On Sun, Dec 22, 2024, Paolo Bonzini wrote:
> + /* Because write lock is held, operation should success. */
succeed.
> + ret = static_call(kvm_x86_remove_external_spte)(kvm, gfn, level, old_pfn);
> + KVM_BUG_ON(ret, kvm);
> +}
> +
> /**
> * handle_removed_pt() - handle a page table removed from the TDP structure
> *
> @@ -435,6 +458,23 @@ static void handle_removed_pt(struct kvm *kvm, tdp_ptep_t pt, bool shared)
> }
> handle_changed_spte(kvm, kvm_mmu_page_as_id(sp), gfn,
> old_spte, FROZEN_SPTE, level, shared);
> +
> + if (is_mirror_sp(sp)) {
> + KVM_BUG_ON(shared, kvm);
Should these bail early if the KVM_BUG_ON() is hit? Calling into the TDX module
after bugging the VM is a bit odd.
> + remove_external_spte(kvm, gfn, old_spte, level);
> + }
> + }
> +
> + if (is_mirror_sp(sp) &&
> + WARN_ON(static_call(kvm_x86_free_external_spt)(kvm, base_gfn, sp->role.level,
WARN_ON_ONCE(). I suspect that if this ever gets hit, it'll come in bunches.
> + sp->external_spt))) {
> + /*
> + * Failed to free page table page in mirror page table and
> + * there is nothing to do further.
> + * Intentionally leak the page to prevent the kernel from
> + * accessing the encrypted page.
> + */
> + sp->external_spt = NULL;
> }
>
> call_rcu(&sp->rcu_head, tdp_mmu_free_sp_rcu_callback);
> @@ -608,6 +648,13 @@ static inline int __must_check __tdp_mmu_set_spte_atomic(struct kvm *kvm,
> if (is_mirror_sptep(iter->sptep) && !is_frozen_spte(new_spte)) {
> int ret;
>
> + /*
> + * Users of atomic zapping don't operate on mirror roots,
> + * so don't handle it and bug the VM if it's seen.
> + */
> + if (KVM_BUG_ON(!is_shadow_present_pte(new_spte), kvm))
> + return -EBUSY;
> +
> ret = set_external_spte_present(kvm, iter->sptep, iter->gfn,
> iter->old_spte, new_spte, iter->level);
> if (ret)
> @@ -700,8 +747,10 @@ static u64 tdp_mmu_set_spte(struct kvm *kvm, int as_id, tdp_ptep_t sptep,
> * Users that do non-atomic setting of PTEs don't operate on mirror
> * roots, so don't handle it and bug the VM if it's seen.
> */
> - if (is_mirror_sptep(sptep))
> + if (is_mirror_sptep(sptep)) {
> KVM_BUG_ON(is_shadow_present_pte(new_spte), kvm);
> + remove_external_spte(kvm, gfn, old_spte, level);
> + }
>
> return old_spte;
> }
> --
> 2.43.5
>
>
