a3eae205c6
Add the cpr-exec migration mode. Usage:
qemu-system-$arch -machine aux-ram-share=on ...
migrate_set_parameter mode cpr-exec
migrate_set_parameter cpr-exec-command \
<arg1> <arg2> ... -incoming <uri-1> \
migrate -d <uri-1>
The migrate command stops the VM, saves state to uri-1,
directly exec's a new version of QEMU on the same host,
replacing the original process while retaining its PID, and
loads state from uri-1. Guest RAM is preserved in place,
albeit with new virtual addresses.
The new QEMU process is started by exec'ing the command
specified by the @cpr-exec-command parameter. The first word of
the command is the binary, and the remaining words are its
arguments. The command may be a direct invocation of new QEMU,
or may be a non-QEMU command that exec's the new QEMU binary.
This mode creates a second migration channel that is not visible
to the user. At the start of migration, old QEMU saves CPR state
to the second channel, and at the end of migration, it tells the
main loop to call cpr_exec. New QEMU loads CPR state early, before
objects are created.
Because old QEMU terminates when new QEMU starts, one cannot
stream data between the two, so uri-1 must be a type,
such as a file, that accepts all data before old QEMU exits.
Otherwise, old QEMU may quietly block writing to the channel.
Memory-backend objects must have the share=on attribute, but
memory-backend-epc is not supported. The VM must be started with
the '-machine aux-ram-share=on' option, which allows anonymous
memory to be transferred in place to the new process. The memfds
are kept open across exec by clearing the close-on-exec flag, their
values are saved in CPR state, and they are mmap'd in new QEMU.
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Link: https://lore.kernel.org/r/1759332851-370353-7-git-send-email-steven.sistare@oracle.com
Signed-off-by: Peter Xu <peterx@redhat.com>
63 lines
1.9 KiB
C
63 lines
1.9 KiB
C
/*
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* Copyright (c) 2021, 2024 Oracle and/or its affiliates.
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or later.
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* See the COPYING file in the top-level directory.
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*/
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#ifndef MIGRATION_CPR_H
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#define MIGRATION_CPR_H
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#include "qapi/qapi-types-migration.h"
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#include "qemu/queue.h"
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#define MIG_MODE_NONE -1
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#define QEMU_CPR_FILE_MAGIC 0x51435052
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#define QEMU_CPR_FILE_VERSION 0x00000001
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#define CPR_STATE "CprState"
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typedef QLIST_HEAD(CprFdList, CprFd) CprFdList;
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typedef QLIST_HEAD(CprVFIODeviceList, CprVFIODevice) CprVFIODeviceList;
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typedef struct CprState {
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CprFdList fds;
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CprVFIODeviceList vfio_devices;
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} CprState;
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extern CprState cpr_state;
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void cpr_save_fd(const char *name, int id, int fd);
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void cpr_delete_fd(const char *name, int id);
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int cpr_find_fd(const char *name, int id);
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void cpr_resave_fd(const char *name, int id, int fd);
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int cpr_open_fd(const char *path, int flags, const char *name, int id,
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Error **errp);
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typedef bool (*cpr_walk_fd_cb)(int fd);
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bool cpr_walk_fd(cpr_walk_fd_cb cb);
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MigMode cpr_get_incoming_mode(void);
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void cpr_set_incoming_mode(MigMode mode);
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bool cpr_is_incoming(void);
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int cpr_state_save(MigrationChannel *channel, Error **errp);
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int cpr_state_load(MigrationChannel *channel, Error **errp);
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void cpr_state_close(void);
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struct QIOChannel *cpr_state_ioc(void);
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bool cpr_incoming_needed(void *opaque);
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int cpr_get_fd_param(const char *name, const char *fdname, int index,
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Error **errp);
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QEMUFile *cpr_transfer_output(MigrationChannel *channel, Error **errp);
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QEMUFile *cpr_transfer_input(MigrationChannel *channel, Error **errp);
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void cpr_exec_init(void);
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QEMUFile *cpr_exec_output(Error **errp);
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QEMUFile *cpr_exec_input(Error **errp);
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void cpr_exec_persist_state(QEMUFile *f);
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bool cpr_exec_has_state(void);
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void cpr_exec_unpersist_state(void);
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void cpr_exec_unpreserve_fds(void);
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#endif
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