On Fri, Jun 07, 2024 at 11:09:37AM +0200, David Hildenbrand wrote: > We currently initialize the memmap such that PG_reserved is set and the > refcount of the page is 1. In virtio-mem code, we have to manually clear > that PG_reserved flag to make memory offlining with partially hotplugged > memory blocks possible: has_unmovable_pages() would otherwise bail out on > such pages. > > We want to avoid PG_reserved where possible and move to typed pages > instead. Further, we want to further enlighten memory offlining code about > PG_offline: offline pages in an online memory section. One example is > handling managed page count adjustments in a cleaner way during memory > offlining. > > So let's initialize the pages with PG_offline instead of PG_reserved. > generic_online_page()->__free_pages_core() will now clear that flag before > handing that memory to the buddy. > > Note that the page refcount is still 1 and would forbid offlining of such > memory except when special care is take during GOING_OFFLINE as > currently only implemented by virtio-mem. > > With this change, we can now get non-PageReserved() pages in the XEN > balloon list. From what I can tell, that can already happen via > decrease_reservation(), so that should be fine. > > HV-balloon should not really observe a change: partial online memory > blocks still cannot get surprise-offlined, because the refcount of these > PageOffline() pages is 1. > > Update virtio-mem, HV-balloon and XEN-balloon code to be aware that > hotplugged pages are now PageOffline() instead of PageReserved() before > they are handed over to the buddy. > > We'll leave the ZONE_DEVICE case alone for now. > > Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> Acked-by: Oscar Salvador <osalvador@xxxxxxx> # for the generic memory-hotplug bits -- Oscar Salvador SUSE Labs
