On 12/08/19 22:20, Sean Christopherson wrote: > The refcounting approach seems a bit backwards, and AFAICT is driven by > implementing unhook via a message, which also seems backwards. I assume > hook and unhook are relatively rare events and not performance critical, > so make those the restricted/slow flows, e.g. force userspace to quiesce > the VM by making unhook() mutually exclusive with every vcpu ioctl() and > maybe anything that takes kvm->lock. The reason for the unhook event, as far as I understand, is because the introspection appliance can poke int3 into the guest and needs an opportunity to undo that. I don't have a big problem with that and the refcounting, at least for this first iteration---it can be tackled later, once the general event loop is simplified---however I agree with the other comments that Sean made. Fortunately it should not be hard to apply them to the whole patchset with search and replace on the patches themselves. Paolo
