From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0ED442D97A4; Tue, 25 Nov 2025 18:38:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764095930; cv=none; b=MnScnTAW96rXkXQnUhRztuNFT9ZEHUKxPl/CfzWAypOmxK5Uzh9ugU46PN/H7f+RFb3uTiwUND8GgXVI3t0+GmRkuFuhDG5mGJUCxiu5ut79ikRKLwcfBtY5mKreYq2/hZCpPOCspcSPERMnVPzGW+UX3rkHy3ZMtTvqaESzSYE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764095930; c=relaxed/simple; bh=rWudt7B1tB5QYi97/yII2g+5R+2VjlqdXJtZwSgAGQc=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=eq8GyRtoW73gKNyJz4NjlRI/6DzB5JgjYZI66ivbTqMPXtvDa+XoVD7oCwKHd39y3DPR86vRtZICN+FQbS8fIrnFPrp4yu+DHXE4LEJF2d/ZX1NboTFLppWqjsZS8b6D4B2I9zzum9lHWI2cudZ0b25IJnTH4uoMNOMF9qHPWuY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=eFbfUd4W; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="eFbfUd4W" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 75691C4CEF1; Tue, 25 Nov 2025 18:38:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1764095929; bh=rWudt7B1tB5QYi97/yII2g+5R+2VjlqdXJtZwSgAGQc=; h=From:To:Cc:Subject:Date:From; b=eFbfUd4W8t5SYla89AonVE6qfu9YF5+7CRm35LEhJB4Ikan/rfMCWcR7mhNLJeBDN 0C/ul7ZztYy+gyI2m2WGHvgGtWSUlxyGEXnR11maVQjbyVWPK63NuqZ/qCel8GTR3L lQsCIRYMVVDYF37ETz7+Znh4pQq/oNO4n8xcHeF4h17fvJk+DWbeO4x2cr/YeFzjIz JJn/f+MbzgDHOPJ+4PLtMm/c0sCSfW8dCXiKT83+1T3jX7FF0RHN2aoOxz3/LSAmCY eAd82I2/jODtfeYzxfIqf6qd8rINpJuRO9UZPXKjG7MQomeUyiZMZIWMxvNRp27/fX nEIbnvbJ7TE6w== From: Mike Rapoport To: linux-mm@kvack.org Cc: Andrea Arcangeli , Andrew Morton , Axel Rasmussen , Baolin Wang , David Hildenbrand , Hugh Dickins , James Houghton , "Liam R. 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 v2 0/5] mm, kvm: add guest_memfd support for uffd minor faults Date: Tue, 25 Nov 2025 20:38:35 +0200 Message-ID: <20251125183840.2368510-1-rppt@kernel.org> X-Mailer: git-send-email 2.50.1 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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: * rename ->get_shared_folio() to ->get_folio() * hardwire VM_FAULF_UFFD_MINOR to 0 when CONFIG_USERFAULTFD=n v1: https://patch.msgid.link/20251123102707.559422-1-rppt@kernel.org * 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 rfc: https://patch.msgid.link/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 | 10 +- include/linux/userfaultfd_k.h | 36 +----- mm/memory.c | 2 + mm/shmem.c | 20 +++- mm/userfaultfd.c | 80 +++++++++++--- .../testing/selftests/kvm/guest_memfd_test.c | 103 ++++++++++++++++++ virt/kvm/guest_memfd.c | 28 +++++ 8 files changed, 236 insertions(+), 52 deletions(-) base-commit: 6a23ae0a96a600d1d12557add110e0bb6e32730c -- 2.50.1