* Peter Xu (pet...@redhat.com) wrote:
> It was allowed in the past to even cancel a postcopy migration, but it
> does not really make sense, and no one should be using it, since
> cancelling a migration during postcopy means crashing the VM at no time.
>
> Let's just use re-use this command as a way to pause the postcopy
> migration when we detected that we are in postcopy migration. This can
> be used when we want to trigger the postcopy recovery manually.
>
> Signed-off-by: Peter Xu <pet...@redhat.com>
Yes, OK, this is a little odd without having any flags or anything, but
it's essentially the saem reason that cancel exists - to stop a
migration we know that's broken for some reason.
(I could argue whether this should be special cased in migrate_fd_cancel
instead, but that's just a preference).
Reviewed-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
> hmp-commands.hx | 8 ++++++--
> migration/migration.c | 18 +++++++++++++++++-
> qapi/migration.json | 3 ++-
> 3 files changed, 25 insertions(+), 4 deletions(-)
>
> diff --git a/hmp-commands.hx b/hmp-commands.hx
> index ffcdc34652..32fdd52212 100644
> --- a/hmp-commands.hx
> +++ b/hmp-commands.hx
> @@ -952,14 +952,18 @@ ETEXI
> .name = "migrate_cancel",
> .args_type = "",
> .params = "",
> - .help = "cancel the current VM migration",
> + .help = "cancel the current VM precopy migration, or "
> + "pause the migration if it's in postcopy state, "
> + "so that a postcopy recovery can be carried out
> later.",
> .cmd = hmp_migrate_cancel,
> },
>
> STEXI
> @item migrate_cancel
> @findex migrate_cancel
> -Cancel the current VM migration.
> +If during a precopy, this command cancels the migration. If during
> +postcopy, this command pauses the migration (so that a postcopy
> +recovery can be carried out afterward).
> ETEXI
>
> {
> diff --git a/migration/migration.c b/migration/migration.c
> index 8762fad9be..0c1a783df2 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -1535,7 +1535,23 @@ void qmp_migrate(const char *uri, bool has_blk, bool
> blk,
>
> void qmp_migrate_cancel(Error **errp)
> {
> - migrate_fd_cancel(migrate_get_current());
> + MigrationState *ms = migrate_get_current();
> + int ret;
> +
> + if (ms->state == MIGRATION_STATUS_POSTCOPY_ACTIVE) {
> + /*
> + * Cancelling a postcopy migration does not really make sense.
> + * Here instead we pause the migration only, so another
> + * recovery can take place if needed.
> + */
> + ret = qemu_file_shutdown(ms->to_dst_file);
> + if (ret) {
> + error_setg(errp, "Failed to pause migration stream.");
> + }
> + return;
> + }
> +
> + migrate_fd_cancel(ms);
> }
>
> void qmp_migrate_continue(MigrationStatus state, Error **errp)
> diff --git a/qapi/migration.json b/qapi/migration.json
> index 5dfac0681d..e15bb516cd 100644
> --- a/qapi/migration.json
> +++ b/qapi/migration.json
> @@ -881,7 +881,8 @@
> ##
> # @migrate_cancel:
> #
> -# Cancel the current executing migration process.
> +# Cancel the current executing migration process for precopy. For
> +# postcopy, it'll pause the migration instead.
> #
> # Returns: nothing on success
> #
> --
> 2.14.3
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
