On 06.12.16 17:38:11, Will Deacon wrote: > On Mon, Dec 05, 2016 at 03:42:14PM +0000, Ard Biesheuvel wrote: > > On 2 December 2016 at 14:49, James Morse <james.mo...@arm.com> wrote: > > > Patch "arm64: mm: Fix memmap to be initialized for the entire section" > > > changes pfn_valid() in a way that breaks hibernate. These patches fix > > > hibernate, and provided struct page's are allocated for nomap pages, > > > can be applied before [0]. > > > > > > Hibernate core code belives 'valid' to mean "I can access this". It > > > uses pfn_valid() to test the page if the page is 'valid'. > > > > > > pfn_valid() needs to be changed so that all struct pages in a numa > > > node have the same node-id. Currently 'nomap' pages are skipped, and > > > retain their pre-numa node-ids, which leads to a later BUG_ON(). > > > > > > These patches make hibernate's savable_page() take its escape route > > > via 'if (PageReserved(page) && pfn_is_nosave(pfn))'. > > > > > > > This makes me feel slightly uneasy. Robert makes a convincing point, > > but I wonder if we can expect more fallout from the ambiguity of > > pfn_valid(). Now we are not only forced to assign non-existing (as far > > as the OS is concerned) pages to the correct NUMA node, we also need > > to set certain page flags. > > Yes, I really don't know how to proceed here. Playing whack-a-mole with > pfn_valid() users doesn't sounds like an improvement on the current > situation to me. > > Robert -- if we leave pfn_valid() as it is, would a point-hack to > memmap_init_zone help, or do you anticipate other problems?
I would suggest to fix the hibernation code as I commented on before to use pfn_is_nosave() that defaults to pfn_valid() but uses memblock_ is_nomap() for arm64. Let's just fix it and see if no other issues arise. I am trying to send a patch for this until tomorrow. I am also going to see how early_pfn_valid() could be redirected to use memblock_is_nomap() on arm64. That would "quick fix" the problem, though I rather prefer to go further with the current solution. -Robert
