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

Fuad Tabba
2024-12-13T16:48:14Z

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