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

Paolo Bonzini
2022-03-02T18:36:20Z

On 3/2/22 19:33, David Matlack wrote:
> On Wed, Mar 2, 2022 at 9:35 AM Sean Christopherson <seanjc@google.com> wrote:
>>
>> 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?
>
> This was towards the back of my queue but I can bump it to the front.
> I'll have the patches out this week.

Thanks!

Paolo