Re: [Qemu-devel] [PATCH v2 07/11] migration: check global params for validity

[Peter Xu]

On Mon, Jul 17, 2017 at 03:25:05PM -0300, Eduardo Habkost wrote:
> On Mon, Jul 17, 2017 at 04:26:07PM +0800, Peter Xu wrote:
> > Adding validity check for the migration parameters passed in via global
> > properties.
> > 
> > Signed-off-by: Peter Xu <address@hidden>
> > ---
> >  migration/migration.c | 34 ++++++++++++++++++++++++++++++++++
> >  1 file changed, 34 insertions(+)
> > 
> > diff --git a/migration/migration.c b/migration/migration.c
> > index 8c65054..5a7f22c 100644
> > --- a/migration/migration.c
> > +++ b/migration/migration.c
> > @@ -2109,6 +2109,39 @@ static void migration_instance_init(Object *obj)
> >      ms->parameters.tls_hostname = g_strdup("");
> >  }
> >  
> > +static void migration_instance_post_init(Object *obj)
> > +{
> > +    MigrationState *ms = (MigrationState *)obj;
> > +    Error *err = NULL;
> > +    MigrationParameters params = {
> > +        .has_compress_level = true,
> > +        .compress_level = ms->parameters.compress_level,
> > +        .has_compress_threads = true,
> > +        .compress_threads = ms->parameters.compress_threads,
> > +        .has_decompress_threads = true,
> > +        .decompress_threads = ms->parameters.decompress_threads,
> > +        .has_cpu_throttle_initial = true,
> > +        .cpu_throttle_initial = ms->parameters.cpu_throttle_initial,
> > +        .has_cpu_throttle_increment = true,
> > +        .cpu_throttle_increment = ms->parameters.cpu_throttle_increment,
> > +        .has_max_bandwidth = true,
> > +        .max_bandwidth = ms->parameters.max_bandwidth,
> > +        .has_downtime_limit = true,
> > +        .downtime_limit = ms->parameters.downtime_limit,
> > +        .has_x_checkpoint_delay = true,
> > +        .x_checkpoint_delay = ms->parameters.x_checkpoint_delay,
> > +        .has_block_incremental = true,
> > +        .block_incremental = ms->parameters.block_incremental,
> > +    };
> > +
> > +    /* We have applied all the migration properties... */
> > +
> > +    if (!migrate_params_check(&params, &err)) {
> 
> Why not just:
>   if (!migrate_params_check(&ms->parameters, &err))
> ?
> 
> If the ms->parameters.has_* fields are not set to true anywhere,
> we can set them to true in instance_init.

Sure.

> 
> (This would also also us to use QAPI_CLONE in
> qmp_query_migrate_parameters() instead of manually copying each
> field.
> 
> 
> > +        error_report_err(err);
> > +        exit(1);
> > +    }
> > +}
> 
> On real devices, this is normally done on realize (which has
> proper error reporting).  We never realize the TYPE_MIGRATION
> object because it's not a real device, though.

Hmm...

> 
> Doing error checks on post_init feels fragile, as the only way
> errors can be handled is triggering exit(1) in the middle of an
> object_new() call.
> 
> As we have only one place where the TYPE_MIGRATION object is
> created, I suggest calling migrate_params_check() inside
> migration_object_init().

... How about I just provide a realize() for it? Then I can drop the
QOM patch 4, also, I can keep the checks along with the object itself.

Thanks,

-- 
Peter Xu