On Fri, Jun 07, 2024 at 09:46:27PM +0000, "Edgecombe, Rick P" <rick.p.edgecombe@xxxxxxxxx> wrote: > > /* Here we only care about zapping the external leaf PTEs. */ > > if (!is_last_spte(old_spte, level)) > > > > > + kvm_pfn_t old_pfn = spte_to_pfn(old_spte); > > > + int ret; > > > + > > > + /* > > > + * Allow only leaf page to be zapped. Reclaim non-leaf page tables > > > page > > > > This comment left me confused, so I'll try to rephrase and see if I > > can explain what happens. Correct me if I'm wrong. > > > > The only paths to handle_removed_pt() are: > > - kvm_tdp_mmu_zap_leafs() > > - kvm_tdp_mmu_zap_invalidated_roots() > > > > but because kvm_mmu_zap_all_fast() does not operate on mirror roots, > > the latter can only happen at VM destruction time. > > > > But it's not clear why it's worth mentioning it here, or even why it > > is special at all. Isn't that just what handle_removed_pt() does at > > the end? Why does it matter that it's only done at VM destruction > > time? > > > > In other words, it seems to me that this comment is TMI. And if I am > > wrong (which may well be), the extra information should explain the > > "why" in more detail, and it should be around the call to > > reflect_free_spt, not here. > > TDX of course has the limitation around the ordering of the zapping S-EPT. So I > read the comment to be referring to how the implementation avoids zapping any > non-leaf PTEs during TD runtime. > > But I'm going to have to circle back here after investigating a bit more. Isaku, > any comments on this comment and conditional? It's for large page page merge/split. At this point, it seems only confusing. We need only leaf zapping. Maybe reflect_removed_leaf_spte() or something. Later we can come back when large page support. -- Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
