On 23.07.2025 08:55, Jürgen Groß wrote: > On 23.07.25 08:43, Jan Beulich wrote: >> On 23.07.2025 08:34, Jürgen Groß wrote: >>> On 23.07.25 08:28, Jan Beulich wrote: >>>> On 22.07.2025 02:19, Jason Andryuk wrote: >>>>> --- a/xen/common/domain.c >>>>> +++ b/xen/common/domain.c >>>>> @@ -195,6 +195,14 @@ static void set_domain_state_info(struct >>>>> xen_domctl_get_domain_state *info, >>>>> info->state |= XEN_DOMCTL_GETDOMSTATE_STATE_DYING; >>>>> if ( d->is_dying == DOMDYING_dead ) >>>>> info->state |= XEN_DOMCTL_GETDOMSTATE_STATE_DEAD; >>>>> + >>>>> + info->caps = 0; >>>>> + if ( is_control_domain(d) ) >>>>> + info->caps |= XEN_DOMCTL_GETDOMSTATE_CAP_CONTROL; >>>>> + if ( is_hardware_domain(d) ) >>>>> + info->caps |= XEN_DOMCTL_GETDOMSTATE_CAP_HARDWARE; >>>>> + if ( is_xenstore_domain(d) ) >>>>> + info->caps |= XEN_DOMCTL_GETDOMSTATE_CAP_XENSTORE; >>>>> info->unique_id = d->unique_id; >>>>> } >>>> >>>> This being a stable sub-op, don't we need a way to indicate to the caller >>>> _that_ this field has valid data now? When non-zero it's easy to tell, but >>>> getting back zero is ambiguous. >>> >>> The hypercall sub-op was introduced in this development cycle only, so >>> there is no released Xen hypervisor without the capability setting. >>> >>> In case this patch doesn't make it into 4.21, the case you are mentioning >>> must be handled, of course. >> >> Hmm, yes, this way it's on the edge. As a stable sub-op, someone could have >> backported the change, though. IOW (and in general) I wonder whether for >> stable sub-ops we shouldn't be pretty strict about functional extensions, >> not tying their addition to releases at all. > > Should we really care about downstreams backporting not yet released > functionality? > > Using your reasoning this would mean we'd need to issue XSAs for not yet > released hypervisor issues of stable interfaces, too. I don't think we > want to do that.
To me, the latter doesn't necessarily follow from the former. But anyway, I'm not going to insist, but I wanted the situation to at least be considered. In particular also forward-looking, when we may gain more stable sub-ops. At some point it may turn out necessary to backport such even into upstream branches. Jan
