On 17/11/2025 19:39, Peter Xu wrote:
On Mon, Nov 17, 2025 at 05:55:46PM +0000, Nikita Kalyazin wrote:
In our use case, Firecracker snapshot-restore using UFFD [1], we will use
UFFD minor/continue to respond to guest_memfd faults in user mappings
primarily due to VMM accesses that are required for PV (virtio) device
emulation and also KVM accesses when decoding MMIO operations on x86.
I'm curious if firecracker plans to support live snapshot save. When with
something like ioctls_supported flags, guest-memfd can declare support for
wr-protect support easily too, and synchronous userfaultfd wr-protect traps
will be an efficient way to do live save.
I'm guessing it's not an immediate demand now or it would have been asked
already supporting both MINOR and WP, but I just want to raise this
question. Qemu already supports live snapshot save, so it'll always be
good gmem can also support wp at some point, but it can be done later too.
No, live snapshots haven't been on our plan so far.
Thanks,
--
Peter Xu
