Re: [PATCH 0/3] KVM, vfio: remove exported KVM symbols

Alex Williamson
2026-04-07T20:16:35Z

On Tue, 7 Apr 2026 20:01:04 +0200
Paolo Bonzini <pbonzini@redhat.com> wrote:

> KVM right now exports three symbols for the whole kernel to manage
> the reference count of "struct kvm"; these are used by VFIO just to
> keep the "struct kvm" alive. This can mostly be replaced
> by inlines, and in fact the entire definition of struct kvm can be
> made opaque to VFIO.
>
> Besides the cleanup of removing the sort-of-deprecated symbol_get() and
> the bidirectional dependency between KVM and VFIO, this is useful for
> the recently posted support for Arm VMs on s390. In that scenario each
> KVM implementation module wants to have its own copy of kvm_put_kvm()
> in order to call the "right" kvm_destroy_vm(). With multiple modules,
> VFIO has no way to do a symbol_get() from the right module.
>
> With this series, that problem is gone because kvm_put_kvm dispatches
> through a function pointer, set by whichever implementation creates the VM.
> The main issue is that symbol_get() was implicitly taking a reference
> to the KVM module, and that has to be preserved. This is the purpose
> of patch 1.
>
> Thanks,
>
> Paolo
>
> Paolo Bonzini (3):
> VFIO: take reference to the KVM module
> KVM, vfio: remove symbol_get(kvm_get_kvm_safe) from vfio
> KVM, vfio: remove symbol_get(kvm_put_kvm) from vfio
>
> arch/x86/kvm/mmu/tdp_mmu.c | 2 +-
> arch/x86/kvm/vmx/nested.h | 4 +--
> drivers/vfio/device_cdev.c | 2 +-
> drivers/vfio/group.c | 5 ++--
> drivers/vfio/vfio.h | 15 +++++++----
> drivers/vfio/vfio_main.c | 51 ++++++++++++++------------------------
> include/linux/kvm_host.h | 9 +++----
> include/linux/kvm_types.h | 30 ++++++++++++++++++++++
> include/linux/vfio.h | 4 +--
> virt/kvm/kvm_main.c | 34 ++++++-------------------
> virt/kvm/vfio.c | 4 +--
> 11 files changed, 80 insertions(+), 80 deletions(-)
>

Looks clean.

Acked-by: Alex Williamson <alex@shazbot.org>