On Fri, Mar 14, 2025 at 05:12:35PM +0000, Nikita Kalyazin wrote: > Yes, I was thinking about MADV_POPULATE_WRITE as well, but AFAIK it isn't > available in guest_memfd, at least with direct map removed due to [1] being > updated in [2]: I see, so GUP is no-go. IIUC the userapp can also prefault by writing zeros in a loop after mmap(). Thanks, -- Peter Xu