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Message-ID: <CABgObfYPpmyTyC94OgSqRPmR_ejuhHg4f_gLL=fo1vb4u8n35w@mail.gmail.com>
Date: Wed, 26 Nov 2025 09:33:20 +0100
From: Paolo Bonzini <pbonzini@...hat.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [GIT PULL] KVM: guest_memfd: NUMA support and other changes for 6.19
On Wed, Nov 26, 2025 at 2:45 AM Sean Christopherson <seanjc@...gle.com> wrote:
>
> Please pull NUMA mempolicy guest_memfd support, along with a handful of
> guest_memfd cleanups and some tangentially related additions to KVM selftests
> infrastructure.
>
> This will conflict with kvm/master due to commit ae431059e75d ("KVM:
> guest_memfd: Remove bindings on memslot deletion when gmem is dying"). The
> resolution I've been using for linux-next is below.
Pulled, thanks.
Paolo
> --
> diff --cc virt/kvm/guest_memfd.c
> index ffadc5ee8e04,427c0acee9d7..fdaea3422c30
> --- a/virt/kvm/guest_memfd.c
> +++ b/virt/kvm/guest_memfd.c
> @@@ -623,53 -708,31 +708,49 @@@ err
> return r;
> }
>
> - static void __kvm_gmem_unbind(struct kvm_memory_slot *slot, struct kvm_gmem *gmem)
> -void kvm_gmem_unbind(struct kvm_memory_slot *slot)
> ++static void __kvm_gmem_unbind(struct kvm_memory_slot *slot, struct gmem_file *f)
> {
> unsigned long start = slot->gmem.pgoff;
> unsigned long end = start + slot->npages;
> - struct gmem_file *f;
>
> - xa_store_range(&gmem->bindings, start, end - 1, NULL, GFP_KERNEL);
> - /*
> - * Nothing to do if the underlying file was already closed (or is being
> - * closed right now), kvm_gmem_release() invalidates all bindings.
> - */
> - CLASS(gmem_get_file, file)(slot);
> - if (!file)
> - return;
> -
> - f = file->private_data;
> -
> - filemap_invalidate_lock(file->f_mapping);
> + xa_store_range(&f->bindings, start, end - 1, NULL, GFP_KERNEL);
>
> /*
> * synchronize_srcu(&kvm->srcu) ensured that kvm_gmem_get_pfn()
> * cannot see this memslot.
> */
> WRITE_ONCE(slot->gmem.file, NULL);
> +}
> +
> +void kvm_gmem_unbind(struct kvm_memory_slot *slot)
> +{
> - struct file *file;
> -
> + /*
> + * Nothing to do if the underlying file was _already_ closed, as
> + * kvm_gmem_release() invalidates and nullifies all bindings.
> + */
> + if (!slot->gmem.file)
> + return;
> +
> - file = kvm_gmem_get_file(slot);
> ++ CLASS(gmem_get_file, file)(slot);
> +
> + /*
> + * However, if the file is _being_ closed, then the bindings need to be
> + * removed as kvm_gmem_release() might not run until after the memslot
> + * is freed. Note, modifying the bindings is safe even though the file
> + * is dying as kvm_gmem_release() nullifies slot->gmem.file under
> + * slots_lock, and only puts its reference to KVM after destroying all
> + * bindings. I.e. reaching this point means kvm_gmem_release() hasn't
> + * yet destroyed the bindings or freed the gmem_file, and can't do so
> + * until the caller drops slots_lock.
> + */
> + if (!file) {
> + __kvm_gmem_unbind(slot, slot->gmem.file->private_data);
> + return;
> + }
> +
> + filemap_invalidate_lock(file->f_mapping);
> + __kvm_gmem_unbind(slot, file->private_data);
> filemap_invalidate_unlock(file->f_mapping);
> -
> - fput(file);
> }
>
> /* Returns a locked folio on success. */
>
>
> The following changes since commit 211ddde0823f1442e4ad052a2f30f050145ccada:
>
> Linux 6.18-rc2 (2025-10-19 15:19:16 -1000)
>
> are available in the Git repository at:
>
> https://github.com/kvm-x86/linux.git tags/kvm-x86-gmem-6.19
>
> for you to fetch changes up to 83e0e12219a402bf7b8fdef067e51f945a92fd26:
>
> KVM: selftests: Rename "guest_paddr" variables to "gpa" (2025-11-03 12:54:21 -0800)
>
> ----------------------------------------------------------------
> KVM guest_memfd changes for 6.19:
>
> - Add NUMA mempolicy support for guest_memfd, and clean up a variety of
> rough edges in guest_memfd along the way.
>
> - Define a CLASS to automatically handle get+put when grabbing a guest_memfd
> from a memslot to make it harder to leak references.
>
> - Enhance KVM selftests to make it easer to develop and debug selftests like
> those added for guest_memfd NUMA support, e.g. where test and/or KVM bugs
> often result in hard-to-debug SIGBUS errors.
>
> - Misc cleanups.
>
> ----------------------------------------------------------------
> Ackerley Tng (1):
> KVM: guest_memfd: Use guest mem inodes instead of anonymous inodes
>
> Matthew Wilcox (2):
> mm/filemap: Add NUMA mempolicy support to filemap_alloc_folio()
> mm/filemap: Extend __filemap_get_folio() to support NUMA memory policies
>
> Pedro Demarchi Gomes (1):
> KVM: guest_memfd: use folio_nr_pages() instead of shift operation
>
> Sean Christopherson (10):
> KVM: guest_memfd: Drop a superfluous local var in kvm_gmem_fault_user_mapping()
> 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
> KVM: guest_memfd: Define a CLASS to get+put guest_memfd file from a memslot
> KVM: selftests: Rename "guest_paddr" variables to "gpa"
>
> Shivank Garg (7):
> mm/mempolicy: Export memory policy symbols
> KVM: guest_memfd: move kvm_gmem_get_index() and use in kvm_gmem_prepare_folio()
> KVM: guest_memfd: remove redundant gmem variable initialization
> 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
>
> fs/btrfs/compression.c | 4 +-
> fs/btrfs/verity.c | 2 +-
> fs/erofs/zdata.c | 2 +-
> fs/f2fs/compress.c | 2 +-
> include/linux/pagemap.h | 18 +++--
> include/uapi/linux/magic.h | 1 +
> mm/filemap.c | 23 ++++---
> mm/mempolicy.c | 6 ++
> mm/readahead.c | 2 +-
> tools/testing/selftests/kvm/arm64/vgic_irq.c | 2 +-
> tools/testing/selftests/kvm/guest_memfd_test.c | 98 +++++++++++++++++++++++++++
> tools/testing/selftests/kvm/include/kvm_syscalls.h | 81 ++++++++++++++++++++++
> tools/testing/selftests/kvm/include/kvm_util.h | 39 ++---------
> tools/testing/selftests/kvm/include/numaif.h | 110 ++++++++++++++++++------------
> tools/testing/selftests/kvm/kvm_binary_stats_test.c | 4 +-
> tools/testing/selftests/kvm/lib/kvm_util.c | 101 +++++++++++++++-------------
> tools/testing/selftests/kvm/x86/private_mem_conversions_test.c | 9 +--
> tools/testing/selftests/kvm/x86/xapic_ipi_test.c | 5 +-
> virt/kvm/guest_memfd.c | 374 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++--------------------------
> virt/kvm/kvm_main.c | 7 +-
> virt/kvm/kvm_mm.h | 9 +--
> 21 files changed, 646 insertions(+), 253 deletions(-)
> create mode 100644 tools/testing/selftests/kvm/include/kvm_syscalls.h
>
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