On Tue, Dec 16, 2025 at 10:19 AM Mike Rapoport <[email protected]> wrote:
>
> On Tue, Dec 16, 2025 at 10:05:27AM -0500, Pasha Tatashin wrote:
> > > > +static struct page *__init kho_get_preserved_page(phys_addr_t phys,
> > > > + unsigned int order)
> > > > +{
> > > > + unsigned long pfn = PHYS_PFN(phys);
> > > > + int nid = early_pfn_to_nid(pfn);
> > > > +
> > > > + for (int i = 0; i < (1 << order); i++)
> > > > + init_deferred_page(pfn + i, nid);
> > >
> > > This will skip pages below node->first_deferred_pfn, we need to use
> > > __init_page_from_nid() here.
> >
> > Mike, but those struct pages should be initialized early anyway. If
> > they are not yet initialized we have a problem, as they are going to
> > be re-initialized later.
>
> Can say I understand your point. Which pages should be initialized earlt?
All pages below node->first_deferred_pfn.
> And which pages will be reinitialized?
kho_memory_init() is called after free_area_init() (which calls
memmap_init_range to initialize low memory struct pages). So, if we
use __init_page_from_nid() as suggested, we would be blindly running
__init_single_page() again on those low-memory pages that
memmap_init_range() already set up. This would cause double
initialization and corruptions due to losing the order information.
> > > > +
> > > > + return pfn_to_page(pfn);
> > > > +}
> > > > +
> > > > static void __init deserialize_bitmap(unsigned int order,
> > > > struct khoser_mem_bitmap_ptr *elm)
> > > > {
> > > > @@ -449,7 +466,7 @@ static void __init deserialize_bitmap(unsigned int
> > > > order,
> > > > int sz = 1 << (order + PAGE_SHIFT);
> > > > phys_addr_t phys =
> > > > elm->phys_start + (bit << (order + PAGE_SHIFT));
> > > > - struct page *page = phys_to_page(phys);
> > > > + struct page *page = kho_get_preserved_page(phys, order);
> > >
> > > I think it's better to initialize deferred struct pages later in
> > > kho_restore_page. deserialize_bitmap() runs before SMP and it already does
> >
> > The KHO memory should still be accessible early in boot, right?
>
> The memory is accessible. And we anyway should not use struct page for
> preserved memory before kho_restore_{folio,pages}.
This makes sense, what happens if someone calls kho_restore_folio()
before deferred pages are initialized?
