On Mon, 2020-08-03 at 10:28 -0500, Eric W. Biederman wrote: [...] > What is wrong with live migration between one qemu process and > another qemu process on the same machine not work for this use case? > > Just reusing live migration would seem to be the simplest path of > all, as the code is already implemented. Further if something goes > wrong with the live migration you can fallback to the existing > process. With exec there is no fallback if the new version does not > properly support the handoff protocol of the old version. Actually, could I ask this another way: the other patch set you sent to the KVM list was to snapshot the VM to a PKRAM capsule preserved across kexec using zero copy for extremely fast save/restore. The original idea was to use this as part of a CRIU based snapshot, kexec to new system, restore. However, why can't you do a local snapshot, restart qemu, restore using the PKRAM capsule to achieve exactly the same as MADV_DOEXEC does but using a system that's easy to reason about? It may be slightly slower, but I think we're still talking milliseconds. James
