Message-ID: <diqz5xcniyhb.fsf@google.com>
Date: Thu, 09 Oct 2025 13:58:24 -0700
From: Ackerley Tng <ackerleytng@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Marc Zyngier <maz@...nel.org>, 
	Oliver Upton <oliver.upton@...ux.dev>, Paolo Bonzini <pbonzini@...hat.com>
Cc: linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev, 
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	David Hildenbrand <david@...hat.com>, Fuad Tabba <tabba@...gle.com>, Shivank Garg <shivankg@....com>, 
	Ashish Kalra <ashish.kalra@....com>, Vlastimil Babka <vbabka@...e.cz>
Subject: Re: [PATCH v12 00/12] KVM: guest_memfd: Add NUMA mempolicy support

Sean Christopherson <seanjc@...gle.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noticed this patch was withdrawn, not sure what that means: [4]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

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