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cpus: stop vm in suspended runstate

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Currently, a vm in the suspended state is not completely stopped.  The VCPUs
have been paused, but the cpu clock still runs, and runstate notifiers for
the transition to stopped have not been called.  This causes problems for
live migration.  Stale cpu timers_state is saved to the migration stream,
causing time errors in the guest when it wakes from suspend, and state that
would have been modified by runstate notifiers is wrong.

Modify vm_stop to completely stop the vm if the current state is suspended,
transition to RUN_STATE_PAUSED, and remember that the machine was suspended.
Modify vm_start to restore the suspended state.

This affects all callers of vm_stop and vm_start, notably, the qapi stop and
cont commands:

  old behavior:
    RUN_STATE_SUSPENDED --> stop --> RUN_STATE_SUSPENDED

  new behavior:
    RUN_STATE_SUSPENDED --> stop --> RUN_STATE_PAUSED
    RUN_STATE_PAUSED    --> cont --> RUN_STATE_SUSPENDED

For example:

    (qemu) info status
    VM status: paused (suspended)

    (qemu) stop
    (qemu) info status
    VM status: paused

    (qemu) system_wakeup
    Error: Unable to wake up: guest is not in suspended state

    (qemu) cont
    (qemu) info status
    VM status: paused (suspended)

    (qemu) system_wakeup
    (qemu) info status
    VM status: running

Suggested-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Link: https://lore.kernel.org/r/1704312341-66640-3-git-send-email-steven.sistare@oracle.com
Signed-off-by: Peter Xu <peterx@redhat.com>
This commit is contained in:
Steve Sistare 2024-01-03 12:05:31 -08:00 • committed by Peter Xu
parent f06f316d3e
commit b9ae473d80
5 changed files with 39 additions and 13 deletions
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11
qapi/misc.json
View file

@ -134,7 +134,7 @@
##
# @stop:
#
# Stop all guest VCPU execution.
# Stop guest VM execution.
#
# Since: 0.14
#
@ -143,6 +143,9 @@
# the guest remains paused once migration finishes, as if the -S
# option was passed on the command line.
#
# In the "suspended" state, it will completely stop the VM and
# cause a transition to the "paused" state. (Since 9.0)
#
# Example:
#
# -> { "execute": "stop" }
@ -153,7 +156,7 @@
##
# @cont:
#
# Resume guest VCPU execution.
# Resume guest VM execution.
#
# Since: 0.14
#
@ -165,6 +168,10 @@
# guest starts once migration finishes, removing the effect of the
# -S command line option if it was passed.
#
# If the VM was previously suspended, and not been reset or woken,
# this command will transition back to the "suspended" state.
# (Since 9.0)
#
# Example:
#
# -> { "execute": "cont" }

6
qapi/run-state.json
View file

@ -102,7 +102,7 @@
##
# @StatusInfo:
#
# Information about VCPU run state
# Information about VM run state
#
# @running: true if all VCPUs are runnable, false if not runnable
#
@ -130,9 +130,9 @@
##
# @query-status:
#
# Query the run status of all VCPUs
# Query the run status of the VM
#
# Returns: @StatusInfo reflecting all VCPUs
# Returns: @StatusInfo reflecting the VM
#
# Since: 0.14
#