On Wed, Mar 31, 2021 at 3:27 PM Sean Christopherson <seanjc@xxxxxxxxxx> wrote: > > On Wed, Mar 31, 2021, Ben Gardon wrote: > > Provide a real mechanism for fast invalidation by marking roots as > > invalid so that their reference count will quickly fall to zero > > and they will be torn down. > > > > One negative side affect of this approach is that a vCPU thread will > > likely drop the last reference to a root and be saddled with the work of > > tearing down an entire paging structure. This issue will be resolved in > > a later commit. > > > > Signed-off-by: Ben Gardon <bgardon@xxxxxxxxxx> > > --- > > ... > > > +/* > > + * This function depends on running in the same MMU lock cirical section as > > + * kvm_reload_remote_mmus. Since this is in the same critical section, no new > > + * roots will be created between this function and the MMU reload signals > > + * being sent. > > Eww. That goes beyond just adding a lockdep assertion here. I know you want to > isolate the TDP MMU as much as possible, but this really feels like it should be > open coded in kvm_mmu_zap_all_fast(). And assuming this lands after as_id is > added to for_each_tdp_mmu_root(), it's probably easier to open code anyways, e.g. > use list_for_each_entry() directly instead of bouncing through an iterator. Yeah, that's fair. I'll open-code it here. I agree that it will remove confusion from the function, though it would be nice to be able to use for_each_tdp_mmu_root for the lockdep and rcu annotations. > > > + */ > > +void kvm_tdp_mmu_invalidate_roots(struct kvm *kvm) > > +{ > > + struct kvm_mmu_page *root; > > + > > + for_each_tdp_mmu_root(kvm, root) > > + root->role.invalid = true; > > +}