On Wed, Sep 11, 2024 at 07:58:01AM +0800, Edgecombe, Rick P wrote: > On Tue, 2024-09-10 at 11:33 +0200, Paolo Bonzini wrote: > > > But actually, I wonder if we need to remove the KVM_BUG_ON(). I think if you > > > did > > > a KVM_PRE_FAULT_MEMORY and then deleted the memslot you could hit it? > > > > I think all paths to handle_removed_pt() are safe: > > > > __tdp_mmu_zap_root > > tdp_mmu_zap_root > > kvm_tdp_mmu_zap_all > > kvm_arch_flush_shadow_all > > kvm_flush_shadow_all > > kvm_destroy_vm (*) > > kvm_mmu_notifier_release (*) > > kvm_tdp_mmu_zap_invalidated_roots > > kvm_mmu_zap_all_fast (**) > > kvm_tdp_mmu_zap_sp > > kvm_recover_nx_huge_pages (***) > > But not all paths to remove_external_spte(): > kvm_arch_flush_shadow_memslot() > kvm_mmu_zap_memslot_leafs() > kvm_tdp_mmu_unmap_gfn_range() > tdp_mmu_zap_leafs() > tdp_mmu_iter_set_spte() > tdp_mmu_set_spte() > remove_external_spte() > tdx_sept_remove_private_spte() > > But we can probably keep the warning if we prevent KVM_PRE_FAULT_MEMORY as you > pointed earlier. I didn't see that that kvm->arch.pre_fault_allowed got added. Note: If we diallow vCPU to be created before vm ioctl KVM_TDX_INIT_VM is done, the vCPU ioctl KVM_PRE_FAULT_MEMORY can't be executed. Then we can't hit the "if (KVM_BUG_ON(!is_hkid_assigned(to_kvm_tdx(kvm)), kvm))" in tdx_sept_remove_private_spte().
