On Mon 04-01-21 17:30:48, David Hildenbrand wrote: > >> Let's assume this is indeed a reserved pfn in the altmap. What's the > >> actual address of the memmap? > > > > Not sure what exactly you are asking for but crash says > > crash> kmem -p 6060000 > > PAGE PHYSICAL MAPPING INDEX CNT FLAGS > > fffff8c600181800 6060000 0 0 0 fffffc0000000 > > ^ this looks like it was somewhat initialized. All flags zero, nid/zone > set to -1 (wild guess) and thus the crash? weird Yes that made me scratch my head as well. > >> I do wonder what hosts pfn_to_page(PHYS_PFN(0x6060000)) - is it actually > >> part of the actual altmap (i.e. > 0x6060000) or maybe even self-hosted? > > > > I am not really familiar with the pmem so I would need more assistance > > here. I've tried this (shot into the dark): > > crash> struct page.pgmap fffff8c600181800 > > pgmap = 0xfffff8c600181808 > > That's weird. If the memmap is at fffff8c600181800, why should the pgmap > be at an offset of 8 bytes from there. The "pgmap" field is actually at > an offset of 8 bytes within the memmap ... I haven't noticed this is an offset into struct page. This is indeed weird because the structure is much larger than struct page. But maybe it reuses storage of several struct pages in a row. Or maybe it is not pgmap but something else that shares the offset in the structure. -- Michal Hocko SUSE Labs
