[PATCH v3 0/2] kho: add support for preserving vmalloc allocations

Mike Rapoport
2025-09-08T10:35:42Z

From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>

Hi,

Following the discussion about preservation of memfd with LUO [1] these
patches add support for preserving vmalloc allocations.

Any KHO uses case presumes that there's a data structure that lists
physical addresses of preserved folios (and potentially some additional
metadata). Allowing vmalloc preservations with KHO allows scalable
preservation of such data structures.

For instance, instead of allocating array describing preserved folios in
the fdt, memfd preservation can use vmalloc:

preserved_folios = vmalloc_array(nr_folios, sizeof(*preserved_folios));
memfd_luo_preserve_folios(preserved_folios, folios, nr_folios);
kho_preserve_vmalloc(preserved_folios, &folios_info);

[1] https://lore.kernel.org/all/20250807014442.3829950-30-pasha.tatashin@soleen.com

v3 changes:
* rebase on mm-unstable

v2: https://lore.kernel.org/all/20250905131302.3595582-1-rppt@kernel.org
* support preservation of vmalloc backed by large pages
* add check for supported vmalloc flags and preserve the flags to be
able to identify incompatible preservations
* don't use kho_preserve_phys()
* add kernel-doc

v1: https://lore.kernel.org/all/20250903063018.3346652-1-rppt@kernel.org

Mike Rapoport (Microsoft) (2):
kho: add support for preserving vmalloc allocations
lib/test_kho: use kho_preserve_vmalloc instead of storing addresses in fdt

include/linux/kexec_handover.h | 12 ++
kernel/kexec_handover.c | 200 +++++++++++++++++++++++++++++++++
lib/test_kho.c | 41 +++++--
3 files changed, 241 insertions(+), 12 deletions(-)

base-commit: b024763926d2726978dff6588b81877d000159c1
--
2.50.1