Re: [PATCH 3/4] KVM: x86/mmu: Add automatic prefaulting/prefetching for TDP MMU faults

[Marangoni, Marco]

On Fri, Oct 30, 2026, Sean Christopherson wrote:
> Oh, that's easy enough to "fix", the only question is whether or not that would
> be a net positive.

The only patterns for UFFD we've seen in Firecracker (both internally and externally) is to use fixed chunks on `UFFD_COPY`. There's some variability in the chunk size, we've seen it range from 512kiB to 4MiB, however it's always fixed.
So I agree, in this scenario, the approach of stopping at the first miss works and is not an issue when the prefault window is smaller or equal to the UFFD chunk size.