On 20.02.2018 15:57, Cornelia Huck wrote: > On Tue, 20 Feb 2018 13:16:37 +0100 > David Hildenbrand <da...@redhat.com> wrote: > >> On 20.02.2018 13:05, Christian Borntraeger wrote: >>> >>> >>> On 02/19/2018 06:42 PM, David Hildenbrand wrote: >>>> From an architecture point of view, nothing can be mapped into the address >>>> space on s390x. All there is is memory. Therefore there is also not really >>>> an interface to communicate such information to the guest. All we can do is >>>> specify the maximum ram address and guests can probe in that range if >>>> memory is available and usable (TPROT). >>> >>> In fact there is an interface in SCLP that describes the memory sizes >>> (maximum in >>> read scp info) and the details (read_storage_element0_info). I am asking >>> myself >>> if we should re-introduce read_storage_element_info and use that to avoid >>> tprot >> >> Yes, we could do that (basically V1 of this patch) but have to glue it >> to the a compatibility machine then. > > Actually, this makes quite a bit of sense (introduce the interface for > everyone in 2.12 and turn it off in compat machines).
Jup, either 2.12 or 2.13, no need to hurry. > > Does real hardware have configurations where you can get the memory > sizes, but not the attach/deattach support? (Hardware with the feature, > but no standby memory defined?) I would guess that "0" for standby memory is valid but only people with access to documentation can answer that :) >> Interesting, didn't know about that. Will rephrase then to >> >> "While the hypervisor can deny to online an increment, all increments >> have to be predefined and there is no way of telling the guest about a >> newly "hotplugged" increment." > > Rephrase which part? :) "And nobody can really hinder it from doing so." Thanks! -- Thanks, David / dhildenb
