Commit 62e9dc35 authored by Sergio Lopez's avatar Sergio Lopez Committed by Paolo Bonzini
Browse files

docs/microvm.rst: add instructions for shutting down the guest 



Add a new section explaining the particularities of the microvm
machine type for triggering a guest-initiated shut down.

Signed-off-by: default avatarSergio Lopez <slp@redhat.com>
Message-Id: <20191115161338.42864-3-slp@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent ff9d7089

docs/microvm.rst

+21 −0
Original line number Diff line number Diff line
@@ -106,3 +106,24 @@ disabled:: 
     -device virtio-blk-device,drive=test \

     -netdev tap,id=tap0,script=no,downscript=no \

     -device virtio-net-device,netdev=tap0





Triggering a guest-initiated shut down

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~



As the microvm machine type includes just a small set of system

devices, some x86 mechanisms for rebooting or shutting down the

system, like sending a key sequence to the keyboard or writing to an

ACPI register, doesn't have any effect in the VM.



The recommended way to trigger a guest-initiated shut down is by

generating a ``triple-fault``, which will cause the VM to initiate a

reboot. Additionally, if the ``-no-reboot`` argument is present in the

command line, QEMU will detect this event and terminate its own

execution gracefully.



Linux does support this mechanism, but by default will only be used

after other options have been tried and failed, causing the reboot to

be delayed by a small number of seconds. It's possible to instruct it

to try the triple-fault mechanism first, by adding ``reboot=t`` to the

kernel's command line.