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Tue, 11 Aug 2026 07:48:35 -0700 (PDT) Date: Tue, 11 Aug 2026 07:48:34 -0700 In-Reply-To: <9huzqzk4zt3n.fsf@tarunix.c.googlers.com> Mime-Version: 1.0 References: <20260728121138.1103610-1-tarunsahu@google.com> <20260728121138.1103610-2-tarunsahu@google.com> <9huzqzk4zt3n.fsf@tarunix.c.googlers.com> Message-ID: Subject: Re: [PATCH v4 01/11] liveupdate: Add LIVEUPDATE_GUEST_MEMFD config option From: Sean Christopherson To: tarunsahu@google.com Cc: ackerleytng@google.com, fuad.tabba@linux.dev, Andrew Morton , dmatlack@google.com, Shuah Khan , Jonathan Corbet , david@redhat.com, Pasha Tatashin , Pratyush Yadav , sagis@google.com, Paolo Bonzini , Mike Rapoport , Alexander Graf , linux-kselftest@vger.kernel.org, andre.przywara@arm.com, michael.roth@amd.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, will@kernel.org, vannapurve@google.com, maz@kernel.org, fvdl@google.com, kvm@vger.kernel.org, oliver.upton@linux.dev, kvmarm@lists.linux.dev, alexandru.elisei@arm.com, skhawaja@google.com, aneesh.kumar@kernel.org, linux-doc@vger.kernel.org, David Hildenbrand , yan.y.zhao@intel.com, kexec@lists.infradead.org, suzuki.poulose@arm.com Content-Type: text/plain; charset="us-ascii" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260811_074837_869761_E1213759 X-CRM114-Status: GOOD ( 18.49 ) X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org On Tue, Aug 11, 2026, tarunsahu@google.com wrote: > Sean Christopherson writes: > > > On Tue, Jul 28, 2026, Tarun Sahu wrote: > >> Introduce the LIVEUPDATE_GUEST_MEMFD Kconfig option. This option > >> enables live update support for KVM guest_memfd files, enabling > >> guest_memfd-backed memory preservation across kernel upgrades. > >> > >> Currently this support only guest_memfd files that are full-shared > >> (INIT_SHARED and no support for private_mem). > > > > Why? Specifically, why do we need/want a separate Kconfig for guest_memfd > > liveupdate versus KVM liveupdate? I can _maybe_ see a KVM-wide Kconfig, but > > even that seems like a stretch given that (AFAIK) hypervisors are the one and > > only use-case for liveupdate. > > LIVEUPDATE is used in many subsystem. It is possible to enable > liveupdate and kvm without enabling KVM_GUEST_MEMFD. So GUEST_MEMFD > preservation must depend on CONFIG_LIVEUPDATE and KVM_GUEST_MEMFD both. > LIVEUPDATE_GUEST_MEMFD Kconfig is wrapper on both of them. It need not > to be visible in menu, So I can make it hidden. WDYT? > > Also, KVM VM_FILE preservation and GUEST_MEMFD preservation both depends > on LIVEUPDATE_GUEST_MEMFD in this patch series. [PATCH 05/11]* > Which is wrong. So I will update KVM VM_FILE preservation to depend only > on CONFIG_LIVEUPDATE. Or just handle it all in the makefile? E.g. diff --git virt/kvm/Makefile.kvm virt/kvm/Makefile.kvm index d047d4cf58c9..e6f098498795 100644 --- virt/kvm/Makefile.kvm +++ virt/kvm/Makefile.kvm @@ -13,3 +13,8 @@ kvm-$(CONFIG_HAVE_KVM_IRQ_ROUTING) += $(KVM)/irqchip.o kvm-$(CONFIG_HAVE_KVM_DIRTY_RING) += $(KVM)/dirty_ring.o kvm-$(CONFIG_HAVE_KVM_PFNCACHE) += $(KVM)/pfncache.o kvm-$(CONFIG_KVM_GUEST_MEMFD) += $(KVM)/guest_memfd.o + +ifdef CONFIG_LIVEUPDATE +kvm-y += $(KVM)/kvm_luo.o +kvm-$(CONFIG_KVM_GUEST_MEMFD) += $(KVM)/guest_memfd_luo.o +endif