Peter Xu <pet...@redhat.com> writes: > On Mon, Oct 09, 2023 at 02:25:10PM +0200, Markus Armbruster wrote: >> I apologize for the late reply. > > Not a problem - one week is not even bad at all. :)
I try to keep conversations moving once they started. > [...] > >> > One thing I can do is to move qdev_prop_str_or_null impl (from you) into a >> > separate patch. I can drop some unnecessary changes too when possible, >> > not yet sure what else I can split, but I can try once there. >> >> Suggest to give it a quick try, then see whether you like the resulting >> split better than what you have now. > > OK. > > [...] > >> >> > diff --git a/migration/options.c b/migration/options.c >> >> > index 6bbfd4853d..12e392f68c 100644 >> >> > --- a/migration/options.c >> >> > +++ b/migration/options.c >> >> > @@ -164,9 +164,12 @@ Property migration_properties[] = { >> >> > DEFINE_PROP_SIZE("announce-step", MigrationState, >> >> > parameters.announce_step, >> >> > DEFAULT_MIGRATE_ANNOUNCE_STEP), >> >> > - DEFINE_PROP_STRING("tls-creds", MigrationState, >> >> > parameters.tls_creds), >> >> > - DEFINE_PROP_STRING("tls-hostname", MigrationState, >> >> > parameters.tls_hostname), >> >> > - DEFINE_PROP_STRING("tls-authz", MigrationState, >> >> > parameters.tls_authz), >> >> > + DEFINE_PROP_STR_OR_NULL("tls-creds", MigrationState, >> >> > + parameters.tls_creds), >> >> > + DEFINE_PROP_STR_OR_NULL("tls-hostname", MigrationState, >> >> > + parameters.tls_hostname), >> >> > + DEFINE_PROP_STR_OR_NULL("tls-authz", MigrationState, >> >> > + parameters.tls_authz), >> >> >> >> The qdev machinery now additionally accepts JSON null as property >> >> value. >> >> >> >> If that's undesirable, we need to reject it. >> > >> > I don't think we have a need to pass in null here, not to mention this is >> > only for debugging purpose. >> >> Not sure I understand the bit about debugging. > > The migration_properties here is only used by "-global migration.XXX=YYY". > It's not expected for a normal user to use this interface; one should > normally use QMP or even HMP. So migration_properties as a whole is for > debugging purpose. > >> >> The point I was trying to make is this. Before the patch, we reject >> attempts to set the property value to null. Afterwards, we accept them, >> i.e. the patch loses "reject null property value". If this loss is >> undesirable, we better replace it with suitable hand-written code. > > I don't even know how to set it to NULL before.. as it can only be accessed > via cmdline "-global" as mentioned above, which must be a string anyway. > So I assume this is not an issue. Something like {"execute": "migrate-set-parameters", "arguments": {"tls-authz": null}} Hmm, crashes in migrate_params_apply(), which is a bug. I'm getting more and more suspicious about user-facing migration code... If the migration object is accessible with qom-set, then that's another way to assign null values. >> > The real problem here, IMHO, is current patch will crash if someone >> > specifies -global migration.tls_* fields.. >> >> Trips this assertion: >> >> bool visit_start_alternate(Visitor *v, const char *name, >> GenericAlternate **obj, size_t size, >> Error **errp) >> { >> bool ok; >> >> assert(obj && size >= sizeof(GenericAlternate)); >> assert(!(v->type & VISITOR_OUTPUT) || *obj); >> trace_visit_start_alternate(v, name, obj, size); >> if (!v->start_alternate) { >> ---> assert(!(v->type & VISITOR_INPUT)); >> return true; >> } >> ok = v->start_alternate(v, name, obj, size, errp); >> if (v->type & VISITOR_INPUT) { >> assert(ok != !*obj); >> } >> return ok; >> } >> >> Documented with the start_alternate() method in visitor-impl.h: >> >> /* Must be set by input and clone visitors to visit alternates */ >> bool (*start_alternate)(Visitor *v, const char *name, >> GenericAlternate **obj, size_t size, >> Error **errp); >> >> Known restriction of the string input visitor: >> >> /* >> * The string input visitor does not implement support for visiting >> * QAPI structs, alternates, null, or arbitrary QTypes. Only flat lists >> * of integers (except type "size") are supported. >> */ >> Visitor *string_input_visitor_new(const char *str); >> >> A similar restriction is documented for the string output visitor. >> >> > Unfortunately I'm not an expert on qapi. Markus, does something like this >> > look like a valid fix to you? >> >> I'm not sure whether your simple patch is sufficient for lifting the >> restriction. Needs a deeper think, I'm afraid. Can we make progress on >> the remainder of the series in parallel? > > We can move back to using string rather than StrOrNull, but I saw there's > another email discussing this. Let me also read that first, before jumping > back and forth on the solutions. In my "QAPI string visitors crashes" memo, I demonstrated that the crash on funny property type predates your series. You merely add another instance. Moreover, crashing -global is less serious than a crashing monitor command, because only the latter can take down a running guest. Can't see why your series needs to wait for a fix of the crash bug. Makes sense? > Note that my goal prior to this series is introducing another migration > parameter (avail-switchover-bandwidth). What I think I can do is I'll > proceed with that patch rebasing to master rather than this series; doing > the triplication once more and decouple. Then we can postpone this series. > > Thanks,