Re: [PATCH 05/22] kvm: mmu: Add functions to handle changed TDP SPTEs

[Paolo Bonzini]

On 26/09/20 02:39, Paolo Bonzini wrote:
>> +handle_changed_spte(kvm, as_id,
>> +gfn + (i * KVM_PAGES_PER_HPAGE(level - 1)),
>> +old_child_spte, 0, level - 1);
>> +}
> Is it worth returning a "flush" value to the caller, to avoid multiple
> kvm_flush_remote_tlbs_with_address when e.g. zapping a 3rd-level PTE?

Nevermind, this is not possible since you are freeing the page
immediately after kvm_flush_remote_tlbs_with_address.

Paolo

Re: [PATCH 05/22] kvm: mmu: Add functions to handle changed TDP SPTEs

[Paolo Bonzini]

On 25/09/20 23:22, Ben Gardon wrote:
> +
> + /*
> +  * Recursively handle child PTs if the change removed a subtree from
> +  * the paging structure.
> +  */
> + if (was_present && !was_leaf && (pfn_changed || !is_present)) {
> + pt = spte_to_child_pt(old_spte, level);
> +
> + for (i = 0; i < PT64_ENT_PER_PAGE; i++) {
> + old_child_spte = *(pt + i);
> + *(pt + i) = 0;
> + handle_changed_spte(kvm, as_id,
> + gfn + (i * KVM_PAGES_PER_HPAGE(level - 1)),
> + old_child_spte, 0, level - 1);
> + }

Is it worth returning a "flush" value to the caller, to avoid multiple
kvm_flush_remote_tlbs_with_address when e.g. zapping a 3rd-level PTE?

Also I prefer if we already include here a "stupid" version of
handle_changed_spte that just calls __handle_changed_spte.  (If my
suggestion is accepted, handle_changed_spte could actually handle the
flushing).

Paolo

> +
> + kvm_flush_remote_tlbs_with_address(kvm, gfn,
> +KVM_PAGES_PER_HPAGE(level));
> +
> + free_page((unsigned long)pt);
> + }