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imf05.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=Wv97yqYT; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf05.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1781692488; b=AMjlRSj8neBB+QlA3p/dy0sSeoHAdaxPe3r09TGUWZ3F2kNs6hKwLMlr59LID6CTrR6AXh tHJPiclbKpD7aE7ijihQpBed2jTnWlhTU30dWmUy6szezUbBrbOdPFTyzC45lHolDryeFT O5y/fNPkvvyhyAGeI5ECCsJRCdFL0g8= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id B340160137; Wed, 17 Jun 2026 10:34:47 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 38FC81F000E9; Wed, 17 Jun 2026 10:34:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781692487; bh=mUzimGhtwXxeFlNbjp2T5cpsz2AsOPIbGLnMGM1e6Dk=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Wv97yqYTUmHJUFnZj5sV6+KfbOH9WCS97aAe2ipipFgYFnAgIyBaKA0DCVPWhme8b jBXKmFR2LjzO+WhSOm9S4yVMbmlCGSH11yqqO0mq9Xr+BMQwf85wyzev4hqlx7sAUT TP75DRBIfR2q7apcjUstwzSBStuIhrXIKy0StOYafxpFp1VHhyvgwcppG1/+ui/4da DESJJGo+QdHVu+ZYi2jSI9lSUgtYxh3qp8sgvNI53EqqofZTgpeK2jKBhZFfFk8Wf3 TqJyGELBLbKO32SIHiP5JHb5yBTFjIcK1lUfKpyDqSi0Ae97MquHzGkCTY7bgu/xsK W2A4DwTyVd02g== Message-ID: <9ebadac0-0ec2-4ebc-8193-1a289574c0a9@kernel.org> Date: Wed, 17 Jun 2026 12:34:38 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC 0/3] KVM: guest_memfd: folio migration for non-confidential VMs To: Ackerley Tng , Sean Christopherson , Alexandru Elisei Cc: Shivank Garg , "Matthew Wilcox (Oracle)" , Jan Kara , Andrew Morton , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Paolo Bonzini , Shuah Khan , Chao Peng , Nikunj A Dadhania , Ira Weiny , Michael Roth , Pankaj Gupta , Fuad Tabba , Vishal Annapurve , Nikita Kalyazin , Patrick Roy , Pratik Sampat , Ashish Kalra , linux-fsdevel@vger.kernel.org, linux-coco@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org References: <20260611-shivank-gmem-migrate-v1-0-2d266bfc6f95@amd.com> <1e77f24d-315a-4f68-a109-2f4520343c0c@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 6A3EB10000E X-Rspam-User: X-Stat-Signature: zgz64bis6n9rmg68ru1p3z5mzkpwabdq X-Rspamd-Server: rspam09 X-HE-Tag: 1781692488-20765 X-HE-Meta: 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 Wf01SHPp 3aCUosRY8+ww0y1MYBgvbvn70sPOtX4U1mPHlbrAoXpg7I+WznpBxAdVTWa51B/Cvj00euQu3IkTsgMmXvxwXSDgddoauZJI+J5ssgo+ovdOH+zMlTNM7UXUqbmJ/EzXYy04vaqunVCpjXfNnX9KHyGM5g4tl7gTx/YjEu7AgEAwdem6iYvCHZ6IoLqqUu2YlTnvgj5BLkgpB8QbMgmCwozgO+8SyY8JR5ovDrQoohdEguf5ltizNMMcqi346mBaoMYEJhq3nsJc5ha+REPuitGK6+0Cg9NbNz5LdEW8cM/EKFtkb0ZyJ+BgGBYlIYepj/nZGn/xrvl6jjOtrkAk8ZLbGqcB/X12mQGc5WHtxE1fmmvHEixtF5PrMTjs1ONhawWFLtyZ9c8dk9LuW9Qc1y5m1qg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 6/16/26 20:09, Ackerley Tng wrote: > "David Hildenbrand (Arm)" writes: > >> On 6/15/26 19:39, Sean Christopherson wrote: >>> >>> +1000. It's not just "nice to have", it's a core design principle of guest_memfd. >> >> Right, and I raised in the guest_memfd call also the rough idea of Alexandru's >> use case of having non-movable guest_memfd pages such that we can support use >> cases where we can hopefully guarantee that a stage-2 mapping will not just >> randomly go away. >> >>> > > More concretely, are y'all pointing towards a > GUEST_MEMFD_FLAG_MIGRATABLE, which will set .migrate = > kvm_gmem_migrate_folio, and for now, error out for CoCo VMs? > >>> >>> For the purposes of this discussion, we should separate the physical act of >>> migrating pages from the features that trigger migration. As I said in last week's >>> guest-memfd call, I am a-ok with supporting page migration as a mechanism, but I >>> am dead set against supporting NUMA balancing, KSM, LRU-based swap/reclaim, and >>> anything else that goes against the goal of guest-first memory. >> >> Right. Page migration for supporting ZONE_MOVABLE/CMA, compaction, memory >> offlining, virtio-mem and possibly some collapse mechanism if we were to support >> THP of some sorts in guest_memfd would are all reasonable. >> > > Background question: how would virtio-mem use migration in the host/guest_memfd? Good question! As long as there is no nested-virt support (and virtio-mem support for coco still being in the making) that wouldn't apply, only ordinary memory hot(un)plug (incl CXL). -- Cheers, David