On Tue, Aug 05, 2025 at 04:22:32PM +0200, David Hildenbrand wrote: > On 05.08.25 16:20, Jason Gunthorpe wrote: > > On Tue, Aug 05, 2025 at 04:10:45PM +0200, David Hildenbrand wrote: > > > There are some weird scenarios where you hotplug memory after boot memory, > > > and suddenly you can runtime-allocate a gigantic folio that spans both > > > ranges etc. > > > > I was thinking we'd forbid this directly, but yes it is a another new > > check. > > > > > So while related, the corner cases are all a bit nasty, and just forbidding > > > folios to span a memory section on these problematic configs (sparse > > > !vmemmap) sounds interesting. > > > > Indeed, this just sounds like forcing MAX_ORDER to be no larger than > > the section size for this old mode? > > MAX_ORDER is always limited to the section size already. > > MAX_ORDER is only about buddy allocations. What hugetlb and dax do is > independent of MAX_ORDER. Oh I thought it limited folios too. Still same idea is to have a MAX_FOLIO_ORDER for that case. Jason
