On Tue, 23 Oct 2012 14:54:21 +0200
Paolo Bonzini <pbonz...@redhat.com> wrote:
> Right now, stop followed by an incoming migration will let the
> virtual machine start. cont before an incoming migration instead
> will fail.
>
> This is bad because the actual behavior is not predictable; it is
> racy with respect to the start of the incoming migration. That's
> because incoming migration is blocking, and thus will delay the
> processing of stop/cont until the end of the migration.
>
> In addition, there's nothing that really prevents the user from
> typing the block device's passwords before incoming migration is
> done, so returning the DeviceEncrypted error is also helpful in
> the QMP case.
>
> Both things can be fixed by just toggling the autostart variable when
> stop/cont are called in INMIGRATE state.
>
> Note that libvirt is currently working around the race by looping
> if the MigrationExpected answer is returned. After this patch, the
> command will return right away without ever raising an error.
>
> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
Applied series to the qmp branch, thanks.
> ---
> qapi-schema.json | 23 ++++++++++++++---------
> qerror.h | 3 ---
> qmp.c | 17 +++++++++++------
> 3 file modificati, 25 inserzioni(+), 18 rimozioni(-)
>
> diff --git a/qapi-schema.json b/qapi-schema.json
> index c615ee2..6b14edc 100644
> --- a/qapi-schema.json
> +++ b/qapi-schema.json
> @@ -22,15 +22,11 @@
> # @KVMMissingCap: the requested operation can't be fulfilled because a
> # required KVM capability is missing
> #
> -# @MigrationExpected: the requested operation can't be fulfilled because a
> -# migration process is expected
> -#
> # Since: 1.2
> ##
> { 'enum': 'ErrorClass',
> 'data': [ 'GenericError', 'CommandNotFound', 'DeviceEncrypted',
> - 'DeviceNotActive', 'DeviceNotFound', 'KVMMissingCap',
> - 'MigrationExpected' ] }
> + 'DeviceNotActive', 'DeviceNotFound', 'KVMMissingCap' ] }
>
> ##
> # @add_client
> @@ -149,7 +145,11 @@
> #
> # @finish-migrate: guest is paused to finish the migration process
> #
> -# @inmigrate: guest is paused waiting for an incoming migration
> +# @inmigrate: guest is paused waiting for an incoming migration. Note
> +# that this state does not tell whether the machine will start at the
> +# end of the migration. This depends on the command-line -S option and
> +# any invocation of 'stop' or 'cont' that has happened since QEMU was
> +# started.
> #
> # @internal-error: An internal error that prevents further guest execution
> # has occurred
> @@ -1210,7 +1210,9 @@
> # Since: 0.14.0
> #
> # Notes: This function will succeed even if the guest is already in the
> stopped
> -# state
> +# state. In "inmigrate" state, it will ensure that the guest
> +# remains paused once migration finishes, as if the -S option was
> +# passed on the command line.
> ##
> { 'command': 'stop' }
>
> @@ -1299,11 +1301,14 @@
> # Since: 0.14.0
> #
> # Returns: If successful, nothing
> -# If the QEMU is waiting for an incoming migration,
> MigrationExpected
> # If QEMU was started with an encrypted block device and a key has
> # not yet been set, DeviceEncrypted.
> #
> -# Notes: This command will succeed if the guest is currently running.
> +# Notes: This command will succeed if the guest is currently running. It
> +# will also succeed if the guest is in the "inmigrate" state; in
> +# this case, the effect of the command is to make sure the guest
> +# starts once migration finishes, removing the effect of the -S
> +# command line option if it was passed.
> ##
> { 'command': 'cont' }
>
> diff --git a/qerror.h b/qerror.h
> index c91708c..5e98a39 100644
> --- a/qerror.h
> +++ b/qerror.h
> @@ -165,9 +165,6 @@ void assert_no_error(Error *err);
> #define QERR_MIGRATION_NOT_SUPPORTED \
> ERROR_CLASS_GENERIC_ERROR, "State blocked by non-migratable device '%s'"
>
> -#define QERR_MIGRATION_EXPECTED \
> - ERROR_CLASS_MIGRATION_EXPECTED, "An incoming migration is expected
> before this command can be executed"
> -
> #define QERR_MISSING_PARAMETER \
> ERROR_CLASS_GENERIC_ERROR, "Parameter '%s' is missing"
>
> diff --git a/qmp.c b/qmp.c
> index 36c54c5..2c8d559 100644
> --- a/qmp.c
> +++ b/qmp.c
> @@ -85,7 +85,11 @@ void qmp_quit(Error **err)
>
> void qmp_stop(Error **errp)
> {
> - vm_stop(RUN_STATE_PAUSED);
> + if (runstate_check(RUN_STATE_INMIGRATE)) {
> + autostart = 0;
> + } else {
> + vm_stop(RUN_STATE_PAUSED);
> + }
> }
>
> void qmp_system_reset(Error **errp)
> @@ -144,10 +148,7 @@ void qmp_cont(Error **errp)
> {
> Error *local_err = NULL;
>
> - if (runstate_check(RUN_STATE_INMIGRATE)) {
> - error_set(errp, QERR_MIGRATION_EXPECTED);
> - return;
> - } else if (runstate_check(RUN_STATE_INTERNAL_ERROR) ||
> + if (runstate_check(RUN_STATE_INTERNAL_ERROR) ||
> runstate_check(RUN_STATE_SHUTDOWN)) {
> error_set(errp, QERR_RESET_REQUIRED);
> return;
> @@ -162,7 +163,11 @@ void qmp_cont(Error **errp)
> return;
> }
>
> - vm_start();
> + if (runstate_check(RUN_STATE_INMIGRATE)) {
> + autostart = 1;
> + } else {
> + vm_start();
> + }
> }
>
> void qmp_system_wakeup(Error **errp)
