[RFC PATCH v4 00/14] KVM: Restricted mapping of guest_memfd at the host and arm64 support

[Fuad Tabba <tabba@google.com>]

This series adds restricted mmap() support to guest_memfd, as
well as support for guest_memfd on arm64. It is based on Linux
6.13-rc2.  Please refer to v3 for the context [1].

Main changes since v3:
- Added a new folio type for guestmem, used to register a
  callback when a folio's reference count reaches 0 (Matthew
  Wilcox, DavidH) [2]
- Introduce new mappability states for folios, where a folio can
be mappable by the host and the guest, only the guest, or by no
one (transient state)
- Rebased on Linux 6.13-rc2
- Refactoring and tidying up

Cheers,
/fuad

[1] https://lore.kernel.org/all/20241010085930.1546800-1-tabba@google.com/
[2] https://lore.kernel.org/all/20241108162040.159038-1-tabba@google.com/

Ackerley Tng (2):
  KVM: guest_memfd: Make guest mem use guest mem inodes instead of
    anonymous inodes
  KVM: guest_memfd: Track mappability within a struct kvm_gmem_private

Fuad Tabba (12):
  mm: Consolidate freeing of typed folios on final folio_put()
  KVM: guest_memfd: Introduce kvm_gmem_get_pfn_locked(), which retains
    the folio lock
  KVM: guest_memfd: Folio mappability states and functions that manage
    their transition
  KVM: guest_memfd: Handle final folio_put() of guestmem pages
  KVM: guest_memfd: Allow host to mmap guest_memfd() pages when shared
  KVM: guest_memfd: Add guest_memfd support to
    kvm_(read|/write)_guest_page()
  KVM: guest_memfd: Add KVM capability to check if guest_memfd is host
    mappable
  KVM: guest_memfd: Add a guest_memfd() flag to initialize it as
    mappable
  KVM: guest_memfd: selftests: guest_memfd mmap() test when mapping is
    allowed
  KVM: arm64: Skip VMA checks for slots without userspace address
  KVM: arm64: Handle guest_memfd()-backed guest page faults
  KVM: arm64: Enable guest_memfd private memory when pKVM is enabled

 Documentation/virt/kvm/api.rst                |   4 +
 arch/arm64/include/asm/kvm_host.h             |   3 +
 arch/arm64/kvm/Kconfig                        |   1 +
 arch/arm64/kvm/mmu.c                          | 119 +++-
 include/linux/kvm_host.h                      |  75 +++
 include/linux/page-flags.h                    |  22 +
 include/uapi/linux/kvm.h                      |   2 +
 include/uapi/linux/magic.h                    |   1 +
 mm/debug.c                                    |   1 +
 mm/swap.c                                     |  28 +-
 tools/testing/selftests/kvm/Makefile          |   1 +
 .../testing/selftests/kvm/guest_memfd_test.c  |  64 +-
 virt/kvm/Kconfig                              |   4 +
 virt/kvm/guest_memfd.c                        | 579 +++++++++++++++++-
 virt/kvm/kvm_main.c                           | 229 ++++++-
 15 files changed, 1074 insertions(+), 59 deletions(-)


base-commit: fac04efc5c793dccbd07e2d59af9f90b7fc0dca4
-- 
2.47.1.613.gc27f4b7a9f-goog