On Tue, Aug 27, 2024 at 03:36:07PM -0700, Jiaqi Yan wrote: > Hi Peter, Hi, Jiaqi, > I am curious if there is any work needed for unmap_mapping_range? If a > driver hugely remap_pfn_range()ed at 1G granularity, can the driver > unmap at PAGE_SIZE granularity? For example, when handling a PFN is Yes it can, but it'll invoke the split_huge_pud() which default routes to removal of the whole pud right now (currently only covers either DAX mappings or huge pfnmaps; it won't for anonymous if it comes, for example). In that case it'll rely on the driver providing proper fault() / huge_fault() to refault things back with smaller sizes later when accessed again. > poisoned in the 1G mapping, it would be great if the mapping can be > splitted to 2M mappings + 4k mappings, so only the single poisoned PFN > is lost. (Pretty much like the past proposal* to use HGM** to improve > hugetlb's memory failure handling). Note that we're only talking about MMIO mappings here, in which case the PFN doesn't even have a struct page, so the whole poison idea shouldn't apply, afaiu. Thanks, -- Peter Xu
