
  * discard this struct, there's no need to call any destroy function.
  * _prepare can also be called multiple times with the same libxl__ao_device.
+ *
+ * If hotplug.version field is 2, the new hotplug script calling convention
+ * will be used to call the hotplug script. This new convention provides
+ * new actions to hotplug scripts, "prepare", "unprepare", "localattach",
+ * "localdetach" and "version". This new actions have been added to offload
+ * work done by hotplug scripts during the blackout phase of migration.
+ * "prepare" is called before the remote domain is paused, so as much
+ * operations as possible should be done in this phase.
  */
 _hidden void libxl__prepare_ao_device(libxl__ao *ao, libxl__ao_device *aodev);
 
 struct libxl__hotplug {
     int num_exec;
+    int version;
 };
 
 struct libxl__ao_device {
@@ -1861,6 +1870,8 @@ struct libxl__ao_device {
     libxl__device *dev;
     int force;
     libxl__device_callback *callback;
+    /* used by the VERISON and LOCALATTACH actions, set by caller */
+    libxl_device_disk *disk;
     /* return value, zeroed by user on entry, is valid on callback */
     int rc;
     /* private for multidev */
@@ -2044,6 +2055,17 @@ _hidden void libxl__initiate_device_remove(libxl__egc *egc,
                                            libxl__ao_device *aodev);
 
 /*
+ * libxl__device_xs_hotplug_path returns the xenstore hotplug
+ * path that is used to share information with the hotplug
+ * script.
+ *
+ * This path is only used by new hotplug scripts, that are
+ * specified using "method" instead of "script" in the disk
+ * parameters.
+ */
+_hidden char *libxl__device_xs_hotplug_path(libxl__gc *gc, libxl__device *dev);
+
+/*
  * libxl__get_hotplug_script_info returns the args and env that should
  * be passed to the hotplug script for the requested device.
  *
diff --git a/tools/libxl/libxl_linux.c b/tools/libxl/libxl_linux.c
index 531bc7e..00ffd6d 100644
--- a/tools/libxl/libxl_linux.c
+++ b/tools/libxl/libxl_linux.c
@@ -191,32 +191,63 @@ out:
 
 static int libxl__hotplug_disk(libxl__gc *gc, libxl__device *dev,
                                char ***args, char ***env,
-                               libxl__device_action action)
+                               libxl__device_action action,
+                               int hotplug_version)
 {
     char *be_path = libxl__device_backend_path(gc, dev);
+    char *hotplug_path = libxl__device_xs_hotplug_path(gc, dev);
     char *script;
     int nr = 0, rc = 0;
+    const int env_arraysize = 5;
+    const int arg_arraysize = 3;
 
-    script = libxl__xs_read(gc, XBT_NULL,
-                            GCSPRINTF("%s/%s", be_path, "script"));
-    if (!script) {
-        LOGEV(ERROR, errno, "unable to read script from %s", be_path);
-        rc = ERROR_FAIL;
-        goto error;
-    }
-
-    *env = get_hotplug_env(gc, script, dev);
-    if (!*env) {
+    switch (hotplug_version) {
+    case 1:
+        script = libxl__xs_read(gc, XBT_NULL, GCSPRINTF("%s/script", be_path));
+        if (!script) {
+            LOGEV(ERROR, errno, "unable to read script from %s", be_path);
+            rc = ERROR_FAIL;
+            goto error;
+        }
+        *env = get_hotplug_env(gc, script, dev);
+        if (!*env) {
+            rc = ERROR_FAIL;
+            goto error;
+        }
+        break;
+    case 2:
+        /* The new hotplug calling convention only uses two ENV variables:
+         * BACKEND_PATH: path to xenstore backend of the related device.
+         * HOTPLUG_PATH: path to the xenstore directory that can be used to
+         * pass extra parameters to the script.
+         */
+        script = libxl__xs_read(gc, XBT_NULL,
+                                GCSPRINTF("%s/script", hotplug_path));
+        if (!script) {
+            LOGEV(ERROR, errno, "unable to read script from %s", hotplug_path);
+            rc = ERROR_FAIL;
+            goto error;
+        }
+        GCNEW_ARRAY(*env, env_arraysize);
+        (*env)[nr++] = "BACKEND_PATH";
+        (*env)[nr++] = be_path;
+        (*env)[nr++] = "HOTPLUG_PATH";
+        (*env)[nr++] = hotplug_path;
+        (*env)[nr++] = NULL;
+        assert(nr == env_arraysize);
+        nr = 0;
+        break;
+    default:
+        LOG(ERROR, "unknown hotplug script version %d", hotplug_version);
         rc = ERROR_FAIL;
         goto error;
     }
 
-    const int arraysize = 3;
-    GCNEW_ARRAY(*args, arraysize);
+    GCNEW_ARRAY(*args, arg_arraysize);
     (*args)[nr++] = script;
     (*args)[nr++] = (char *) libxl__device_action_to_string(action);
     (*args)[nr++] = NULL;
-    assert(nr == arraysize);
+    assert(nr == arg_arraysize);
 
     rc = 1;
 
@@ -244,7 +275,7 @@ int libxl__get_hotplug_script_info(libxl__gc *gc, libxl__device *dev,
             rc = 0;
             goto out;
         }
-        rc = libxl__hotplug_disk(gc, dev, args, env, action);
+        rc = libxl__hotplug_disk(gc, dev, args, env, action, hotplug->version);
         break;
     case LIBXL__DEVICE_KIND_VIF:
         /*
diff --git a/tools/libxl/libxl_types_internal.idl b/tools/libxl/libxl_types_internal.idl
index cb9444f..253bb18 100644
--- a/tools/libxl/libxl_types_internal.idl
+++ b/tools/libxl/libxl_types_internal.idl
@@ -37,4 +37,9 @@ libxl__device_console = Struct("device_console", [
 libxl__device_action = Enumeration("device_action", [
     (1, "ADD"),
     (2, "REMOVE"),
+    (3, "PREPARE"),
+    (4, "UNPREPARE"),
+    (5, "LOCALATTACH"),
+    (6, "LOCALDETACH"),
+    (7, "VERSION"),
     ])
-- 
1.7.7.5 (Apple Git-26)


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