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>
29 lines
690 B
C
29 lines
690 B
C
/*
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* Balloon
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*
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* Copyright IBM, Corp. 2008
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*
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* Authors:
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* Anthony Liguori <aliguori@us.ibm.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2. See
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* the COPYING file in the top-level directory.
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*
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*/
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#ifndef _QEMU_BALLOON_H
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#define _QEMU_BALLOON_H
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#include "qapi-types.h"
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typedef void (QEMUBalloonEvent)(void *opaque, ram_addr_t target);
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typedef void (QEMUBalloonStatus)(void *opaque, BalloonInfo *info);
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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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void qemu_remove_balloon_handler(void *opaque);
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bool qemu_balloon_is_inhibited(void);
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void qemu_balloon_inhibit(bool state);
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#endif
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