On Fri, Sep 25, 2020 at 6:04 PM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > > On 25/09/20 23:22, Ben Gardon wrote: > > start_level, KVM_MAX_HUGEPAGE_LEVEL, false); > > + if (kvm->arch.tdp_mmu_enabled) > > + flush = kvm_tdp_mmu_wrprot_slot(kvm, memslot, false) || flush; > > spin_unlock(&kvm->mmu_lock); > > > > In fact you can just pass down the end-level KVM_MAX_HUGEPAGE_LEVEL or > PGLEVEL_4K here to kvm_tdp_mmu_wrprot_slot and from there to > wrprot_gfn_range. That makes sense. My only worry there is the added complexity of error handling values besides PG_LEVEL_2M and PG_LEVEL_4K. Since there are only two callers, I don't think that will be too much of a problem though. I don't think KVM_MAX_HUGEPAGE_LEVEL would actually be a good value to pass in as I don't think that would write protect 2M mappings. KVM_MAX_HUGEPAGE_LEVEL is defined as PG_LEVEL_1G, or 3. > > > > > + /* > > + * Take a reference on the root so that it cannot be freed if > > + * this thread releases the MMU lock and yields in this loop. > > + */ > > + get_tdp_mmu_root(kvm, root); > > + > > + spte_set = wrprot_gfn_range(kvm, root, slot->base_gfn, > > + slot->base_gfn + slot->npages, skip_4k) || > > + spte_set; > > + > > + put_tdp_mmu_root(kvm, root); > > > Generalyl using "|=" is the more common idiom in mmu.c. I changed to this in response to some feedback on the RFC, about mixing bitwise ops and bools, but I like the |= syntax more as well. > > > +static bool clear_dirty_gfn_range(struct kvm *kvm, struct kvm_mmu_page *root, > > + gfn_t start, gfn_t end) > > ... > > + __handle_changed_spte(kvm, as_id, iter.gfn, iter.old_spte, > > + new_spte, iter.level); > > + handle_changed_spte_acc_track(iter.old_spte, new_spte, > > + iter.level); > > Is it worth not calling handle_changed_spte? handle_changed_spte_dlog > obviously will never fire but duplicating the code is a bit ugly. > > I guess this patch is the first one that really gives the "feeling" of > what the data structures look like. The main difference with the shadow > MMU is that you have the tdp_iter instead of the callback-based code of > slot_handle_level_range, but otherwise it's not hard to follow one if > you know the other. Reorganizing the code so that mmu.c is little more > than a wrapper around the two will help as well in this respect. > > Paolo >
