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

Ackerley Tng
2025-10-09T20:58:40Z

Sean Christopherson <seanjc@google.com> writes:

> 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

For future reference, these are the three specific patches:

[1] https://lore.kernel.org/all/20250827175247.83322-4-shivankg@amd.com/
[2] https://lore.kernel.org/all/20250827175247.83322-5-shivankg@amd.com/
[3] https://lore.kernel.org/all/20250827175247.83322-6-shivankg@amd.com/

Might have missed this, did we discuss how these 3 would get merged? I
noticed this patch was withdrawn, not sure what that means: [4]

[4] https://lore.kernel.org/all/20250625000155.62D08C4CEE3@smtp.kernel.org/

> (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