On Tue, Mar 18, 2025 at 04:20:17PM +0800, Huan Yang wrote: > This prevents us from properly invoking vmap, which is why we have turned to using vmap_pfn instead. > > Even if a folio-based vmap is implemented, it still cannot handle mapping multiple folio ranges of physical > > memory to vmalloc regions. A range of folio is important, it maybe an offset in memfd, no need entire folio. > > So, I still consider vmap_pfn to be the optimal solution for this specific scenario. :) No, vmap_pfn is entirely for memory not backed by pages or folios, i.e. PCIe BARs and similar memory. This must not be mixed with proper folio backed memory. So you'll need a vmap for folios to support this use case. > >> historically backed by pages and now folios. > > So by HVO, it also not backed by pages, only contains folio head, each tail pfn's page struct go away. And a fully folios based vmap solves that problem.
