linux-kernel - [PATCH 0/5] mm, kvm: add guest_memfd support for uffd minor faults

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20251123102707.559422-1-rppt@kernel.org>
Date: Sun, 23 Nov 2025 12:27:02 +0200
From: Mike Rapoport <rppt@...nel.org>
To: linux-mm@...ck.org
Cc: Andrea Arcangeli <aarcange@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Axel Rasmussen <axelrasmussen@...gle.com>,
	Baolin Wang <baolin.wang@...ux.alibaba.com>,
	David Hildenbrand <david@...hat.com>,
	Hugh Dickins <hughd@...gle.com>,
	James Houghton <jthoughton@...gle.com>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Michal Hocko <mhocko@...e.com>,
	Mike Rapoport <rppt@...nel.org>,
	Nikita Kalyazin <kalyazin@...zon.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Peter Xu <peterx@...hat.com>,
	Sean Christopherson <seanjc@...gle.com>,
	Shuah Khan <shuah@...nel.org>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org,
	linux-kselftest@...r.kernel.org
Subject: [PATCH 0/5] mm, kvm: add guest_memfd support for uffd minor faults

From: "Mike Rapoport (Microsoft)" <rppt@...nel.org>

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