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

Steffen Eiden
2026-04-09T15:07:06Z

On Tue, Apr 07, 2026 at 08:01:04PM +0200, Paolo Bonzini 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
>

...

Thanks for sending/fixing the issue. LGTM.

For v2 of the arm-on-s390 series I'll drop the (first )three patches and
depend on this series. So we can merge them early. OK?

Steffen