[PATCH v2 11/18] KVM: arm64: Add a shrinker for pKVM

[Fuad Tabba]

On Mon, 6 Jul 2026 at 18:54, Vincent Donnefort <vdonnefort at google.com> wrote:
>
> Integrate the pKVM memory reclaim interface with the host's memory
> management subsystem.
>
> This allows the host to automatically recover unused memory fom the
> hypervisor's heap allocator when the host is under memory pressure.
>
> Signed-off-by: Vincent Donnefort <vdonnefort at google.com>
>
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 50adfff75be8..3dc2b9d2c322 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -122,6 +122,8 @@ static bool vgic_present, kvm_arm_initialised;
>
>  static DEFINE_PER_CPU(unsigned char, kvm_hyp_initialized);
>
> +static struct shrinker *pkvm_shrinker;
> +
>  bool is_kvm_arm_initialised(void)
>  {
>         return kvm_arm_initialised;
> @@ -2526,8 +2528,8 @@ static void __init teardown_hyp_mode(void)
>                 }
>
>                 free_pages(kvm_nvhe_sym(kvm_arm_hyp_percpu_base)[cpu], nvhe_percpu_order());
> -
>         }
> +       shrinker_free(pkvm_shrinker);
>  }
>
>  static int __init do_pkvm_init(u32 hyp_va_bits)
> @@ -2713,6 +2715,18 @@ static void pkvm_hyp_init_ptrauth(void)
>         }
>  }
>
> +static unsigned long
> +pkvm_shrinker_count(struct shrinker *shrink, struct shrink_control *sc)
> +{
> +       return pkvm_hyp_reclaimable(PKVM_TOPUP_HYP_ALLOC) ?: SHRINK_EMPTY;
> +}
> +
> +static unsigned long
> +pkvm_shrinker_scan(struct shrinker *shrink, struct shrink_control *sc)
> +{
> +       return pkvm_hyp_reclaim(PKVM_TOPUP_HYP_ALLOC, sc->nr_to_scan);
> +}
> +
>  /* Inits Hyp-mode on all online CPUs */
>  static int __init init_hyp_mode(void)
>  {
> @@ -2883,6 +2897,16 @@ static int __init init_hyp_mode(void)
>                         kvm_err("Failed to init hyp memory protection\n");
>                         goto out_err;
>                 }
> +
> +               pkvm_shrinker = shrinker_alloc(0, "pkvm");
> +               if (pkvm_shrinker) {
> +                       pkvm_shrinker->count_objects = pkvm_shrinker_count;
> +                       pkvm_shrinker->scan_objects = pkvm_shrinker_scan;
> +                       shrinker_register(pkvm_shrinker);
> +               } else {
> +                       kvm_err("Failed to register shrinker for pKVM\n");
> +               }
> +
>         }

Sashiko might be onto something here. The shrinker goes live in
init_hyp_mode(), but kvm_protected_mode_initialized isn't set until
finalize_pkvm()...

Cheers,
/fuad

>
>         return 0;
> --
> 2.55.0.rc2.803.g1fd1e6609c-goog
>