managed-startup.rst (1602B)
1 Managed start up options 2 ======================== 3 4 In system mode emulation, it's possible to create a VM in a paused 5 state using the ``-S`` command line option. In this state the machine 6 is completely initialized according to command line options and ready 7 to execute VM code but VCPU threads are not executing any code. The VM 8 state in this paused state depends on the way QEMU was started. It 9 could be in: 10 11 - initial state (after reset/power on state) 12 - with direct kernel loading, the initial state could be amended to execute 13 code loaded by QEMU in the VM's RAM and with incoming migration 14 - with incoming migration, initial state will be amended with the migrated 15 machine state after migration completes 16 17 This paused state is typically used by users to query machine state and/or 18 additionally configure the machine (by hotplugging devices) in runtime before 19 allowing VM code to run. 20 21 However, at the ``-S`` pause point, it's impossible to configure options 22 that affect initial VM creation (like: ``-smp``/``-m``/``-numa`` ...) or 23 cold plug devices. The experimental ``--preconfig`` command line option 24 allows pausing QEMU before the initial VM creation, in a "preconfig" state, 25 where additional queries and configuration can be performed via QMP 26 before moving on to the resulting configuration startup. In the 27 preconfig state, QEMU only allows a limited set of commands over the 28 QMP monitor, where the commands do not depend on an initialized 29 machine, including but not limited to: 30 31 - ``qmp_capabilities`` 32 - ``query-qmp-schema`` 33 - ``query-commands`` 34 - ``query-status`` 35 - ``x-exit-preconfig``