Re: [PATCH v3 22/28] KVM: x86/mmu: Zap defunct roots via asynchronous worker

[Sean Christopherson]

On Wed, Mar 02, 2022, Paolo Bonzini wrote:
> However, I think we now need a module_get/module_put when creating/destroying
> a VM; the workers can outlive kvm_vm_release and therefore any reference
> automatically taken by VFS's fops_get/fops_put.

Haven't read the rest of the patch, but this caught my eye.  We _already_ need
to handle this scenario.  As you noted, any worker, i.e. anything that takes a
reference via kvm_get_kvm() without any additional guarantee that the module can't
be unloaded is suspect. x86 is mostly fine, though kvm_setup_async_pf() is likely
affected, and other architectures seem to have bugs.

Google has an internal patch that addresses this.  I believe David is going to post
the fix... David?