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b=SIJ32kx6hB/dfXmQ8uJWAnyINL1xW1WydcdbZai8zq5LaGsbkWnkPIkZA208HscIza 677q0BKhryFlr3Q4Atyxj5nMBlGvyuIrwu64Az77+ZVXetwzaUQpj8fxwJCj/hJ20SuP cyVXF0fWQVRa6Hdv/TOjX+YEACQZnnNj+ksNREsqkcEJvraBkrzsJ3gJMMz62WJdcl5W bOQL26oDBTYMEKjtc3MnEYgv2jJ2HH1noS7dApZf2Ix344o27P7n6dOl6OLtNoJOoq/u vdp2njE/HugwALn6aKR1/PHODBooF/XxBHusMW2RTG+4QsSPBxvgKkT8VwChn6RUBh/F u17Q== X-Forwarded-Encrypted: i=1; AHgh+RpAD+2JgIFpUSNdpOWasltp3+QTFj1diSbQy3AtKU3MFiYSfQ1CgRjK774tzIJ5KVFb5E3cF13IeA==@kvack.org X-Gm-Message-State: AOJu0YzCRfWAGodSIU0pCUlErnXp357FMt3u4MEc2nXerjUjwh6mldpC VSFmI605QwEYB5V2ooYJ2qZN/e20MnW3trGl8KXY0nvX5PTkzsQkDyTxmCtFs7H1erXnWtDw57v wU14LhA== X-Received: from plbje14.prod.google.com ([2002:a17:903:264e:b0:2ca:eea9:9845]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:d488:b0:2d1:1a18:4d0a with SMTP id d9443c01a7336-2d3177a2163mr42800725ad.9.1786459715153; 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-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: 8bsq6tkzyhz5f1ajc4usqkezukbdzgji X-Rspamd-Queue-Id: 93F2D18000C X-HE-Tag: 1786459716-583768 X-HE-Meta: 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 OiaQafna 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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