On Thu, Sep 04, 2025, James Houghton wrote: > On Thu, Sep 4, 2025 at 9:43 AM Nikita Kalyazin <kalyazin@xxxxxxxxxx> wrote: > > Are there any blockers for merging this series? We would like to use > > the functionality in Firecracker for restoring guest_memfd-backed VMs > > from snapshots via UFFD [1]. [2] is a Firecracker feature branch that > > builds on top of KVM userfault, along with direct map removal [3], write > > syscall [4] and UFFD support [5] in guest_memfd (currently in discussion > > with MM at [6]) series. > > Glad to hear that you need this series. :) Likewise (though I had slightly-advanced warning from Patrick that Firecracker wants KVM Userfault). The main reason I haven't pushed harder on this series is that I didn't think anyone wanted to use it within the next ~year. > I am on the hook to get some QEMU patches to demonstrate that KVM > Userfault can work well with it. I'll try to get that done ASAP now > that you've expressed interest. The firecracker patches are a nice > demonstration that this could work too... (I wish the VMM I work on > was open-source). > > I think the current "blocker" is the kvm_page_fault stuff[*]; KVM > Userfault will be the first user of this API. I'll review that series > in the next few days. I'm pretty sure Sean doesn't have any conceptual > issues with KVM Userfault as implemented in this series. Yep, Oliver and I (and anyone else that has an opinion) just need to align on the interface for arch-neutral code. I think that's mostly on me to spin a v2, and maybe to show how it all looks when integrated with the userfault stuff.
