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 "exec/cpu-common.h"
  30 #include "sysemu/kvm.h"
  31 #include "sysemu/balloon.h"
  32 #include "trace-root.h"
  33 #include "qapi/error.h"
  34 #include "qapi/qapi-commands-misc.h"
  35 #include "qapi/qmp/qerror.h"
  36
  37 static QEMUBalloonEvent *balloon_event_fn;
  38 static QEMUBalloonStatus *balloon_stat_fn;
  39 static void *balloon_opaque;
  40 static int balloon_inhibit_count;
  41
  42 bool qemu_balloon_is_inhibited(void)
  43 {
  44     return atomic_read(&balloon_inhibit_count) > 0;
  45 }
  46
  47 void qemu_balloon_inhibit(bool state)
  48 {
  49     if (state) {
  50         atomic_inc(&balloon_inhibit_count);
  51     } else {
  52         atomic_dec(&balloon_inhibit_count);
  53     }
  54
  55     assert(atomic_read(&balloon_inhibit_count) >= 0);
  56 }
  57
  58 static bool have_balloon(Error **errp)
  59 {
  60     if (kvm_enabled() && !kvm_has_sync_mmu()) {
  61         error_set(errp, ERROR_CLASS_KVM_MISSING_CAP,
  62                   "Using KVM without synchronous MMU, balloon unavailable");
  63         return false;
  64     }
  65     if (!balloon_event_fn) {
  66         error_set(errp, ERROR_CLASS_DEVICE_NOT_ACTIVE,
  67                   "No balloon device has been activated");
  68         return false;
  69     }
  70     return true;
  71 }
  72
  73 int qemu_add_balloon_handler(QEMUBalloonEvent *event_func,
  74                              QEMUBalloonStatus *stat_func, void *opaque)
  75 {
  76     if (balloon_event_fn || balloon_stat_fn || balloon_opaque) {
  77         /* We're already registered one balloon handler.  How many can
  78          * a guest really have?
  79          */
  80         return -1;
  81     }
  82     balloon_event_fn = event_func;
  83     balloon_stat_fn = stat_func;
  84     balloon_opaque = opaque;
  85     return 0;
  86 }
  87
  88 void qemu_remove_balloon_handler(void *opaque)
  89 {
  90     if (balloon_opaque != opaque) {
  91         return;
  92     }
  93     balloon_event_fn = NULL;
  94     balloon_stat_fn = NULL;
  95     balloon_opaque = NULL;
  96 }
  97
  98 BalloonInfo *qmp_query_balloon(Error **errp)
  99 {
 100     BalloonInfo *info;
 101
 102     if (!have_balloon(errp)) {
 103         return NULL;
 104     }
 105
 106     info = g_malloc0(sizeof(*info));
 107     balloon_stat_fn(balloon_opaque, info);
 108     return info;
 109 }
 110
 111 void qmp_balloon(int64_t target, Error **errp)
 112 {
 113     if (!have_balloon(errp)) {
 114         return;
 115     }
 116
 117     if (target <= 0) {
 118         error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "target", "a size");
 119         return;
 120     }
 121
 122     trace_balloon_event(balloon_opaque, target);
 123     balloon_event_fn(balloon_opaque, target);
 124 }