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b=oWL/xvv0Ecw0+byyi+FYm+YqgpJUQd7rkxhyEU+OqTnezJNJmQTYOXllz0ZfQXurP HSOb6vFsiHAP6Z2O2N6gcii1eZrWM9e3R7/NPlp2GA752q542z8kFJoOvG/YPzqlqD iKYKdMfNv8Qk+Z1H+OZTtbTtg4gm5CTl6xxybmYolLtW5+KHj1snAKwa846Rt4HPlT fWhuMQ78kHGtTKaYABYWhRNt8+R7IUYV92RMOdn/oqFED4BHhaNkczEQGw1fMw7X2E SYsJoIFjsEZuOmdPYwA/r5KYajK4hPeksolQMdgY83/MMf9mHkcMmqnLgvwtoA6Vy4 icWl+pRjNvuXA== Message-ID: <3cdf9ac0-b77c-4624-ad8e-68c10af648ac@kernel.org> Date: Fri, 21 Aug 2026 15:39:04 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 0/9] KVM: guest_memfd: folio migration for non-confidential VMs To: "Garg, Shivank" , "Gupta, Pankaj" , "Sampat, Pratik Rajesh" , "nikita.kalyazin@linux.dev" , "ying.huang@linux.alibaba.com" , "patrick.roy@linux.dev" , "joshua.hahnjy@gmail.com" , "pbonzini@redhat.com" , "jmattson@google.com" , "hannes@cmpxchg.org" , "jack@suse.cz" , "tglx@kernel.org" , "Dadhania, Nikunj" , "Roth, Michael" , "corbet@lwn.net" , "mhocko@suse.com" , "gourry@gourry.net" , "iweiny@kernel.org" , "chao.p.peng@linux.intel.com" , "byungchul@sk.com" , "x86@kernel.org" , "bp@alien8.de" , "ricarkol@google.com" , "vannapurve@google.com" , "shuah@kernel.org" , "seanjc@google.com" , "jackmanb@google.com" , "Kalra, Ashish" , "willy@infradead.org" , "surenb@google.com" , "pshier@google.com" , "matthew.brost@intel.com" , "fuad.tabba@linux.dev" , "skhan@linuxfoundation.org" , "hpa@zytor.com" , "mingo@redhat.com" , "rakie.kim@sk.com" , "ackerleytng@google.com" , "apopple@nvidia.com" , "ziy@nvidia.com" , "vbabka@kernel.org" , "akpm@linux-foundation.org" , "dave.hansen@linux.intel.com" Cc: "linux-kselftest@vger.kernel.org" , "sashiko-bot@kernel.org" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "linux-doc@vger.kernel.org" , "kvm@vger.kernel.org" , "linux-coco@lists.linux.dev" , "linux-fsdevel@vger.kernel.org" References: <20260805-shivank-gmem-migrate-v3-0-00d8bdec4e1d@amd.com> <0a02a6c4f0ee50ca596c4a2673b2ae6c80d4569b.camel@amd.com> 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-Stat-Signature: iw41cdfabhqojmzff5yaei8w56efmrpj X-Rspamd-Queue-Id: B03C610000A X-Rspamd-Server: rspam03 X-Rspam-User: X-HE-Tag: 1787319561-505573 X-HE-Meta: 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 rjQVsUWP 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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 8/21/26 14:34, Garg, Shivank wrote: > On Wed, 2026-08-05 at 06:40 +0000, Shivank Garg wrote: >> guest_memfd folios are currently always marked unmovable, so the kernel cannot >> perform memory compaction, offlining, etc. This is unavoidable for >> confidential VMs (SEV-SNP, TDX), since memory is encrypted and copying it >> needs firmware assistance. However, for non-confidential VMs (like >> Firecracker), we can migrate the folios. >> >> This series enables folio migration for non-confidential guest_memfd and >> also lays the groundwork for migrating confidential guest_memfd later. >> Once firmware-assisted copying support is available, those VMs can be >> made movable, the confidential folio content can be copied separately, >> and the destination folio marked with FOLIO_CONTENT_COPIED[4] so >> __migrate_folio() skips the host-side folio_mc_copy(). >> >> Testing >> ------- >> Host: 7.2-rc6+(c21bb419386) + this, AMD EPYC ZEN 3, 2 NUMA nodes >> >> - KVM selftest: allocate folios on node 0, migrate them to node 1 and >> back and verify resulting NUMA node and the folio contents at each >> step. >> >> - Firecracker [1]: booted a microVM backed by guest_memfd. While the >> guest was running, forced host-side migration of its folios via >> migratepages(8) and explicit move_pages(2) of guest_memfd >> pages. Verify with /proc/firecracker_pid/numa_maps. >> >> Notes >> ----- >> - Sashiko pointed out a pre-existing ABBA deadlock between >> kvm_gmem_error_folio() and truncation. It's being addressed separately >> by Hao Zhang. [2][3] >> >> [1] https://github.com/firecracker-microvm/firecracker/tree/feature/secret-hiding >> In builder.rs, add GUEST_MEMFD_FLAG_MIGRATABLE to bit-2 and pass it instead >> of GUEST_MEMFD_FLAG_NO_DIRECT_MAP to vm.create_guest_memfd(). >> [2] https://lore.kernel.org/all/ambEdSPjerZIVN0b@192.168.1.215/ >> [3] https://sashiko.dev/#/patchset/20260611-shivank-gmem-migrate-v1-0-2d266bfc6f95%40amd.com >> [4] https://lore.kernel.org/all/20260630-shivank-batch-migrate-offload-v6-1-da95d7e8b8a2@amd.com >> >> Signed-off-by: Shivank Garg >> --- >> Changes in v3: >> - Fix unbalanced mmu_invalidate_in_progress count unbinding dying guest_memfd. (Sashiko) >> - Fix maxnode handling in xapic_ipi_test selftest. >> - Add GUEST_MEMFD_FLAG_MIGRATABLE documentation >> - Replace open-coded sizeof() * 8 calculation with BITS_PER_TYPE() >> - Add get_numa_mem_nodes() and use MPOL_F_MEMS_ALLOWED for allowed NUMA ndoes >> instead of hardcoded NUMA node IDs. (Sashiko) >> - Extend migration selftest to verify rejection without MIGRATABLE flag and >> move repeated checks into common helpers. >> - Drop RFC tag. >> - Link to v2: https://lore.kernel.org/r/20260728-shivank-gmem-migrate-v2-0-269ac1f84e2b@amd.com >> >> Changes in v2: >> - Make folio migration opt-in through GUEST_MEMFD_FLAG_MIGRATABLE, >> preserving unmovable behavior if userspace don't explictly ask. (Alexandru, David, Sean) >> - Add kvm_arch_supports_gmem_migration() so arch can control whether >> GUEST_MEMFD_FLAG_MIGRATABLE is advertised. >> - Allocate movable folios with GFP_HIGHUSER_MOVABLE. (David) >> - Keep guest_memfd unevictable. (David, Sashiko, Sean) >> - Split migrate_folio() implementation and enablement as separate patches. >> - Update selftest with new flag. >> - Link to v1: https://lore.kernel.org/r/20260611-shivank-gmem-migrate-v1-0-2d266bfc6f95@amd.com >> >> --- >> Shivank Garg (9): >> KVM: guest_memfd: take the invalidate lock when unbinding a dying file >> mm: split AS_UNMOVABLE back out of AS_INACCESSIBLE >> KVM: guest_memfd: implement folio migration for non-confidential VMs >> KVM: guest_memfd: add GUEST_MEMFD_FLAG_MIGRATABLE >> KVM: selftests: fix maxnode arguments in xapic_ipi_test >> KVM: selftests: use BITS_PER_TYPE() for NUMA masks >> KVM: selftests: add get_numa_mem_nodes() >> KVM: selftests: use allowed NUMA nodes in guest_memfd_test >> KVM: selftests: exercise guest_memfd folio migration >> >> > > Should I spin the independent patches out of this series for next cycle? I'd say, yes :) -- Cheers, David