[PATCH v3 07/36] KVM: arm64: Ignore MMU notifier callbacks for protected VMs

[Fuad Tabba]

On Thu, 5 Mar 2026 at 14:44, Will Deacon <will at kernel.org> wrote:
>
> In preparation for supporting the donation of pinned pages to protected
> VMs, return early from the MMU notifiers when called for a protected VM,
> as the necessary hypercalls are exposed only for non-protected guests.
>
> Signed-off-by: Will Deacon <will at kernel.org>

Reviewed-by: Fuad Tabba <tabba at google.com>

Cheers,
/fuad

> ---
>  arch/arm64/kvm/mmu.c  |  9 ++++++---
>  arch/arm64/kvm/pkvm.c | 19 ++++++++++++++++++-
>  2 files changed, 24 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index ec2eee857208..43632c69adaf 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -340,6 +340,9 @@ static void __unmap_stage2_range(struct kvm_s2_mmu *mmu, phys_addr_t start, u64
>  void kvm_stage2_unmap_range(struct kvm_s2_mmu *mmu, phys_addr_t start,
>                             u64 size, bool may_block)
>  {
> +       if (kvm_vm_is_protected(kvm_s2_mmu_to_kvm(mmu)))
> +               return;
> +
>         __unmap_stage2_range(mmu, start, size, may_block);
>  }
>
> @@ -2219,7 +2222,7 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu)
>
>  bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
>  {
> -       if (!kvm->arch.mmu.pgt)
> +       if (!kvm->arch.mmu.pgt || kvm_vm_is_protected(kvm))
>                 return false;
>
>         __unmap_stage2_range(&kvm->arch.mmu, range->start << PAGE_SHIFT,
> @@ -2234,7 +2237,7 @@ bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
>  {
>         u64 size = (range->end - range->start) << PAGE_SHIFT;
>
> -       if (!kvm->arch.mmu.pgt)
> +       if (!kvm->arch.mmu.pgt || kvm_vm_is_protected(kvm))
>                 return false;
>
>         return KVM_PGT_FN(kvm_pgtable_stage2_test_clear_young)(kvm->arch.mmu.pgt,
> @@ -2250,7 +2253,7 @@ bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
>  {
>         u64 size = (range->end - range->start) << PAGE_SHIFT;
>
> -       if (!kvm->arch.mmu.pgt)
> +       if (!kvm->arch.mmu.pgt || kvm_vm_is_protected(kvm))
>                 return false;
>
>         return KVM_PGT_FN(kvm_pgtable_stage2_test_clear_young)(kvm->arch.mmu.pgt,
> diff --git a/arch/arm64/kvm/pkvm.c b/arch/arm64/kvm/pkvm.c
> index 42f6e50825ac..20d50abb3b94 100644
> --- a/arch/arm64/kvm/pkvm.c
> +++ b/arch/arm64/kvm/pkvm.c
> @@ -407,7 +407,12 @@ int pkvm_pgtable_stage2_map(struct kvm_pgtable *pgt, u64 addr, u64 size,
>
>  int pkvm_pgtable_stage2_unmap(struct kvm_pgtable *pgt, u64 addr, u64 size)
>  {
> -       lockdep_assert_held_write(&kvm_s2_mmu_to_kvm(pgt->mmu)->mmu_lock);
> +       struct kvm *kvm = kvm_s2_mmu_to_kvm(pgt->mmu);
> +
> +       if (WARN_ON(kvm_vm_is_protected(kvm)))
> +               return -EPERM;
> +
> +       lockdep_assert_held_write(&kvm->mmu_lock);
>
>         return __pkvm_pgtable_stage2_unshare(pgt, addr, addr + size);
>  }
> @@ -419,6 +424,9 @@ int pkvm_pgtable_stage2_wrprotect(struct kvm_pgtable *pgt, u64 addr, u64 size)
>         struct pkvm_mapping *mapping;
>         int ret = 0;
>
> +       if (WARN_ON(kvm_vm_is_protected(kvm)))
> +               return -EPERM;
> +
>         lockdep_assert_held(&kvm->mmu_lock);
>         for_each_mapping_in_range_safe(pgt, addr, addr + size, mapping) {
>                 ret = kvm_call_hyp_nvhe(__pkvm_host_wrprotect_guest, handle, mapping->gfn,
> @@ -450,6 +458,9 @@ bool pkvm_pgtable_stage2_test_clear_young(struct kvm_pgtable *pgt, u64 addr, u64
>         struct pkvm_mapping *mapping;
>         bool young = false;
>
> +       if (WARN_ON(kvm_vm_is_protected(kvm)))
> +               return -EPERM;
> +
>         lockdep_assert_held(&kvm->mmu_lock);
>         for_each_mapping_in_range_safe(pgt, addr, addr + size, mapping)
>                 young |= kvm_call_hyp_nvhe(__pkvm_host_test_clear_young_guest, handle, mapping->gfn,
> @@ -461,12 +472,18 @@ bool pkvm_pgtable_stage2_test_clear_young(struct kvm_pgtable *pgt, u64 addr, u64
>  int pkvm_pgtable_stage2_relax_perms(struct kvm_pgtable *pgt, u64 addr, enum kvm_pgtable_prot prot,
>                                     enum kvm_pgtable_walk_flags flags)
>  {
> +       if (WARN_ON(kvm_vm_is_protected(kvm_s2_mmu_to_kvm(pgt->mmu))))
> +               return -EPERM;
> +
>         return kvm_call_hyp_nvhe(__pkvm_host_relax_perms_guest, addr >> PAGE_SHIFT, prot);
>  }
>
>  void pkvm_pgtable_stage2_mkyoung(struct kvm_pgtable *pgt, u64 addr,
>                                  enum kvm_pgtable_walk_flags flags)
>  {
> +       if (WARN_ON(kvm_vm_is_protected(kvm_s2_mmu_to_kvm(pgt->mmu))))
> +               return;
> +
>         WARN_ON(kvm_call_hyp_nvhe(__pkvm_host_mkyoung_guest, addr >> PAGE_SHIFT));
>  }
>
> --
> 2.53.0.473.g4a7958ca14-goog
>