Re: [PATCH 14/22] KVM: x86/mmu: Morph kvm_handle_gfn_range() into an aging specific helper

From: David Matlack
Date: Mon Aug 12 2024 - 17:54:10 EST


On Fri, Aug 9, 2024 at 12:48 PM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 0a33857d668a..88b656a1453d 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> +static bool kvm_rmap_age_gfn_range(struct kvm *kvm,
> + struct kvm_gfn_range *range, bool test_only)
> +{
> + struct slot_rmap_walk_iterator iterator;
> + struct rmap_iterator iter;
> + bool young = false;
> + u64 *sptep;
> +
> + for_each_slot_rmap_range(range->slot, PG_LEVEL_4K, KVM_MAX_HUGEPAGE_LEVEL,
> + range->start, range->end - 1, &iterator) {
> + for_each_rmap_spte(iterator.rmap, &iter, sptep) {
> + if (test_only && is_accessed_spte(*sptep))
> + return true;
> +
> + young = mmu_spte_age(sptep);

It's jarring to see that mmu_spte_age() can get called in the
test_only case, even though I think the code is technically correct
(it will only be called if !is_accessed_spte() in which case
mmu_spte_age() will do nothing).