libxl: change ao_device_remove to ao_device

Introduce a new structure to track state of device backends, that will
be used in following patches on this series.

This structure if used for both device creation and device
destruction and removes libxl__ao_device_remove.

Signed-off-by: Roger Pau Monne <roger.pau@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Committed-by: Ian Campbell <ian.campbell@citrix.com>

1 files changed, 136 insertions, 7 deletions

diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 2781398be4..5d985ff9aa 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -74,6 +74,7 @@
 
 #define LIBXL_DESTROY_TIMEOUT 10
 #define LIBXL_DEVICE_MODEL_START_TIMEOUT 10
+#define LIBXL_QEMU_BODGE_TIMEOUT 2
 #define LIBXL_XENCONSOLE_LIMIT 1048576
 #define LIBXL_XENCONSOLE_PROTOCOL "vt100"
 #define LIBXL_MAXMEM_CONSTANT 1024
@@ -350,6 +351,12 @@ typedef struct {
     libxl__device_kind kind;
 } libxl__device;
 
+/* Used to know if backend of given device is QEMU */
+#define QEMU_BACKEND(dev) (\
+    (dev)->backend_kind == LIBXL__DEVICE_KIND_QDISK || \
+    (dev)->backend_kind == LIBXL__DEVICE_KIND_VFB || \
+    (dev)->backend_kind == LIBXL__DEVICE_KIND_VKBD)
+
 #define XC_PCI_BDF             "0x%x, 0x%x, 0x%x, 0x%x"
 #define PCI_DEVFN(slot, func)   ((((slot) & 0x1f) << 3) | ((func) & 0x07))
 #define PCI_SLOT(devfn)         (((devfn) >> 3) & 0x1f)
@@ -899,13 +906,6 @@ _hidden const char *libxl__device_nic_devname(libxl__gc *gc,
                                               uint32_t devid,
                                               libxl_nic_type type);
 
-/* Arranges that dev will be removed from its guest.  When
- * this is done, the ao will be completed.  An error
- * return from libxl__initiate_device_remove means that the ao
- * will _not_ be completed and the caller must do so. */
-_hidden int libxl__initiate_device_remove(libxl__egc*, libxl__ao*,
-                                          libxl__device *dev);
-
 /*
  * libxl__ev_devstate - waits a given time for a device to
  * reach a given state.  Follows the libxl_ev_* conventions.
@@ -2007,6 +2007,135 @@ _hidden void libxl__bootloader_init(libxl__bootloader_state *bl);
  * If callback is passed rc==0, will have updated st->info appropriately */
 _hidden void libxl__bootloader_run(libxl__egc*, libxl__bootloader_state *st);
 
+/*----- device addition/removal -----*/
+
+/* Action to perform (either connect or disconnect) */
+typedef enum {
+    DEVICE_CONNECT,
+    DEVICE_DISCONNECT
+} libxl__device_action;
+
+typedef struct libxl__ao_device libxl__ao_device;
+typedef void libxl__device_callback(libxl__egc*, libxl__ao_device*);
+
+/* This functions sets the necessary libxl__ao_device struct values to use
+ * safely inside functions. It marks the operation as "active"
+ * since we need to be sure that all device status structs are set
+ * to active before start queueing events, or we might call
+ * ao_complete before all devices had finished
+ *
+ * libxl__initiate_device_{remove/addition} should not be called without
+ * calling libxl__prepare_ao_device first, since it initializes the private
+ * fields of the struct libxl__ao_device to what this functions expect.
+ *
+ * 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.
+ */
+_hidden void libxl__prepare_ao_device(libxl__ao *ao, libxl__ao_device *aodev);
+
+struct libxl__ao_device {
+    /* filled in by user */
+    libxl__ao *ao;
+    libxl__device_action action;
+    libxl__device *dev;
+    int force;
+    libxl__device_callback *callback;
+    /* private for implementation */
+    int rc;
+    libxl__ev_devstate backend_ds;
+    /* Bodge for Qemu devices */
+    libxl__ev_time timeout;
+};
+
+/*
+ * Algorithm for handling device removal (including domain
+ * destruction).  This is somewhat subtle because we may already have
+ * killed the domain and caused the death of qemu.
+ *
+ * In current versions of qemu there is no mechanism for ensuring that
+ * the resources used by its devices (both emulated and any PV devices
+ * provided by qemu) are freed (eg, fds closed) before it shuts down,
+ * and no confirmation from a terminating qemu back to the toolstack.
+ *
+ * This will need to be fixed in Xen 4.3.  In the meantime (Xen 4.2)
+ * we implement a bodge.
+ *
+ *      WE WANT TO UNPLUG         WE WANT TO SHUT DOWN OR DESTROY
+ *                    |                           |
+ *                    |             LIBXL SENDS SIGHUP TO QEMU
+ *                    |      .....................|........................
+ *                    |      : XEN 4.3+ PLANNED   |                       :
+ *                    |      :      QEMU TEARS DOWN ALL DEVICES           :
+ *                    |      :      FREES RESOURCES (closing fds)         :
+ *                    |      :      SETS PV BACKENDS TO STATE 5,          :
+ *                    |      :       waits for PV frontends to shut down  :
+ *                    |      :       SETS PV BACKENDS TO STATE 6          :
+ *                    |      :                    |                       :
+ *                    |      :      QEMU NOTIFIES TOOLSTACK (via          :
+ *                    |      :       xenstore) that it is exiting         :
+ *                    |      :      QEMU EXITS (parent may be init)       :
+ *                    |      :                    |                       :
+ *                    |      :        TOOLSTACK WAITS FOR QEMU            :
+ *                    |      :        notices qemu has finished           :
+ *                    |      :....................|.......................:
+ *                    |      .--------------------'
+ *                    V      V
+ *                  for each device
+ *                 we want to unplug/remove
+ *       ..................|...........................................
+ *       :                 V                       XEN 4.2 RACY BODGE :
+ *       :      device is provided by    qemu                         :
+ *       :            |            `-----------.                      :
+ *       :   something|                        V                      :
+ *       :    else, eg|             domain (that is domain for which  :
+ *       :     blkback|              this PV device is the backend,   :
+ *       :            |              which might be the stub dm)      :
+ *       :            |                is still alive?                :
+ *       :            |                  |        |                   :
+ *       :            |                  |alive   |dead               :
+ *       :            |<-----------------'        |                   :
+ *       :            |    hopefully qemu is      |                   :
+ *       :            |       still running       |                   :
+ *       :............|.................          |                   :
+ *             ,----->|                :     we may be racing         :
+ *             |    backend state?     :      with qemu's death       :
+ *             ^      |         |      :          |                   :
+ *     xenstore|      |other    |6     :      WAIT 2.0s               :
+ *     conflict|      |         |      :       TIMEOUT                :
+ *             |   WRITE B.E.   |      :          |                   :
+ *             |    STATE:=5    |      :     hopefully qemu has       :
+ *             `---'  |         |      :      gone by now and         :
+ *                    |ok       |      :      freed its resources     :
+ *                    |         |      :          |                   :
+ *              WAIT FOR        |      :     SET B.E.                 :
+ *              STATE==6        |      :      STATE:=6                :
+ *              /     |         |      :..........|...................:
+ *      timeout/    ok|         |                 |
+ *            /       |         |                 |
+ *           |    RUN HOTPLUG <-'<----------------'
+ *           |      SCRIPT
+ *           |        |
+ *           `---> NUKE
+ *                  BACKEND
+ *                    |
+ *                   DONE.
+ */
+
+/* Arranges that dev will be removed to the guest, and the
+ * hotplug scripts will be executed (if necessary). When
+ * this is done (or an error happens), the callback in
+ * aodev->callback will be called.
+ *
+ * The libxl__ao_device passed to this function should be
+ * prepared using libxl__prepare_ao_device prior to calling
+ * this function.
+ *
+ * Once finished, aodev->callback will be executed.
+ */
+_hidden void libxl__initiate_device_remove(libxl__egc *egc,
+                                           libxl__ao_device *aodev);
+
 /*----- Domain creation -----*/
 
 typedef struct libxl__domain_create_state libxl__domain_create_state;