libxl: introduce libxl__qmp_query_cpus

It interrogates QEMU for CPUs and update the bitmap accordingly.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Dario Faggioli <dario.faggioli@citrix.com>
Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>

tools/libxl/libxl_internal.h

@@ -1794,6 +1794,9 @@ _hidden int libxl__qmp_set_global_dirty_log(libxl__gc *gc, int domid, bool enabl
 _hidden int libxl__qmp_insert_cdrom(libxl__gc *gc, int domid, const libxl_device_disk *disk);
 /* Add a virtual CPU */
 _hidden int libxl__qmp_cpu_add(libxl__gc *gc, int domid, int index);
+/* Query the bitmap of CPUs */
+_hidden int libxl__qmp_query_cpus(libxl__gc *gc, int domid,
+                                  libxl_bitmap *map);
 /* Start NBD server */
 _hidden int libxl__qmp_nbd_server_start(libxl__gc *gc, int domid,
                                         const char *host, const char *port);

tools/libxl/libxl_qmp.c

@@ -979,6 +979,44 @@ int libxl__qmp_cpu_add(libxl__gc *gc, int domid, int idx)
     return qmp_run_command(gc, domid, "cpu-add", args, NULL, NULL);
 }
 
+static int query_cpus_callback(libxl__qmp_handler *qmp,
+                               const libxl__json_object *response,
+                               void *opaque)
+{
+    libxl_bitmap *map = opaque;
+    unsigned int i;
+    const libxl__json_object *cpu = NULL;
+    int rc;
+    GC_INIT(qmp->ctx);
+
+    libxl_bitmap_set_none(map);
+    for (i = 0; (cpu = libxl__json_array_get(response, i)); i++) {
+        unsigned int idx;
+        const libxl__json_object *o;
+
+        o = libxl__json_map_get("CPU", cpu, JSON_INTEGER);
+        if (!o) {
+            LOG(ERROR, "Failed to retrieve CPU index.");
+            rc = ERROR_FAIL;
+            goto out;
+        }
+
+        idx = libxl__json_object_get_integer(o);
+        libxl_bitmap_set(map, idx);
+    }
+
+    rc = 0;
+out:
+    GC_FREE;
+    return rc;
+}
+
+int libxl__qmp_query_cpus(libxl__gc *gc, int domid, libxl_bitmap *map)
+{
+    return qmp_run_command(gc, domid, "query-cpus", NULL,
+                           query_cpus_callback, map);
+}
+
 int libxl__qmp_nbd_server_start(libxl__gc *gc, int domid,
                                 const char *host, const char *port)
 {