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

Fuad Tabba
2026-03-11T12:50:40Z

On Thu, 5 Mar 2026 at 14:44, Will Deacon <will@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@kernel.org>

Reviewed-by: Fuad Tabba <tabba@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
>