371ff5a3f0
Postcopy detects accesses to pages that haven't been transferred yet using userfaultfd, and it causes exceptions on pages that are 'not present'. Ballooning also causes pages to be marked as 'not present' when the guest inflates the balloon. Potentially a balloon could be inflated to discard pages that are currently inflight during postcopy and that may be arriving at about the same time. To avoid this confusion, disable ballooning during postcopy. When disabled we drop balloon requests from the guest. Since ballooning is generally initiated by the host, the management system should avoid initiating any balloon instructions to the guest during migration, although it's not possible to know how long it would take a guest to process a request made prior to the start of migration. Guest initiated ballooning will not know if it's really freed a page of host memory or not. Queueing the requests until after migration would be nice, but is non-trivial, since the set of inflate/deflate requests have to be compared with the state of the page to know what the final outcome is allowed to be. Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com> Reviewed-by: Juan Quintela <quintela@redhat.com> Reviewed-by: Amit Shah <amit.shah@redhat.com> Signed-off-by: Juan Quintela <quintela@redhat.com>
118 lines
3.3 KiB
C
118 lines
3.3 KiB
C
/*
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* Generic Balloon handlers and management
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*
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* Copyright (c) 2003-2008 Fabrice Bellard
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* Copyright (C) 2011 Red Hat, Inc.
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* Copyright (C) 2011 Amit Shah <amit.shah@redhat.com>
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#include "qemu-common.h"
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#include "exec/cpu-common.h"
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#include "sysemu/kvm.h"
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#include "sysemu/balloon.h"
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#include "trace.h"
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#include "qmp-commands.h"
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#include "qapi/qmp/qerror.h"
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#include "qapi/qmp/qjson.h"
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static QEMUBalloonEvent *balloon_event_fn;
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static QEMUBalloonStatus *balloon_stat_fn;
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static void *balloon_opaque;
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static bool balloon_inhibited;
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bool qemu_balloon_is_inhibited(void)
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{
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return balloon_inhibited;
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}
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void qemu_balloon_inhibit(bool state)
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{
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balloon_inhibited = state;
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}
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static bool have_balloon(Error **errp)
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{
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if (kvm_enabled() && !kvm_has_sync_mmu()) {
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error_set(errp, ERROR_CLASS_KVM_MISSING_CAP,
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"Using KVM without synchronous MMU, balloon unavailable");
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return false;
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}
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if (!balloon_event_fn) {
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error_set(errp, ERROR_CLASS_DEVICE_NOT_ACTIVE,
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"No balloon device has been activated");
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return false;
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}
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return true;
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}
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int qemu_add_balloon_handler(QEMUBalloonEvent *event_func,
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QEMUBalloonStatus *stat_func, void *opaque)
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{
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if (balloon_event_fn || balloon_stat_fn || balloon_opaque) {
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/* We're already registered one balloon handler. How many can
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* a guest really have?
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*/
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return -1;
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}
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balloon_event_fn = event_func;
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balloon_stat_fn = stat_func;
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balloon_opaque = opaque;
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return 0;
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}
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void qemu_remove_balloon_handler(void *opaque)
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{
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if (balloon_opaque != opaque) {
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return;
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}
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balloon_event_fn = NULL;
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balloon_stat_fn = NULL;
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balloon_opaque = NULL;
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}
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BalloonInfo *qmp_query_balloon(Error **errp)
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{
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BalloonInfo *info;
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if (!have_balloon(errp)) {
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return NULL;
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}
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info = g_malloc0(sizeof(*info));
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balloon_stat_fn(balloon_opaque, info);
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return info;
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}
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void qmp_balloon(int64_t target, Error **errp)
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{
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if (!have_balloon(errp)) {
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return;
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}
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if (target <= 0) {
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error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "target", "a size");
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return;
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}
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trace_balloon_event(balloon_opaque, target);
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balloon_event_fn(balloon_opaque, target);
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}
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