This series adds restricted mmap() support to guest_memfd, as well as support for guest_memfd on arm64. Please see v3 for the context [1]. Main change since v6 [2]: Protected the shared_offsets array with a rwlock instead of hopping on the invalidate_lock. The main reason for this is that the final put callback (kvm_gmem_handle_folio_put()) could be called from an atomic context, and the invalidate_lock is an rw_semaphore (Vishal). The other reason is, in hindsight, it didn't make sense to use the invalidate_lock since they're not quite protecting the same thing. I did consider using the folio lock to implicitly protect the array, and even have another series that does that. The result was more complicated, and not obviously race free. One of the difficulties with relying on the folio lock is that there are cases (e.g., on initilization and teardown) when we want to toggle the state of an offset that doesn't have a folio in the cache. We could special case these, but the result was more complicated (and to me not obviously better) than adding a separate lock for the shared_offsets array. Based on the `KVM: Mapping guest_memfd backed memory at the host for software protected VMs` series [3], which in turn is based on Linux 6.14-rc7. The state diagram that uses the new states in this patch series, and how they would interact with sharing/unsharing in pKVM [4]. Cheers, /fuad [1] https://lore.kernel.org/all/20241010085930.1546800-1-tabba@xxxxxxxxxx/ [2] https://lore.kernel.org/all/20250318162046.4016367-1-tabba@xxxxxxxxxx/ [3] https://lore.kernel.org/all/20250318161823.4005529-1-tabba@xxxxxxxxxx/ [4] 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 folio sharing within a struct kvm_gmem_private Fuad Tabba (5): KVM: guest_memfd: Introduce kvm_gmem_get_pfn_locked(), which retains the folio lock KVM: guest_memfd: Folio sharing states and functions that manage their transition KVM: guest_memfd: Restore folio state after final folio_put() KVM: guest_memfd: Handle invalidation of shared memory KVM: guest_memfd: Add a guest_memfd() flag to initialize it as shared Documentation/virt/kvm/api.rst | 4 + include/linux/kvm_host.h | 56 +- include/uapi/linux/kvm.h | 1 + include/uapi/linux/magic.h | 1 + .../testing/selftests/kvm/guest_memfd_test.c | 7 +- virt/kvm/guest_memfd.c | 613 +++++++++++++++++- virt/kvm/kvm_main.c | 62 ++ 7 files changed, 706 insertions(+), 38 deletions(-) base-commit: 62aff24816ac463bf3f754a15b2e7cdff59976ea -- 2.49.0.472.ge94155a9ec-goog
