On Fri, Mar 10, 2023 at 04:22:56PM -0800, Sean Christopherson wrote:
...
> +int kvm_write_track_add_gfn(struct kvm *kvm, gfn_t gfn)
> +{
> + struct kvm_memory_slot *slot;
> + int idx;
> +
> + idx = srcu_read_lock(&kvm->srcu);
> +
> + slot = gfn_to_memslot(kvm, gfn);
> + if (!slot) {
> + srcu_read_unlock(&kvm->srcu, idx);
> + return -EINVAL;
> + }
> +
Also fail if slot->flags & KVM_MEMSLOT_INVALID is true?
There should exist a window for external users to see an invalid slot
when a slot is about to get deleted/moved.
(It happens before MOVE is rejected in kvm_arch_prepare_memory_region()).
> + write_lock(&kvm->mmu_lock);
> + __kvm_write_track_add_gfn(kvm, slot, gfn);
> + write_unlock(&kvm->mmu_lock);
> +
> + srcu_read_unlock(&kvm->srcu, idx);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(kvm_write_track_add_gfn);
> +
> +/*
> + * remove the guest page from the tracking pool which stops the interception
> + * of corresponding access on that page.
> + *
> + * @kvm: the guest instance we are interested in.
> + * @gfn: the guest page.
> + */
> +int kvm_write_track_remove_gfn(struct kvm *kvm, gfn_t gfn)
> +{
> + struct kvm_memory_slot *slot;
> + int idx;
> +
> + idx = srcu_read_lock(&kvm->srcu);
> +
> + slot = gfn_to_memslot(kvm, gfn);
> + if (!slot) {
> + srcu_read_unlock(&kvm->srcu, idx);
> + return -EINVAL;
> + }
> +
Ditto.
> + write_lock(&kvm->mmu_lock);
> + __kvm_write_track_remove_gfn(kvm, slot, gfn);
> + write_unlock(&kvm->mmu_lock);
> +
> + srcu_read_unlock(&kvm->srcu, idx);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(kvm_write_track_remove_gfn);
