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AHgh+RoMtXZzgUzOxHMB78RRjLEOQ6s4mP76ZZlr9b3VdLS8uv3mDjbZLhBgJNvHFcdMzfuWkYA=@vger.kernel.org X-Gm-Message-State: AOJu0YymFMJF/S0UOTpxNi7q+YA/uUgw76FlowjGw/PwVVOavMRnRKyp dgKrkk+VPe9J3xnAli9pH5SRue5Wn+RK75sN3382fmikZBFkkgb4HbZlO+KMyCslcDsL+dNuqVQ aQRKxPg== X-Received: from pgcc9.prod.google.com ([2002:a63:1c09:0:b0:c9b:2759:d240]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a20:6f8a:b0:3c4:1916:9d46 with SMTP id adf61e73a8af0-3cc71f4a5famr9143644637.27.1786723487045; Fri, 14 Aug 2026 09:04:47 -0700 (PDT) Date: Fri, 14 Aug 2026 09:04:46 -0700 In-Reply-To: Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <487aa57c-72ad-453b-971d-ca24a8380429@arm.com> Message-ID: Subject: Re: [RFC PATCH 0/3] KVM: Dirty page logging for guest_memfd-only memslots From: Sean Christopherson To: Alexandru Elisei Cc: David Hildenbrand , Mark Rutland , pbonzini@redhat.com, kvm@vger.kernel.org, maz@kernel.org, oupton@kernel.org, joey.gouly@arm.com, seiden@linux.ibm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, fuad.tabba@linux.dev Content-Type: text/plain; charset="us-ascii" On Fri, Aug 14, 2026, Alexandru Elisei wrote: > On Fri, Aug 14, 2026 at 06:03:54AM -0700, Sean Christopherson wrote: > > > That would be in contrast to user space having to guess that page migration on > > > the current hardware with the current guest_memfd implementation does not > > > support page migration, to then disable exactly that. > > If guest_memfd picks up support for another feature that might lead to > memory being unmapped from stage 2 without userspace initiating it, would > you be ok with that feature being gated by another guest_memfd flag? Yes, absolutely. FWIW, if I get my way and reclaim is driven by userspace, then hopefully such a feature never comes along. But if guest_memfd does gain some feature that triggers invalidations, then yeah, at the very least it would need to have some knowledge of whether or not the associated VM supports said feature. > I get the feeling we're all on the same page, that guest_memfd will support > a mode where memory isn't unmapped from stage 2, and right now the > discussion is more about how that will be implemented. Ya.