kernel/liveupdate/Kconfig | 16 +++++++++++++++- mm/Makefile | 2 +- tools/testing/selftests/liveupdate/config | 1 + 3 files changed, 17 insertions(+), 2 deletions(-)
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.
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
---
Changes v2:
- Updated testing config
- Added review-by
kernel/liveupdate/Kconfig | 16 +++++++++++++++-
mm/Makefile | 2 +-
tools/testing/selftests/liveupdate/config | 1 +
3 files changed, 17 insertions(+), 2 deletions(-)
diff --git a/kernel/liveupdate/Kconfig b/kernel/liveupdate/Kconfig
index d2aeaf13c3ac..9a1a8cdcf16c 100644
--- a/kernel/liveupdate/Kconfig
+++ b/kernel/liveupdate/Kconfig
@@ -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 +72,19 @@ 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
+ 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
diff --git a/mm/Makefile b/mm/Makefile
index 9175f8cc6565..798f04233d71 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -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
diff --git a/tools/testing/selftests/liveupdate/config b/tools/testing/selftests/liveupdate/config
index 91d03f9a6a39..1bfc708041bd 100644
--- a/tools/testing/selftests/liveupdate/config
+++ b/tools/testing/selftests/liveupdate/config
@@ -5,6 +5,7 @@ CONFIG_KEXEC_HANDOVER_ENABLE_DEFAULT=y
CONFIG_KEXEC_HANDOVER_DEBUGFS=y
CONFIG_KEXEC_HANDOVER_DEBUG=y
CONFIG_LIVEUPDATE=y
+CONFIG_LIVEUPDATE_MEMFD=y
CONFIG_LIVEUPDATE_TEST=y
CONFIG_MEMFD_CREATE=y
CONFIG_TMPFS=y
--
2.52.0.351.gbe84eed79e-googOn Tue, Dec 30, 2025 at 09:53:21AM -0500, Pasha Tatashin wrote: > 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. > > Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com> > Reviewed-by: Pratyush Yadav <pratyush@kernel.org> > --- > Changes v2: > - Updated testing config > - Added review-by > > kernel/liveupdate/Kconfig | 16 +++++++++++++++- > mm/Makefile | 2 +- > tools/testing/selftests/liveupdate/config | 1 + > 3 files changed, 17 insertions(+), 2 deletions(-) > > diff --git a/kernel/liveupdate/Kconfig b/kernel/liveupdate/Kconfig > index d2aeaf13c3ac..9a1a8cdcf16c 100644 > --- a/kernel/liveupdate/Kconfig > +++ b/kernel/liveupdate/Kconfig > @@ -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 +72,19 @@ 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 Maybe also 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 > diff --git a/mm/Makefile b/mm/Makefile > index 9175f8cc6565..798f04233d71 100644 > --- a/mm/Makefile > +++ b/mm/Makefile > @@ -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 > diff --git a/tools/testing/selftests/liveupdate/config b/tools/testing/selftests/liveupdate/config > index 91d03f9a6a39..1bfc708041bd 100644 > --- a/tools/testing/selftests/liveupdate/config > +++ b/tools/testing/selftests/liveupdate/config > @@ -5,6 +5,7 @@ CONFIG_KEXEC_HANDOVER_ENABLE_DEFAULT=y > CONFIG_KEXEC_HANDOVER_DEBUGFS=y > CONFIG_KEXEC_HANDOVER_DEBUG=y > CONFIG_LIVEUPDATE=y > +CONFIG_LIVEUPDATE_MEMFD=y then this is not needed :) > CONFIG_LIVEUPDATE_TEST=y > CONFIG_MEMFD_CREATE=y > CONFIG_TMPFS=y > -- > 2.52.0.351.gbe84eed79e-goog > -- Sincerely yours, Mike.
On Tue, Dec 30, 2025 at 10:30 AM Mike Rapoport <rppt@kernel.org> wrote: > > On Tue, Dec 30, 2025 at 09:53:21AM -0500, Pasha Tatashin wrote: > > 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. > > > > Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com> > > Reviewed-by: Pratyush Yadav <pratyush@kernel.org> > > --- > > Changes v2: > > - Updated testing config > > - Added review-by > > > > kernel/liveupdate/Kconfig | 16 +++++++++++++++- > > mm/Makefile | 2 +- > > tools/testing/selftests/liveupdate/config | 1 + > > 3 files changed, 17 insertions(+), 2 deletions(-) > > > > diff --git a/kernel/liveupdate/Kconfig b/kernel/liveupdate/Kconfig > > index d2aeaf13c3ac..9a1a8cdcf16c 100644 > > --- a/kernel/liveupdate/Kconfig > > +++ b/kernel/liveupdate/Kconfig > > @@ -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 +72,19 @@ 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 > > Maybe also > > default LIVEUPDATE Yeah, I like this idea, let me make the change, and send v3. Pasha
© 2016 - 2026 Red Hat, Inc.