On Thu, 2025-04-24 at 11:07 +0800, Yan Zhao wrote:
> +static int split_external_spt(struct kvm *kvm, gfn_t gfn, u64 old_spte,
> + u64 new_spte, int level)
> +{
> + void *external_spt = get_external_spt(gfn, new_spte, level);
> + int ret;
> +
> + KVM_BUG_ON(!external_spt, kvm);
> +
> + ret = static_call(kvm_x86_split_external_spt)(kvm, gfn, level, external_spt);
> + KVM_BUG_ON(ret, kvm);
Shouldn't this BUG_ON be handled in the split_external_spt implementation? I
don't think we need another one.
> +
> + return ret;
> +}
> /**
> * handle_removed_pt() - handle a page table removed from the TDP structure
> *
> @@ -764,13 +778,13 @@ static u64 tdp_mmu_set_spte(struct kvm *kvm, int as_id, tdp_ptep_t sptep,
>
> handle_changed_spte(kvm, as_id, gfn, old_spte, new_spte, level, false);
>
> - /*
> - * 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)) {
> - KVM_BUG_ON(is_shadow_present_pte(new_spte), kvm);
> - remove_external_spte(kvm, gfn, old_spte, level);
> + if (!is_shadow_present_pte(new_spte))
> + remove_external_spte(kvm, gfn, old_spte, level);
> + else if (is_last_spte(old_spte, level) && !is_last_spte(new_spte, level))
> + split_external_spt(kvm, gfn, old_spte, new_spte, level);
> + else
> + KVM_BUG_ON(1, kvm);
It might be worth a comment what this is looking for at this point. I think it's
that external EPT only support certain operations, so bug if any unsupported
operations are seen.
> }
>
> return old_spte;
