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-common.h"
  29 #include "qemu/atomic.h"
  30 #include "exec/cpu-common.h"
  31 #include "sysemu/kvm.h"
  32 #include "sysemu/balloon.h"
  33 #include "trace-root.h"
  34 #include "qapi/error.h"
  35 #include "qapi/qapi-commands-misc.h"
  36 #include "qapi/qmp/qerror.h"
  37
  38 static QEMUBalloonEvent *balloon_event_fn;
  39 static QEMUBalloonStatus *balloon_stat_fn;
  40 static void *balloon_opaque;
  41 static int balloon_inhibit_count;
  42
  43 bool qemu_balloon_is_inhibited(void)
  44 {
  45     return atomic_read(&balloon_inhibit_count) > 0;
  46 }
  47
  48 void qemu_balloon_inhibit(bool state)
  49 {
  50     if (state) {
  51         atomic_inc(&balloon_inhibit_count);
  52     } else {
  53         atomic_dec(&balloon_inhibit_count);
  54     }
  55
  56     assert(atomic_read(&balloon_inhibit_count) >= 0);
  57 }
  58
  59 static bool have_balloon(Error **errp)
  60 {
  61     if (kvm_enabled() && !kvm_has_sync_mmu()) {
  62         error_set(errp, ERROR_CLASS_KVM_MISSING_CAP,
  63                   "Using KVM without synchronous MMU, balloon unavailable");
  64         return false;
  65     }
  66     if (!balloon_event_fn) {
  67         error_set(errp, ERROR_CLASS_DEVICE_NOT_ACTIVE,
  68                   "No balloon device has been activated");
  69         return false;
  70     }
  71     return true;
  72 }
  73
  74 int qemu_add_balloon_handler(QEMUBalloonEvent *event_func,
  75                              QEMUBalloonStatus *stat_func, void *opaque)
  76 {
  77     if (balloon_event_fn || balloon_stat_fn || balloon_opaque) {
  78         /* We're already registered one balloon handler.  How many can
  79          * a guest really have?
  80          */
  81         return -1;
  82     }
  83     balloon_event_fn = event_func;
  84     balloon_stat_fn = stat_func;
  85     balloon_opaque = opaque;
  86     return 0;
  87 }
  88
  89 void qemu_remove_balloon_handler(void *opaque)
  90 {
  91     if (balloon_opaque != opaque) {
  92         return;
  93     }
  94     balloon_event_fn = NULL;
  95     balloon_stat_fn = NULL;
  96     balloon_opaque = NULL;
  97 }
  98
  99 BalloonInfo *qmp_query_balloon(Error **errp)
 100 {
 101     BalloonInfo *info;
 102
 103     if (!have_balloon(errp)) {
 104         return NULL;
 105     }
 106
 107     info = g_malloc0(sizeof(*info));
 108     balloon_stat_fn(balloon_opaque, info);
 109     return info;
 110 }
 111
 112 void qmp_balloon(int64_t target, Error **errp)
 113 {
 114     if (!have_balloon(errp)) {
 115         return;
 116     }
 117
 118     if (target <= 0) {
 119         error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "target", "a size");
 120         return;
 121     }
 122
 123     trace_balloon_event(balloon_opaque, target);
 124     balloon_event_fn(balloon_opaque, target);
 125 }