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liveupdate: separate memfd support into LIVEUPDATE_MEMFD

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Decouple memfd preservation support from the core Live Update Orchestrator
configuration.

Previously, enabling CONFIG_LIVEUPDATE forced a dependency on CONFIG_SHMEM
and unconditionally compiled memfd_luo.o.  However, Live Update may be
used for purposes that do not require memfd-backed memory preservation.

Introduce CONFIG_LIVEUPDATE_MEMFD to gate memfd_luo.o.  This moves the
SHMEM and MEMFD_CREATE dependencies to the specific feature that needs
them, allowing the base LIVEUPDATE option to be selected independently of
shared memory support.

Link: https://lkml.kernel.org/r/20251230161402.1542099-1-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Pasha Tatashin 2025-12-30 11:14:02 -05:00 • committed by Andrew Morton
parent 1921044eeb
commit 998be0a4db
2 changed files with 17 additions and 2 deletions
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17
kernel/liveupdate/Kconfig
View file

@ -54,7 +54,6 @@ config KEXEC_HANDOVER_ENABLE_DEFAULT
config LIVEUPDATE
bool "Live Update Orchestrator"
depends on KEXEC_HANDOVER
depends on SHMEM
help
Enable the Live Update Orchestrator. Live Update is a mechanism,
typically based on kexec, that allows the kernel to be updated
@ -73,4 +72,20 @@ config LIVEUPDATE
If unsure, say N.
config LIVEUPDATE_MEMFD
bool "Live update support for memfd"
depends on LIVEUPDATE
depends on MEMFD_CREATE
depends on SHMEM
default LIVEUPDATE
help
Enable live update support for memfd regions. This allows preserving
memfd-backed memory across kernel live updates.
This can be used to back VM memory with memfds, allowing the guest
memory to persist, or for other user workloads needing to preserve
pages.
If unsure, say N.
endmenu

2
mm/Makefile
View file

@ -100,7 +100,7 @@ obj-$(CONFIG_NUMA) += memory-tiers.o
obj-$(CONFIG_DEVICE_MIGRATION) += migrate_device.o
obj-$(CONFIG_TRANSPARENT_HUGEPAGE) += huge_memory.o khugepaged.o
obj-$(CONFIG_PAGE_COUNTER) += page_counter.o
obj-$(CONFIG_LIVEUPDATE) += memfd_luo.o
obj-$(CONFIG_LIVEUPDATE_MEMFD) += memfd_luo.o
obj-$(CONFIG_MEMCG_V1) += memcontrol-v1.o
obj-$(CONFIG_MEMCG) += memcontrol.o vmpressure.o
ifdef CONFIG_SWAP