[PATCH v4 00/10] KVM: Mapping guest_memfd backed memory at the host for software protected VMs

[Fuad Tabba <tabba@google.com>]

Main changes since v3 [1]:
- Dropped the arm64 sw protected vm type. Instead,
non-confidential arm64 VM types support guest_memfd with sharing
in place when the configuration option is enabled. Future VM
types can restrict that.
- Expand the guest_memfd host fault error return values to cover
more cases.
- Fixes to faulting in guest_memfd pages in arm64.
- Rebased on Linux 6.14-rc3.

The purpose of this series is to serve as a base for _restricted_
mmap() support for guest_memfd backed memory at the host [2]. It
allows experimentation with what that support would be like in
the safe environment of software and non-confidential VM types.

For more background and for how to test this series, please refer
to v2 [3]. Note that an updated version of kvmtool that works
with this series is available here [4].

Cheers,
/fuad

[1] https://lore.kernel.org/all/20250211121128.703390-1-tabba@google.com/
[2] https://lore.kernel.org/all/20250117163001.2326672-1-tabba@google.com/
[3] https://lore.kernel.org/all/20250129172320.950523-1-tabba@google.com/
[4] https://android-kvm.googlesource.com/kvmtool/+/refs/heads/tabba/guestmem-6.14

Fuad Tabba (10):
  mm: Consolidate freeing of typed folios on final folio_put()
  KVM: guest_memfd: Handle final folio_put() of guest_memfd pages
  KVM: guest_memfd: Allow host to map guest_memfd() pages
  KVM: guest_memfd: Add KVM capability to check if guest_memfd is shared
  KVM: guest_memfd: Handle in-place shared memory as guest_memfd backed
    memory
  KVM: x86: Mark KVM_X86_SW_PROTECTED_VM as supporting guest_memfd
    shared memory
  KVM: arm64: Refactor user_mem_abort() calculation of force_pte
  KVM: arm64: Handle guest_memfd()-backed guest page faults
  KVM: arm64: Enable mapping guest_memfd in arm64
  KVM: guest_memfd: selftests: guest_memfd mmap() test when mapping is
    allowed

 arch/arm64/include/asm/kvm_host.h             |  10 ++
 arch/arm64/kvm/Kconfig                        |   1 +
 arch/arm64/kvm/mmu.c                          |  83 ++++++++-----
 arch/x86/include/asm/kvm_host.h               |   5 +
 arch/x86/kvm/Kconfig                          |   3 +-
 include/linux/kvm_host.h                      |  23 +++-
 include/linux/page-flags.h                    |  32 +++++
 include/uapi/linux/kvm.h                      |   1 +
 mm/debug.c                                    |   1 +
 mm/swap.c                                     |  32 ++++-
 tools/testing/selftests/kvm/Makefile.kvm      |   1 +
 .../testing/selftests/kvm/guest_memfd_test.c  |  75 +++++++++++-
 virt/kvm/Kconfig                              |   5 +
 virt/kvm/guest_memfd.c                        | 110 ++++++++++++++++++
 virt/kvm/kvm_main.c                           |   9 +-
 15 files changed, 345 insertions(+), 46 deletions(-)


base-commit: 0ad2507d5d93f39619fc42372c347d6006b64319
-- 
2.48.1.601.g30ceb7b040-goog