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[RFC,v5,00/15] KVM: Restricted mapping of guest_memfd at the host and arm64 support

Message ID 20250117163001.2326672-1-tabba@google.com (mailing list archive)
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Series KVM: Restricted mapping of guest_memfd at the host and arm64 support | expand

Message

Fuad Tabba Jan. 17, 2025, 4:29 p.m. UTC 
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-rc7.  Please refer to v3 for the context [1].

Main changes since v4 [2]:
- Fixed handling of guest_memfd()-backed page faults in arm64
- Rebased on Linux 6.13-rc7

Not a change per se, but I am able to trigger/test the callback
on the final __folio_put() using vmsplice to grab a reference
without increasing the mapcount.

The state diagram that uses the new states in this patch series,
and how they would interact with sharing/unsharing in pKVM [3].

Cheers,
/fuad

[1] https://lore.kernel.org/all/20241010085930.1546800-1-tabba@google.com/
[2] https://lore.kernel.org/all/20241213164811.2006197-1-tabba@google.com/
[3] https://lpc.events/event/18/contributions/1758/attachments/1457/3699/Guestmemfd%20folio%20state%20page_type.pdf

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 (13):
  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: Refactor user_mem_abort() calculation of force_pte
  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                          |  98 ++-
 include/linux/kvm_host.h                      |  80 +++
 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                           | 234 ++++++-
 15 files changed, 1034 insertions(+), 88 deletions(-)


base-commit: 5bc55a333a2f7316b58edc7573e8e893f7acb532