Re: [PATCH V2] memory: flat section iterator

[Steven Sistare <steven.sistare@oracle.com>]

On 2/7/2023 3:10 PM, Peter Xu wrote:
> On Tue, Feb 07, 2023 at 11:03:29AM -0800, Steve Sistare wrote:
>> Add an iterator over the sections of a flattened address space.
>> This will be needed by cpr to issue vfio ioctl's on the same memory
>> ranges that are already programmed.
> 
> Should this better be proposed with the context of using it?  Or I don't
> know how to justify this new interface is needed.
> 
> For example, any explanations on why memory region listeners cannot work?

For context, the new interfaces is used in the patch
  "vfio-pci: recover from unmap-all-vaddr failure"
in the original live update series:
  https://lore.kernel.org/qemu-devel/1658851843-236870-1-git-send-email-steven.sistare@oracle.com/

More succinctly, the memory region listeners already ran, and the vfio 
callbacks created vfio memory regions.  Now we want to perform live update,
and are in steady state, so no listeners are being called.  We need the
flat section iterator to reproduce the same addresses and extents that were
produced by the listeners, to make a state change on each distinct vfio
memory region.

- Steve