On Tue, Mar 09, 2021 at 01:11:04PM -0700, Alex Williamson wrote: > > It's just that the initial MMIO access delay would be spread to the 1st access > > of each mmio page access rather than using the previous pre-fault scheme. I > > think an userspace cares the delay enough should pre-fault all pages anyway, > > but just raise this up. Otherwise looks sane. > > Yep, this is a concern. Is it safe to have loops concurrently and fully > populating the same vma with vmf_insert_pfn()? AFAIU it's safe, and probably the (so far) best way for an userspace to quickly populate a huge chunk of mmap()ed region for either MMIO or RAM. Indeed from that pov vmf_insert_pfn() seems to be even more efficient on prefaulting since it can be threaded. Thanks, -- Peter Xu
