[PATCH v6 08/13] libxl: add option to choose who executes hotplug scripts

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

Add and option to xl.conf file to decide if hotplug scripts are
executed from the toolstack (xl) or from udev as it used to be in the
past.

This option is only introduced in this patch, but it has no effect
since the code to call hotplug scripts from libxl is introduced in a
latter patch.

This choice will be saved in "libxl/disable_udev", as specified in the
DISABLE_UDEV_PATH constant.

Changes since v2:

 * Change atoi(...) to !!atoi(...) to prevent returning negative
   values from xenstore (which will be handled as errors).

 * Check for errors on the return value of libxl__hotplug_settings.

Changes since v1:

 * Used an auxiliary function to check for the current setting.

Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Signed-off-by: Roger Pau Monne <roger.pau@citrix.com>
---
 docs/man/xl.conf.pod.5       |    8 ++++++++
 tools/examples/xl.conf       |    5 +++++
 tools/libxl/libxl_create.c   |   36 +++++++++++++++++++++++++++++++++++-
 tools/libxl/libxl_internal.c |   19 +++++++++++++++++++
 tools/libxl/libxl_internal.h |    3 +++
 tools/libxl/libxl_types.idl  |    1 +
 tools/libxl/xl.c             |    4 ++++
 tools/libxl/xl.h             |    1 +
 tools/libxl/xl_cmdimpl.c     |    1 +
 9 files changed, 77 insertions(+), 1 deletions(-)

diff --git a/docs/man/xl.conf.pod.5 b/docs/man/xl.conf.pod.5
index 149430c..23932be 100644
--- a/docs/man/xl.conf.pod.5
+++ b/docs/man/xl.conf.pod.5
@@ -55,6 +55,14 @@ default.
 
 Default: C<1>
 
+=item B<run_hotplug_scripts=BOOLEAN>
+
+If disabled hotplug scripts will be called from udev, as it used to
+be in the previous releases. With the default option, hotplug scripts
+will be launched by xl directly.
+
+Default: C<1>
+
 =item B<lockfile="PATH">
 
 Sets the path to the lock file used by xl to serialise certain
diff --git a/tools/examples/xl.conf b/tools/examples/xl.conf
index ebf057c..28ab796 100644
--- a/tools/examples/xl.conf
+++ b/tools/examples/xl.conf
@@ -15,3 +15,8 @@
 
 # first block device to be used for temporary VM disk mounts
 #blkdev_start="xvda"
+
+# default option to run hotplug scripts from xl
+# if disabled the old behaviour will be used, and hotplug scripts will be
+# launched by udev.
+#run_hotplug_scripts=1
diff --git a/tools/libxl/libxl_create.c b/tools/libxl/libxl_create.c
index 274f5d4..d47d1ea 100644
--- a/tools/libxl/libxl_create.c
+++ b/tools/libxl/libxl_create.c
@@ -404,7 +404,7 @@ int libxl__domain_make(libxl__gc *gc, libxl_domain_create_info *info,
                        uint32_t *domid)
 {
     libxl_ctx *ctx = libxl__gc_owner(gc);
-    int flags, ret, rc;
+    int flags, ret, rc, nb_vm;
     char *uuid_string;
     char *dom_path, *vm_path, *libxl_path;
     struct xs_permissions roperm[2];
@@ -525,6 +525,40 @@ retry_transaction:
             libxl__sprintf(gc, "%s/hvmloader/generation-id-address", dom_path),
                         rwperm, ARRAY_SIZE(rwperm));
 
+    if (libxl_list_vm(ctx, &nb_vm) < 0) {
+        LOG(ERROR, "cannot get number of running guests");
+        rc = ERROR_FAIL;
+        goto out;
+    }
+
+    int hotplug_setting = libxl__hotplug_settings(gc, t);
+    if (hotplug_setting < 0) {
+        LOG(ERROR, "unable to get current hotplug scripts execution setting");
+        rc = ERROR_FAIL;
+        goto out;
+    }
+    if (libxl_defbool_val(info->run_hotplug_scripts) != hotplug_setting &&
+        (nb_vm - 1)) {
+        LOG(ERROR, "cannot change hotplug execution option once set, "
+                    "please shutdown all guests before changing it");
+        rc = ERROR_FAIL;
+        goto out;
+    }
+
+    if (libxl_defbool_val(info->run_hotplug_scripts)) {
+        rc = libxl__xs_write(gc, t, DISABLE_UDEV_PATH, "1");
+        if (rc) {
+            LOGE(ERROR, "unable to write %s = 1", DISABLE_UDEV_PATH);
+            goto out;
+        }
+    } else {
+        rc = xs_rm(ctx->xsh, t, DISABLE_UDEV_PATH);
+        if (rc) {
+            LOGE(ERROR, "unable to delete %s", DISABLE_UDEV_PATH);
+            goto out;
+        }
+    }
+
     xs_write(ctx->xsh, t, libxl__sprintf(gc, "%s/uuid", vm_path), uuid_string, strlen(uuid_string));
     xs_write(ctx->xsh, t, libxl__sprintf(gc, "%s/name", vm_path), info->name, strlen(info->name));
 
diff --git a/tools/libxl/libxl_internal.c b/tools/libxl/libxl_internal.c
index 8139520..bc56f21 100644
--- a/tools/libxl/libxl_internal.c
+++ b/tools/libxl/libxl_internal.c
@@ -346,6 +346,25 @@ libxl_device_model_version libxl__device_model_version_running(libxl__gc *gc,
     return value;
 }
 
+int libxl__hotplug_settings(libxl__gc *gc, xs_transaction_t t)
+{
+    int rc = 0;
+    char *val;
+
+    val = libxl__xs_read(gc, t, DISABLE_UDEV_PATH);
+    if (!val && errno != ENOENT) {
+        LOGE(ERROR, "cannot read %s from xenstore", DISABLE_UDEV_PATH);
+        rc = ERROR_FAIL;
+        goto out;
+    }
+    if (!val) val = "0";
+
+    rc = !!atoi(val);
+
+out:
+    return rc;
+}
+
 /*
  * Local variables:
  * mode: C
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 1d4726b..1350ba9 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -88,6 +88,7 @@
 #define STUBDOM_CONSOLE_SERIAL 3
 #define STUBDOM_SPECIAL_CONSOLES 3
 #define TAP_DEVICE_SUFFIX "-emu"
+#define DISABLE_UDEV_PATH "libxl/disable_udev"
 
 #define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
 
@@ -1415,6 +1416,8 @@ _hidden libxl__json_object *libxl__json_parse(libxl__gc *gc, const char *s);
 _hidden libxl_device_model_version
 libxl__device_model_version_running(libxl__gc *gc, uint32_t domid);
 
+/* Check how executes hotplug script currently */
+int libxl__hotplug_settings(libxl__gc *gc, xs_transaction_t t);
 
 /*
  * Calling context and GC for event-generating functions:
diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
index b727abb..1ede19e 100644
--- a/tools/libxl/libxl_types.idl
+++ b/tools/libxl/libxl_types.idl
@@ -221,6 +221,7 @@ libxl_domain_create_info = Struct("domain_create_info",[
     ("xsdata",       libxl_key_value_list),
     ("platformdata", libxl_key_value_list),
     ("poolid",       uint32),
+    ("run_hotplug_scripts",libxl_defbool),
     ], dir=DIR_IN)
 
 MemKB = UInt(64, init_val = "LIBXL_MEMKB_DEFAULT")
diff --git a/tools/libxl/xl.c b/tools/libxl/xl.c
index a5ada03..460a6df 100644
--- a/tools/libxl/xl.c
+++ b/tools/libxl/xl.c
@@ -39,6 +39,7 @@ int dryrun_only;
 int force_execution;
 int autoballoon = 1;
 char *blkdev_start;
+libxl_defbool run_hotplug_scripts;
 char *lockfile;
 char *default_vifscript = NULL;
 char *default_bridge = NULL;
@@ -70,6 +71,9 @@ static void parse_global_config(const char *configfile,
     if (!xlu_cfg_get_long (config, "autoballoon", &l, 0))
         autoballoon = l;
 
+    libxl_defbool_setdefault(&run_hotplug_scripts, true);
+    xlu_cfg_get_defbool(config, "run_hotplug_scripts", &run_hotplug_scripts, 0);
+
     if (!xlu_cfg_get_string (config, "lockfile", &buf, 0))
         lockfile = strdup(buf);
     else {
diff --git a/tools/libxl/xl.h b/tools/libxl/xl.h
index 59556b5..fddaecb 100644
--- a/tools/libxl/xl.h
+++ b/tools/libxl/xl.h
@@ -140,6 +140,7 @@ int xl_child_pid(xlchildnum); /* returns 0 if child struct is not in use */
 
 /* global options */
 extern int autoballoon;
+extern libxl_defbool run_hotplug_scripts;
 extern int dryrun_only;
 extern char *lockfile;
 extern char *default_vifscript;
diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c
index 404c9c2..fd980b1 100644
--- a/tools/libxl/xl_cmdimpl.c
+++ b/tools/libxl/xl_cmdimpl.c
@@ -594,6 +594,7 @@ static void parse_config_data(const char *config_source,
         }
     }
 
+    c_info->run_hotplug_scripts = run_hotplug_scripts;
     c_info->type = LIBXL_DOMAIN_TYPE_PV;
     if (!xlu_cfg_get_string (config, "builder", &buf, 0) &&
         !strncmp(buf, "hvm", strlen(buf)))
-- 
1.7.7.5 (Apple Git-26)