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Howlett" , Lorenzo Stoakes , Michal Hocko , Mike Rapoport , Nikita Kalyazin , Paolo Bonzini , Peter Xu , Sean Christopherson , Shuah Khan , Suren Baghdasaryan , Vlastimil Babka , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH 0/5] mm, kvm: add guest_memfd support for uffd minor faults Date: Sun, 23 Nov 2025 12:27:02 +0200 Message-ID: <20251123102707.559422-1-rppt@kernel.org> X-Mailer: git-send-email 2.50.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: A502B14000E X-Stat-Signature: ydqnwqn78ydorcwowh66omkyoa9ttajf X-Rspam-User: X-HE-Tag: 1763893637-967540 X-HE-Meta: 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 XkhlUqDA Ytn1FxFjkTmApeYAC5H2vlEXlZqwEzDCss4AV3yugAXUIC9FZ4m/4HHY5hkp4zBxC1y/CgKG6AHEOeAvjMonYV/JRgdUgeR7RMzxr0n9Rzl0LqoqVT7FBBuBtC1wTkKu5IyDAos9gcNkCqapZ3HzKi5t0upQ+ReJXY1sZUFyRZKO7olIJS/PYS+OZ16t/jlKdybFkkgsTjyGlssQih4c1V/pTQIKzW6vVTGswGnTqVLToj6w0xUAG9SqxQb6Q/Cty9KKujS9xsJplKE2fnOe5Wxh3NQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: "Mike Rapoport (Microsoft)" Hi, These patches allow guest_memfd to notify userspace about minor page faults using userfaultfd and let userspace to resolve these page faults using UFFDIO_CONTINUE. To allow UFFDIO_CONTINUE outside of the core mm I added a get_shmem_folio() callback to vm_ops that allows an address space backing a VMA to return a folio that exists in it's page cache (patch 2) In order for guest_memfd to notify userspace about page faults, there is a new VM_FAULT_UFFD_MINOR that a ->fault() handler can return to inform the page fault handler that it needs to call handle_userfault() to complete the fault (patch 3). Patch 4 plumbs these new goodies into guest_memfd. This series is the minimal change I've been able to come up with to allow integration of guest_memfd with uffd and while refactoring uffd and making mfill_atomic() flow more linear would have been a nice improvement, it's way out of the scope of enabling uffd with guest_memfd. v2 changes: * Introduce VM_FAULF_UFFD_MINOR to avoid exporting handle_userfault() * Simplify vma_can_mfill_atomic() * Rename get_pagecache_folio() to get_shared_folio() and use inode instead of vma as its argument v1: https://lore.kernel.org/all/20251117114631.2029447-1-rppt@kernel.org Mike Rapoport (Microsoft) (4): userfaultfd: move vma_can_userfault out of line userfaultfd, shmem: use a VMA callback to handle UFFDIO_CONTINUE mm: introduce VM_FAULT_UFFD_MINOR fault reason guest_memfd: add support for userfaultfd minor mode Nikita Kalyazin (1): KVM: selftests: test userfaultfd minor for guest_memfd include/linux/mm.h | 9 ++ include/linux/mm_types.h | 3 + include/linux/userfaultfd_k.h | 36 +----- mm/memory.c | 2 + mm/shmem.c | 21 +++- mm/userfaultfd.c | 80 +++++++++++--- .../testing/selftests/kvm/guest_memfd_test.c | 103 ++++++++++++++++++ virt/kvm/guest_memfd.c | 29 +++++ 8 files changed, 232 insertions(+), 51 deletions(-) base-commit: 6a23ae0a96a600d1d12557add110e0bb6e32730c -- 2.50.1