Re: [pve-devel] [PATCH v2 qemu-server] dbus-vmstate: fix method call on dbus object resolving to wrong instance

[Fiona Ebner <f.ebner@proxmox.com>]

Am 10.12.25 um 1:20 PM schrieb Fiona Ebner:
> As reported in the community forum [0] and then later by Thomas,
> who provided the relevant system logs, parallel migration with
> '--with-conntrack-state' of multiple VMs may currently lead to a
> crash upon handover:
> 
>> kvm: Unknown savevm section or instance 'dbus-vmstate/dbus-vmstate' 0.
>> Make sure that your current VM setup matches your saved VM setup,
>> including any hotplugged devices
>> kvm: load of migration failed: Invalid argument
> 
> In particular, the following sequence (on my test node)
> 
> pvesh create /nodes/pve9a1/qemu/104/dbus-vmstate --action start
> pvesh create /nodes/pve9a1/qemu/105/dbus-vmstate --action start
> pvesh create /nodes/pve9a1/qemu/105/dbus-vmstate --action stop
> 
> results in the wrong service being shut down (note the unexpected ID
> in the last line!):
> 
> Dec 10 10:07:40 pve9a1 pvesh[30453]: starting dbus-vmstate helper for VM 104
> Dec 10 10:07:40 pve9a1 systemd[1]: Starting pve-dbus-vmstate@104.service - PVE DBus VMState Helper (VM 104)...
> Dec 10 10:07:41 pve9a1 dbus-vmstate[30456]: pve-vmstate-104 listening on :1.55
> Dec 10 10:07:41 pve9a1 systemd[1]: Started pve-dbus-vmstate@104.service - PVE DBus VMState Helper (VM 104).
> Dec 10 10:07:44 pve9a1 pvesh[30511]: starting dbus-vmstate helper for VM 105
> Dec 10 10:07:44 pve9a1 systemd[1]: Starting pve-dbus-vmstate@105.service - PVE DBus VMState Helper (VM 105)...
> Dec 10 10:07:45 pve9a1 dbus-vmstate[30573]: pve-vmstate-105 listening on :1.58
> Dec 10 10:07:45 pve9a1 systemd[1]: Started pve-dbus-vmstate@105.service - PVE DBus VMState Helper (VM 105).
> Dec 10 10:07:48 pve9a1 pvesh[30595]: stopping dbus-vmstate helper for VM 105
> Dec 10 10:07:48 pve9a1 dbus-vmstate[30456]: shutting down gracefully ..
> Dec 10 10:07:48 pve9a1 systemd[1]: pve-dbus-vmstate@104.service: Deactivated successfully.
> 
> So the dbus-vmstate object is removed from the wrong VM before loading
> the migration state. Note that the crash is still racy, because if the
> dbus-vmstate is removed on the source side for the same wrong VM before
> the migration handover, the QEMU objects for both instances will still
> match.
> 
> To fix the issue, introduce a dbus_call_method() helper similar to the
> already existing dbus_get_property() one. Like, this the owner is
> respected even if there are multiple (queued) owners on the DBus.
> 
> [0]: https://forum.proxmox.com/threads/176821/post-820775
> 

Fixes: dc76a590 ("fix #5180: migrate: integrate helper for
live-migrating conntrack info")

> Reported-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
> Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>


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