[PATCH v12 22/46] arm64: RMI: Create the realm descriptor

[Alper Gun]

On Wed, Dec 17, 2025 at 2:13 AM Steven Price <steven.price at arm.com> wrote:
>
> Creating a realm involves first creating a realm descriptor (RD). This
> involves passing the configuration information to the RMM. Do this as
> part of realm_ensure_created() so that the realm is created when it is
> first needed.
>
> Signed-off-by: Steven Price <steven.price at arm.com>
> ---
> New patch for v12
> ---
>  arch/arm64/kvm/rmi.c | 117 ++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 115 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/kvm/rmi.c b/arch/arm64/kvm/rmi.c
> index b51e68e56d56..18edc7eeb5fa 100644
> --- a/arch/arm64/kvm/rmi.c
> +++ b/arch/arm64/kvm/rmi.c
> @@ -500,6 +500,106 @@ static void realm_unmap_shared_range(struct kvm *kvm,
>                              start, end);
>  }
>
> +/* Calculate the number of s2 root rtts needed */
> +static int realm_num_root_rtts(struct realm *realm)
> +{
> +       unsigned int ipa_bits = realm->ia_bits;
> +       unsigned int levels = 4 - get_start_level(realm);
> +       unsigned int sl_ipa_bits = levels * (RMM_PAGE_SHIFT - 3) +
> +                                  RMM_PAGE_SHIFT;
> +
> +       if (sl_ipa_bits >= ipa_bits)
> +               return 1;
> +
> +       return 1 << (ipa_bits - sl_ipa_bits);
> +}
> +
> +static int realm_create_rd(struct kvm *kvm)
> +{
> +       struct realm *realm = &kvm->arch.realm;
> +       struct realm_params *params = realm->params;
> +       void *rd = NULL;
> +       phys_addr_t rd_phys, params_phys;
> +       size_t pgd_size = kvm_pgtable_stage2_pgd_size(kvm->arch.mmu.vtcr);
> +       int i, r;
> +       int rtt_num_start;
> +
> +       realm->ia_bits = VTCR_EL2_IPA(kvm->arch.mmu.vtcr);
> +       rtt_num_start = realm_num_root_rtts(realm);
> +
> +       if (WARN_ON(realm->rd || !realm->params))
> +               return -EEXIST;
> +
> +       if (pgd_size / RMM_PAGE_SIZE < rtt_num_start)
> +               return -EINVAL;
> +
> +       rd = (void *)__get_free_page(GFP_KERNEL);
> +       if (!rd)
> +               return -ENOMEM;
> +
> +       rd_phys = virt_to_phys(rd);
> +       if (rmi_granule_delegate(rd_phys)) {
> +               r = -ENXIO;
> +               goto free_rd;
> +       }
> +
> +       for (i = 0; i < pgd_size; i += RMM_PAGE_SIZE) {
> +               phys_addr_t pgd_phys = kvm->arch.mmu.pgd_phys + i;
> +
> +               if (rmi_granule_delegate(pgd_phys)) {
> +                       r = -ENXIO;
> +                       goto out_undelegate_tables;
> +               }
> +       }
> +
> +       params->s2sz = VTCR_EL2_IPA(kvm->arch.mmu.vtcr);
> +       params->rtt_level_start = get_start_level(realm);
> +       params->rtt_num_start = rtt_num_start;
> +       params->rtt_base = kvm->arch.mmu.pgd_phys;
> +       params->vmid = realm->vmid;

I don't see a way to configure rpv and hash_algo anymore. I assume they
are gone for a minimal userspace interface. Will there be a way to set
them going forward?

> +
> +       params_phys = virt_to_phys(params);
> +
> +       if (rmi_realm_create(rd_phys, params_phys)) {
> +               r = -ENXIO;
> +               goto out_undelegate_tables;
> +       }
> +
> +       if (WARN_ON(rmi_rec_aux_count(rd_phys, &realm->num_aux))) {
> +               WARN_ON(rmi_realm_destroy(rd_phys));
> +               r = -ENXIO;
> +               goto out_undelegate_tables;
> +       }
> +
> +       realm->rd = rd;
> +       WRITE_ONCE(realm->state, REALM_STATE_NEW);
> +       /* The realm is up, free the parameters.  */
> +       free_page((unsigned long)realm->params);
> +       realm->params = NULL;
> +
> +       return 0;
> +
> +out_undelegate_tables:
> +       while (i > 0) {
> +               i -= RMM_PAGE_SIZE;
> +
> +               phys_addr_t pgd_phys = kvm->arch.mmu.pgd_phys + i;
> +
> +               if (WARN_ON(rmi_granule_undelegate(pgd_phys))) {
> +                       /* Leak the pages if they cannot be returned */
> +                       kvm->arch.mmu.pgt = NULL;
> +                       break;
> +               }
> +       }
> +       if (WARN_ON(rmi_granule_undelegate(rd_phys))) {
> +               /* Leak the page if it isn't returned */
> +               return r;
> +       }
> +free_rd:
> +       free_page((unsigned long)rd);
> +       return r;
> +}
> +
>  static int realm_unmap_private_page(struct realm *realm,
>                                     unsigned long ipa,
>                                     unsigned long *next_addr)
> @@ -803,8 +903,21 @@ static int realm_init_ipa_state(struct kvm *kvm,
>
>  static int realm_ensure_created(struct kvm *kvm)
>  {
> -       /* Provided in later patch */
> -       return -ENXIO;
> +       int ret;
> +
> +       switch (kvm_realm_state(kvm)) {
> +       case REALM_STATE_NONE:
> +               break;
> +       case REALM_STATE_NEW:
> +               return 0;
> +       case REALM_STATE_DEAD:
> +               return -ENXIO;
> +       default:
> +               return -EBUSY;
> +       }
> +
> +       ret = realm_create_rd(kvm);
> +       return ret;
>  }
>
>  static int set_ripas_of_protected_regions(struct kvm *kvm)
> --
> 2.43.0
>