migrate_set_error(s, err) stores a copy of @err in @s. The original
@err is not freed. Most callers free it immediately. Some callers
free it later, or pass it on. And some leak it. Fix those.
Perhaps migrate_set_error(s, err) should take ownership of @err. The
callers that free it immediately would become simpler, and avoid a
copy and a deallocation. The others would have to pass
error_copy(err).
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Link: https://lore.kernel.org/r/20251115083500.2753895-2-armbru@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Per reported and analyzed by Peter:
https://lore.kernel.org/r/CAFEAcA_mUQ2NeoguR5efrhw7XYGofnriWEA=+Dg+Ocvyam1wAw@mail.gmail.com
mfd leak is a false positive, try to use a coverity annotation (which I
didn't find manual myself, but still give it a shot).
Fix the other one by capture error if setenv() failed. When at it, pass
the error to the top (cpr_state_save()). Along the way, changing all
retval to bool when errp is around.
Resolves: Coverity CID 1641391
Resolves: Coverity CID 1641392
Fixes: efc6587313 ("migration: cpr-exec save and load")
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20251021220407.2662288-3-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
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>
To preserve CPR state across exec, create a QEMUFile based on a memfd, and
keep the memfd open across exec. Save the value of the memfd in an
environment variable so post-exec QEMU can find it.
These new functions are called in a subsequent patch.
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Link: https://lore.kernel.org/r/1759332851-370353-6-git-send-email-steven.sistare@oracle.com
[peterx: fix build for Windows]
Signed-off-by: Peter Xu <peterx@redhat.com>
