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 5A940221577; Sun, 30 Nov 2025 11:18:21 +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=1764501502; cv=none; b=qb1DlisCfWIamMtvdcWn88MvU2d0n5bp4nFfTa/6+/4k3tc4xoKkahW1+/Uq0E1tKB4TGJ3eEHiU3lRyv5S+8/nHzeJlSD6AtnP9rWPAB7PaydkocoVK0Vwk99VkqTEm5weRvwaitNBSQu0BwbDYdL1SxPyBGxBwPd6hQ17IegU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764501502; c=relaxed/simple; bh=QWyCUWNr5EiAGbEinbC1SqyvrF+pTj5s8nlr0+kSaV4=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=ZzCYaf4ASxhGtVcwktikTDDGAEOUY5Toal+1qmbmJDf8cNAySTgipffrzBvWPFlwCj33Q3ZmpQvpPDieJKUPcKDhrSm3dBIx0VhlrgUf6AtmrUgBnEruXKR2pyWsZEumhuImafoqD9U7ldj9DvKcIbVmjhzl8TcDZ33IvdLh5bI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XUtziVFw; 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="XUtziVFw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BA9E7C4CEF8; Sun, 30 Nov 2025 11:18:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1764501500; bh=QWyCUWNr5EiAGbEinbC1SqyvrF+pTj5s8nlr0+kSaV4=; h=From:To:Cc:Subject:Date:From; b=XUtziVFwxT+NlKvaS6WSYT+hiz0mrSRU2i7WVNjkPJridMQi1gJVaxfwESV5hKMLG BN3/0ZxZ/2DXLu6KtyIAMR3OGP+BuHSB7mPzKRRbzKyPqJR8YmW7n/weFmExIqYmtd 7S3JsaPSzIUgMK9FlfeSl9MJQo32lLw65KrX4tiLtUyULE/RclDDkSu7WAu6Tv55J3 gf46siqJ5aWDVA7l8SrR6snvp0GwbHKUcRBMPamwN8p8iGNLcKkG/4XQ1p0ZejStcH jf9uLE+kQcOwTjd9m8m1xzWcw4fqekafIhmzyolIu/YVxYX02l2rPQaNJa9U1vNIoc pL0mfDDnUxd0A== 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 v3 0/5] mm, kvm: add guest_memfd support for uffd minor faults Date: Sun, 30 Nov 2025 13:18:07 +0200 Message-ID: <20251130111812.699259-1-rppt@kernel.org> X-Mailer: git-send-email 2.51.0 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_folio_noalloc() 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. v3 changes: * rename ->get_folio() to ->get_folio_noalloc() * fix build errors reported by kbuild * pull handling of UFFD_MINOR out of hotpath in __do_fault() * update guest_memfs changes so its ->fault() and ->get_folio_noalloc() follow the same semantics as shmem and hugetlb. * s/MISSING/MINOR/g in changelogs * added review tags v2: https://lore.kernel.org/all/20251125183840.2368510-1-rppt@kernel.org * 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 | 5 +- mm/shmem.c | 20 +++- mm/userfaultfd.c | 80 ++++++++++++--- .../testing/selftests/kvm/guest_memfd_test.c | 97 +++++++++++++++++++ virt/kvm/guest_memfd.c | 33 ++++++- 8 files changed, 236 insertions(+), 54 deletions(-) base-commit: ac3fd01e4c1efce8f2c054cdeb2ddd2fc0fb150d -- 2.51.0