On Fri, Aug 13, 2021, David Matlack wrote:
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 3352312ab1c9..fb2c95e8df00 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -2890,7 +2890,7 @@ int kvm_mmu_max_mapping_level(struct kvm *kvm,
>
> void kvm_mmu_hugepage_adjust(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
> {
> - struct kvm_memory_slot *slot;
> + struct kvm_memory_slot *slot = fault->slot;
> kvm_pfn_t mask;
>
> fault->huge_page_disallowed = fault->exec && fault->nx_huge_page_workaround_enabled;
> @@ -2901,8 +2901,7 @@ void kvm_mmu_hugepage_adjust(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault
> if (is_error_noslot_pfn(fault->pfn) || kvm_is_reserved_pfn(fault->pfn))
> return;
>
> - slot = gfn_to_memslot_dirty_bitmap(vcpu, fault->gfn, true);
> - if (!slot)
> + if (kvm_slot_dirty_track_enabled(slot))
This is unnecessarily obfuscated. It relies on the is_error_noslot_pfn() to
ensure fault->slot is valid, but the only reason that helper is used is because
it was the most efficient code when slot wasn't available. IMO, this would be
better:
if (!slot || kvm_slot_dirty_track_enabled(slot))
return;
if (kvm_is_reserved_pfn(fault->pfn))
return;
On a related topic, a good follow-up to this series would be to pass @fault into
the prefetch helpers, and modify the prefetch logic to re-use fault->slot and
refuse to prefetch across memslot boundaries. That would eliminate all users of
gfn_to_memslot_dirty_bitmap() and allow us to drop that abomination.
