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[34.85.221.182]) by smtp.gmail.com with ESMTPSA id 00721157ae682-78fb44f0e3csm127690847b3.28.2025.12.30.08.14.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 30 Dec 2025 08:14:06 -0800 (PST) From: Pasha Tatashin To: akpm@linux-foundation.org, pasha.tatashin@soleen.com, rppt@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, pratyush@kernel.org Subject: [PATCH v3] liveupdate: separate memfd support into LIVEUPDATE_MEMFD Date: Tue, 30 Dec 2025 11:14:02 -0500 Message-ID: <20251230161402.1542099-1-pasha.tatashin@soleen.com> X-Mailer: git-send-email 2.52.0.351.gbe84eed79e-goog Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 Reviewed-by: Pratyush Yadav Reviewed-by: Mike Rapoport (Microsoft) --- Changes v3 - Addressed Mike's suggestion: added default LIVEUPDATE, and removed config from selftests. kernel/liveupdate/Kconfig | 17 ++++++++++++++++- mm/Makefile | 2 +- 2 files changed, 17 insertions(+), 2 deletions(-) diff --git a/kernel/liveupdate/Kconfig b/kernel/liveupdate/Kconfig index d2aeaf13c3ac..1a8513f16ef7 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 +72,20 @@ config LIVEUPDATE =20 If unsure, say N. =20 +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 diff --git a/mm/Makefile b/mm/Makefile index 9175f8cc6565..798f04233d71 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -100,7 +100,7 @@ obj-$(CONFIG_NUMA) +=3D memory-tiers.o obj-$(CONFIG_DEVICE_MIGRATION) +=3D migrate_device.o obj-$(CONFIG_TRANSPARENT_HUGEPAGE) +=3D huge_memory.o khugepaged.o obj-$(CONFIG_PAGE_COUNTER) +=3D page_counter.o -obj-$(CONFIG_LIVEUPDATE) +=3D memfd_luo.o +obj-$(CONFIG_LIVEUPDATE_MEMFD) +=3D memfd_luo.o obj-$(CONFIG_MEMCG_V1) +=3D memcontrol-v1.o obj-$(CONFIG_MEMCG) +=3D memcontrol.o vmpressure.o ifdef CONFIG_SWAP --=20 2.52.0.351.gbe84eed79e-goog