Re: [PATCH v13 26/48] arm64: RMI: Create the realm descriptor

Steven Price
2026-03-20T16:41:19Z

On 19/03/2026 18:25, Wei-Lin Chang wrote:
> On Wed, Mar 18, 2026 at 03:53:50PM +0000, Steven Price 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@arm.com>
>> ---
>> Changes since v12:
>> * Since RMM page size is now equal to the host's page size various
>> calculations are simplified.
>> * Switch to using range based APIs to delegate/undelegate.
>> * VMID handling is now handled entirely by the RMM.
>> ---
>> arch/arm64/kvm/rmi.c | 94 +++++++++++++++++++++++++++++++++++++++++++-
>> 1 file changed, 92 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm64/kvm/rmi.c b/arch/arm64/kvm/rmi.c
>> index 38349c7b34f4..d5fee203824b 100644
>> --- a/arch/arm64/kvm/rmi.c
>> +++ b/arch/arm64/kvm/rmi.c
>> @@ -649,6 +649,83 @@ static void realm_unmap_shared_range(struct kvm *kvm,
>> start, end);
>> }
>>
>> +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;
>> +
>> + realm->ia_bits = VTCR_EL2_IPA(kvm->arch.mmu.vtcr);
>> +
>> + if (WARN_ON(realm->rd || !realm->params))
>> + return -EEXIST;
>> +
>> + rd = (void *)__get_free_page(GFP_KERNEL);
>
> Hi,
>
> Should this be GFP_KERNEL_ACCOUNT?

Yes that would be better.

>> + if (!rd)
>> + return -ENOMEM;
>> +
>> + rd_phys = virt_to_phys(rd);
>> + if (delegate_page(rd_phys)) {
>> + r = -ENXIO;
>> + goto free_rd;
>> + }
>> +
>> + if (delegate_range(kvm->arch.mmu.pgd_phys, pgd_size)) {
>> + 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 = pgd_size / PAGE_SIZE;
>> + params->rtt_base = kvm->arch.mmu.pgd_phys;
>> +
>> + if (kvm->arch.arm_pmu) {
>> + params->pmu_num_ctrs = kvm->arch.nr_pmu_counters;
>> + params->flags |= RMI_REALM_PARAM_FLAG_PMU;
>> + }
>> +
>> + if (kvm_lpa2_is_enabled())
>> + params->flags |= RMI_REALM_PARAM_FLAG_LPA2;
>> +
>> + 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:
>> + if (WARN_ON(undelegate_range(kvm->arch.mmu.pgd_phys, i))) {
>> + /* Leak the pages if they cannot be returned */
>> + kvm->arch.mmu.pgt = NULL;
>
> Did you mean kvm->arch.mmu.pgd_phys = NULL; ?

No, although I agree this isn't exactly ideal. kvm_free_stage2_pgd()
uses mmu->pgt to decide whether to free the memory - pgd_phys isn't used
in that path. Technically here we end up leaking more than just the PGD
pages in this case, but as it's a "should never happen" case I didn't
see the need to worry about the leak being a bit larger than necessary.

Thanks,
Steve

> Thanks,
> Wei-Lin Chang
>
>> + }
>> + if (WARN_ON(undelegate_page(rd_phys))) {
>> + /* Leak the page if it isn't returned */
>> + return r;
>> + }
>> +free_rd:
>> + free_page((unsigned long)rd);
>> + return r;
>> +}
>> +
>> static void realm_unmap_private_range(struct kvm *kvm,
>> unsigned long start,
>> unsigned long end,
>> @@ -893,8 +970,21 @@ 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
>>