On Mon, 1 Jun 2026, Pasha Tatashin wrote:
On 05-31 20:10, Mike Rapoport wrote:
- A freeze mechanism to lock the tree before serializing for kexec
(patch 13).
There were a lot of effort to make KHO stateless and drop the requirement
for finalization/freeze.
Yes, using KHO directly here is incorrect. The state machine is provided
by LUO, so we should use LUO here. MSHV should provide a file that
userspace adds to LUO, and all state machine management would be the
same as for all other clients participating in LU.
The thing is, there is no file handle to rely on. Even once partitions are
all removed, Hyper-V might hang onto pages (and won't return them even if
asked). However, these pages very much must be excluded from Linux
post-kexec, or the system will crash. We cannot rely on UM to ensure
integrity of memory management.
Contrast that to standard LUO use: If you drop individual file handles, or
even skip the LUO phase entirely, the worst that will happen is that the
objects will be gone post-kexec. The MM itself will still be consistent.
For MSHV & page donation, this is different.
(And yes, partition preservation will very much tie into LUO)
Best,
Jork
