Re: [RFC PATCH 14/21] KVM: x86/tdp_mmu: Invoke split_external_spt hook with exclusive mmu_lock

[Binbin Wu]

On 4/24/2025 11:07 AM, 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);
Better to use kvm_x86_call() instead of static_call().

> +	KVM_BUG_ON(ret, kvm);
> +
> +	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);
>   	}
>   
>   	return old_spte;