balloon.c

   1 /*
   2  * Generic Balloon handlers and management
   3  *
   4  * Copyright (c) 2003-2008 Fabrice Bellard
   5  * Copyright (C) 2011 Red Hat, Inc.
   6  * Copyright (C) 2011 Amit Shah <amit.shah@redhat.com>
   7  *
   8  * Permission is hereby granted, free of charge, to any person obtaining a copy
   9  * of this software and associated documentation files (the "Software"), to deal
  10  * in the Software without restriction, including without limitation the rights
  11  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  12  * copies of the Software, and to permit persons to whom the Software is
  13  * furnished to do so, subject to the following conditions:
  14  *
  15  * The above copyright notice and this permission notice shall be included in
  16  * all copies or substantial portions of the Software.
  17  *
  18  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  19  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  20  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  21  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  22  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  23  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  24  * THE SOFTWARE.
  25  */
  26
  27 #include "qemu/osdep.h"
  28 #include "qemu/atomic.h"
  29 #include "sysemu/kvm.h"
  30 #include "sysemu/balloon.h"
  31 #include "trace-root.h"
  32 #include "qapi/error.h"
  33 #include "qapi/qapi-commands-misc.h"
  34 #include "qapi/qmp/qerror.h"
  35
  36 static QEMUBalloonEvent *balloon_event_fn;
  37 static QEMUBalloonStatus *balloon_stat_fn;
  38 static void *balloon_opaque;
  39 static int balloon_inhibit_count;
  40
  41 bool qemu_balloon_is_inhibited(void)
  42 {
  43     return atomic_read(&balloon_inhibit_count) > 0;
  44 }
  45
  46 void qemu_balloon_inhibit(bool state)
  47 {
  48     if (state) {
  49         atomic_inc(&balloon_inhibit_count);
  50     } else {
  51         atomic_dec(&balloon_inhibit_count);
  52     }
  53
  54     assert(atomic_read(&balloon_inhibit_count) >= 0);
  55 }
  56
  57 static bool have_balloon(Error **errp)
  58 {
  59     if (kvm_enabled() && !kvm_has_sync_mmu()) {
  60         error_set(errp, ERROR_CLASS_KVM_MISSING_CAP,
  61                   "Using KVM without synchronous MMU, balloon unavailable");
  62         return false;
  63     }
  64     if (!balloon_event_fn) {
  65         error_set(errp, ERROR_CLASS_DEVICE_NOT_ACTIVE,
  66                   "No balloon device has been activated");
  67         return false;
  68     }
  69     return true;
  70 }
  71
  72 int qemu_add_balloon_handler(QEMUBalloonEvent *event_func,
  73                              QEMUBalloonStatus *stat_func, void *opaque)
  74 {
  75     if (balloon_event_fn || balloon_stat_fn || balloon_opaque) {
  76         /* We're already registered one balloon handler.  How many can
  77          * a guest really have?
  78          */
  79         return -1;
  80     }
  81     balloon_event_fn = event_func;
  82     balloon_stat_fn = stat_func;
  83     balloon_opaque = opaque;
  84     return 0;
  85 }
  86
  87 void qemu_remove_balloon_handler(void *opaque)
  88 {
  89     if (balloon_opaque != opaque) {
  90         return;
  91     }
  92     balloon_event_fn = NULL;
  93     balloon_stat_fn = NULL;
  94     balloon_opaque = NULL;
  95 }
  96
  97 BalloonInfo *qmp_query_balloon(Error **errp)
  98 {
  99     BalloonInfo *info;
 100
 101     if (!have_balloon(errp)) {
 102         return NULL;
 103     }
 104
 105     info = g_malloc0(sizeof(*info));
 106     balloon_stat_fn(balloon_opaque, info);
 107     return info;
 108 }
 109
 110 void qmp_balloon(int64_t target, Error **errp)
 111 {
 112     if (!have_balloon(errp)) {
 113         return;
 114     }
 115
 116     if (target <= 0) {
 117         error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "target", "a size");
 118         return;
 119     }
 120
 121     trace_balloon_event(balloon_opaque, target);
 122     balloon_event_fn(balloon_opaque, target);
 123 }