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Message-ID: <CABpDEumQ=62nZ_xEN6oMHw=J+6ps=Gy=1vx8i=6Hz+BacO1Ymg@mail.gmail.com>
Date: Fri, 23 Jan 2026 10:57:38 -0800
From: Alper Gun <alpergun@...gle.com>
To: Steven Price <steven.price@....com>
Cc: kvm@...r.kernel.org, kvmarm@...ts.linux.dev,
Catalin Marinas <catalin.marinas@....com>, Marc Zyngier <maz@...nel.org>, Will Deacon <will@...nel.org>,
James Morse <james.morse@....com>, Oliver Upton <oliver.upton@...ux.dev>,
Suzuki K Poulose <suzuki.poulose@....com>, Zenghui Yu <yuzenghui@...wei.com>,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
Joey Gouly <joey.gouly@....com>, Alexandru Elisei <alexandru.elisei@....com>,
Christoffer Dall <christoffer.dall@....com>, Fuad Tabba <tabba@...gle.com>, linux-coco@...ts.linux.dev,
Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>, Gavin Shan <gshan@...hat.com>,
Shanker Donthineni <sdonthineni@...dia.com>, "Aneesh Kumar K . V" <aneesh.kumar@...nel.org>,
Emi Kisanuki <fj0570is@...itsu.com>, Vishal Annapurve <vannapurve@...gle.com>
Subject: Re: [PATCH v12 22/46] arm64: RMI: Create the realm descriptor
On Wed, Dec 17, 2025 at 2:13 AM Steven Price <steven.price@....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@....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
>
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