Hi, As mentioned in the guest_memfd sync (2025-01-09), below is the state diagram that uses the new states in this patch series, and how they would interact with sharing/unsharing in pKVM: https://lpc.events/event/18/contributions/1758/attachments/1457/3699/Guestmemfd%20folio%20state%20page_type.pdf This patch series doesn't necessarily impose all these transitions, many of them would be a matter of policy. This just happens to be the current way I've done it with pKVM/arm64. Cheers, /fuad On Fri, 13 Dec 2024 at 16:48, Fuad Tabba <tabba@xxxxxxxxxx> wrote: > > 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@xxxxxxxxxx/ > [2] https://lore.kernel.org/all/20241108162040.159038-1-tabba@xxxxxxxxxx/ > > 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 >
