[PATCH v12 00/12] KVM: guest_memfd: Add NUMA mempolicy support

Sean Christopherson
2025-10-07T22:14:37Z

Shivank's series to add support for NUMA-aware memory placement in
guest_memfd. This is based on:

https://github.com/kvm-x86/linux.git gmem

which is an unstable topic branch that contains the guest_memfd MMAP fixes
destined for 6.18 (to avoid conflicts), and three non-KVM changes related to
mempolicy that were in previous versions of this series (I want to keep this
version KVM focused, and AFAICT there is nothing left to discuss in the prep
paches).

Once 6.18-rc1 is cut I'll turn "gmem" into a proper topic branch, rebase it,
and freeze the hashes.

v12:
- Add missing functionality to KVM selftests' existing numaif.h instead of
linking to libnuma (which appears to have caveats with -static).
- Add KVM_SYSCALL_DEFINE() infrastructure to reduce the boilerplate needed
to wrap syscalls and/or to assert that a syscall succeeds.
- Rename kvm_gmem to gmem_file, and use gmem_inode for the inode structure.
- Track flags in a gmem_inode field instead of using i_private.
- Add comments to call out subtleties in the mempolicy code (e.g. that
returning NULL for vm_operations_struct.get_policy() is important for ABI
reasons).
- Improve debugability of guest_memfd_test (I kept generating SIGBUS when
tweaking the tests).
- Test mbind() with private memory (sadly, verifying placement with
move_pages() doesn't work due to the dependency on valid page tables).

- V11: Rebase on kvm-next, remove RFC tag, use Ackerley's latest patch
and fix a rcu race bug during kvm module unload.
- V10: Rebase on top of Fuad's V17. Use latest guest_memfd inode patch
from Ackerley (with David's review comments). Use newer kmem_cache_create()
API variant with arg parameter (Vlastimil)
- v9: Rebase on top of Fuad's V13 and incorporate review comments
- v8: Rebase on top of Fuad's V12: Host mmaping for guest_memfd memory.
- v7: Use inodes to store NUMA policy instead of file [0].
- v4-v6: Current approach using shared_policy support and vm_ops (based on
suggestions from David [1] and guest_memfd bi-weekly upstream
call discussion [2]).
- v3: Introduced fbind() syscall for VMM memory-placement configuration.
- v1,v2: Extended the KVM_CREATE_GUEST_MEMFD IOCTL to pass mempolicy.

[0] https://lore.kernel.org/all/diqzbjumm167.fsf@ackerleytng-ctop.c.googlers.com
[1] https://lore.kernel.org/all/6fbef654-36e2-4be5-906e-2a648a845278@redhat.com
[2] https://lore.kernel.org/all/2b77e055-98ac-43a1-a7ad-9f9065d7f38f@amd.com

Ackerley Tng (1):
KVM: guest_memfd: Use guest mem inodes instead of anonymous inodes

Sean Christopherson (7):
KVM: guest_memfd: Rename "struct kvm_gmem" to "struct gmem_file"
KVM: guest_memfd: Add macro to iterate over gmem_files for a
mapping/inode
KVM: selftests: Define wrappers for common syscalls to assert success
KVM: selftests: Report stacktraces SIGBUS, SIGSEGV, SIGILL, and SIGFPE
by default
KVM: selftests: Add additional equivalents to libnuma APIs in KVM's
numaif.h
KVM: selftests: Use proper uAPI headers to pick up mempolicy.h
definitions
KVM: guest_memfd: Add gmem_inode.flags field instead of using
i_private

Shivank Garg (4):
KVM: guest_memfd: Add slab-allocated inode cache
KVM: guest_memfd: Enforce NUMA mempolicy using shared policy
KVM: selftests: Add helpers to probe for NUMA support, and multi-node
systems
KVM: selftests: Add guest_memfd tests for mmap and NUMA policy support

include/uapi/linux/magic.h | 1 +
tools/testing/selftests/kvm/arm64/vgic_irq.c | 2 +-
.../testing/selftests/kvm/guest_memfd_test.c | 98 +++++
.../selftests/kvm/include/kvm_syscalls.h | 81 +++++
.../testing/selftests/kvm/include/kvm_util.h | 29 +-
tools/testing/selftests/kvm/include/numaif.h | 110 +++---
.../selftests/kvm/kvm_binary_stats_test.c | 4 +-
tools/testing/selftests/kvm/lib/kvm_util.c | 55 +--
.../kvm/x86/private_mem_conversions_test.c | 9 +-
.../selftests/kvm/x86/xapic_ipi_test.c | 5 +-
virt/kvm/guest_memfd.c | 344 ++++++++++++++----
virt/kvm/kvm_main.c | 7 +-
virt/kvm/kvm_mm.h | 9 +-
13 files changed, 576 insertions(+), 178 deletions(-)
create mode 100644 tools/testing/selftests/kvm/include/kvm_syscalls.h

base-commit: 67033eaa5ea2cb67b6cdaa91d7f5c42bfafb36f7
--
2.51.0.710.ga91ca5db03-goog