On 3/2/22 20:33, Sean Christopherson wrote:
What about that idea? Put roots invalidated by "fast zap" on_another_ list? My very original idea of moving the roots to a separate list didn't work because the roots needed to be reachable by the mmu_notifier. But we could just add another list_head (inside the unsync_child_bitmap union) and add the roots to _that_ list.
Perhaps the "separate list" idea could be extended to have a single worker for all kvm_tdp_mmu_put_root() work, and then indeed replace kvm_tdp_mmu_zap_invalidated_roots() with a flush of _that_ worker. The disadvantage is a little less parallelism in zapping invalidated roots; but what is good for kvm_tdp_mmu_zap_invalidated_roots() is just as good for kvm_tdp_mmu_put_root(), I suppose. If one wants separate work items, KVM could have its own workqueue, and then you flush that workqueue.
For now let's do it the simple but ugly way. Keeping next_invalidated_root() does not make things worse than the status quo, and further work will be easier to review if it's kept separate from this already-complex work.
Paolo
