[Xen-devel] [PATCH v6 08/11] libxl: QEMU startup sync based on QMP

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

This is only activated when dm_restrict=1, as explained in the previous
patch "libxl_dm: Pre-open QMP socket for QEMU"

Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---

Notes:
    v6:
        invent ERROR_QEMU_API
        return better rc: ERROR_QEMU_API or ERROR_NOT_READY
        enhance log messages (debug and error)
    
    v5:
        removed empty success branch in device_model_qmp_cb()
        call libxl__ev_qmp_init() earlier in libxl__spawn_local_dm.
            otherwise the error path would use an uninitialised
            libxl__ev_qmp.
    
    v4:
        moved to libxl__dm_spawn_* from libxl__spawn_*

 tools/libxl/libxl_dm.c       | 55 ++++++++++++++++++++++++++++++++++++
 tools/libxl/libxl_internal.h |  1 +
 tools/libxl/libxl_types.idl  |  1 +
 3 files changed, 57 insertions(+)

diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
index 3bf1e37894..2417abe651 100644
--- a/tools/libxl/libxl_dm.c
+++ b/tools/libxl/libxl_dm.c
@@ -2313,6 +2313,9 @@ static void device_model_startup_failed(libxl__egc *egc,
                                         int rc);
 static void device_model_detached(libxl__egc *egc,
                                   libxl__spawn_state *spawn);
+static void device_model_qmp_cb(libxl__egc *egc, libxl__ev_qmp *ev,
+                                const libxl__json_object *response,
+                                int rc);
 
 /* our "next step" function, called from those callbacks and elsewhere */
 static void device_model_spawn_outcome(libxl__egc *egc,
@@ -2343,6 +2346,8 @@ void libxl__spawn_local_dm(libxl__egc *egc, 
libxl__dm_spawn_state *dmss)
     const char *dm;
     int dm_state_fd = -1;
 
+    libxl__ev_qmp_init(&dmss->qmp);
+
     if (libxl_defbool_val(b_info->device_model_stubdomain)) {
         abort();
     }
@@ -2450,6 +2455,16 @@ retry_transaction:
     spawn->failure_cb = device_model_startup_failed;
     spawn->detached_cb = device_model_detached;
 
+    if (state->dm_monitor_fd >= 0) {
+        /* There is a valid QMP socket available now,
+         * use it to find out when QEMU is ready */
+        dmss->qmp.callback = device_model_qmp_cb;
+        dmss->qmp.domid = domid;
+        dmss->qmp.fd = -1;
+        rc = libxl__ev_qmp_send(gc, &dmss->qmp, "query-status", NULL);
+        if (rc) goto out_close;
+    }
+
     rc = libxl__spawn_spawn(egc, spawn);
     if (rc < 0)
         goto out_close;
@@ -2524,6 +2539,44 @@ static void device_model_detached(libxl__egc *egc,
     device_model_spawn_outcome(egc, dmss, 0);
 }
 
+static void device_model_qmp_cb(libxl__egc *egc, libxl__ev_qmp *ev,
+                                const libxl__json_object *response,
+                                int rc)
+{
+    EGC_GC;
+    libxl__dm_spawn_state *dmss = CONTAINER_OF(ev, *dmss, qmp);
+    const libxl__json_object *o;
+    const char *status;
+
+    libxl__ev_qmp_dispose(gc, ev);
+
+    if (rc)
+        goto failed;
+
+    o = libxl__json_map_get("status", response, JSON_STRING);
+    if (!o) {
+        LOGD(ERROR, ev->domid,
+             "Missing \"status\" in response to \"query-status\"");
+        LOGD(DEBUG, ev->domid, ".. instead, got: %s",
+             libxl__json_object_to_json(gc, response));
+        rc = ERROR_QEMU_API;
+        goto failed;
+    }
+    status = libxl__json_object_get_string(o);
+    if (strcmp(status, "running")) {
+        LOGD(ERROR, ev->domid, "Unexpected QEMU status: %s", status);
+        rc = ERROR_NOT_READY;
+        goto failed;
+    }
+
+    libxl__spawn_initiate_detach(gc, &dmss->spawn);
+    return;
+
+failed:
+    LOGD(ERROR, ev->domid, "QEMU did not start properly, rc=%d", rc);
+    libxl__spawn_initiate_failure(gc, &dmss->spawn, rc);
+}
+
 static void device_model_spawn_outcome(libxl__egc *egc,
                                        libxl__dm_spawn_state *dmss,
                                        int rc)
@@ -2547,6 +2600,8 @@ static void device_model_spawn_outcome(libxl__egc *egc,
         }
     }
 
+    libxl__ev_qmp_dispose(gc, &dmss->qmp);
+
  out:
     dmss->callback(egc, dmss, rc);
 }
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index b768d1b09f..de3862c839 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -3898,6 +3898,7 @@ struct libxl__dm_spawn_state {
     libxl_domain_config *guest_config;
     libxl__domain_build_state *build_state; /* relates to guest_domid */
     libxl__dm_spawn_cb *callback;
+    libxl__ev_qmp qmp;
 };
 
 _hidden void libxl__spawn_local_dm(libxl__egc *egc, libxl__dm_spawn_state*);
diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
index fec42b260c..a0912718e0 100644
--- a/tools/libxl/libxl_types.idl
+++ b/tools/libxl/libxl_types.idl
@@ -75,6 +75,7 @@ libxl_error = Enumeration("error", [
     (-29, "QMP_COMMAND_NOT_FOUND"), # the requested command has not been found
     (-30, "QMP_DEVICE_NOT_ACTIVE"), # a device has failed to be become active
     (-31, "QMP_DEVICE_NOT_FOUND"), # the requested device has not been found
+    (-32, "QEMU_API"),
     ], value_namespace = "")
 
 libxl_domain_type = Enumeration("domain_type", [
-- 
Anthony PERARD


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