[PATCH 06/11] KVM: arm64: CCA: Add basic infrastructure for creating a realm
Suzuki K Poulose
suzuki.poulose at arm.com
Mon Nov 2 15:49:24 PST 2026
Hi Steven
On 02/11/2026 14:12, Steven Price wrote:
> Introduce the skeleton functions for creating and destroying a realm.
> The IPA size requested is checked against what the RMM supports.
>
> The actual work of constructing the realm will be added in future
> patches.
>
> Signed-off-by: Steven Price <steven.price at arm.com>
> ---
> arch/arm64/include/asm/kvm_rmi.h | 20 ++++++++++++
> arch/arm64/kvm/arm.c | 9 +++++
> arch/arm64/kvm/mmu.c | 18 ++++++++--
> arch/arm64/kvm/rmi.c | 56 ++++++++++++++++++++++++++++++++
> 4 files changed, 101 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_rmi.h b/arch/arm64/include/asm/kvm_rmi.h
> index 3194daaacf2b..f1a1ed6b91f5 100644
> --- a/arch/arm64/include/asm/kvm_rmi.h
> +++ b/arch/arm64/include/asm/kvm_rmi.h
> @@ -6,6 +6,9 @@
> #ifndef __ASM_KVM_RMI_H
> #define __ASM_KVM_RMI_H
>
> +#include <linux/arm-smccc-rmi.h>
> +#include <linux/kvm.h>
> +
> /**
> * enum realm_state - State of a Realm
> *
> @@ -50,12 +53,29 @@ enum realm_state {
> /**
> * struct realm - Additional per VM data for a Realm
> *
> + * @rd: Kernel mapping of the RMM-managed Realm Descriptor (RD) granule
> + * @sro: Preallocated SRO state context for Realm MMU operations
> * @state: The lifetime state machine for the realm
> + * @ia_bits: Number of valid Input Address bits in the IPA
> */
> struct realm {
> + void *rd;
> + /*
> + * Reused by RTT map/unmap SRO commands. Those commands are only
> + * issued from Realm stage-2 map/unmap paths while kvm->mmu_lock is
> + * held for write, including Realm fault handling where
> + * kvm_fault_lock() takes the write side, so concurrent use is
> + * serialized.
> + */
> + struct rmi_sro_state *sro;
> enum realm_state state;
> + unsigned int ia_bits;
> };
>
> void kvm_init_rmi(void);
> +u32 kvm_rmm_ipa_limit(void);
> +
> +int kvm_init_realm(struct kvm *kvm);
> +void kvm_destroy_realm(struct kvm *kvm);
>
> #endif /* __ASM_KVM_RMI_H */
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index c8599fed5902..9a7bbfaf9675 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -303,6 +303,13 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
>
> bitmap_zero(kvm->arch.vcpu_features, KVM_VCPU_MAX_FEATURES);
>
> + /* Initialise the realm bits after the generic bits are enabled */
> + if (kvm_vm_is_realm(kvm)) {
> + ret = kvm_init_realm(kvm);
> + if (ret)
> + goto err_uninit_mmu;
> + }
> +
> return 0;
>
> err_uninit_mmu:
> @@ -367,6 +374,8 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
>
> kvm_destroy_nested(kvm);
> kvm_arm_teardown_hypercalls(kvm);
> + if (kvm_vm_is_realm(kvm))
> + kvm_destroy_realm(kvm);
> }
>
> static bool kvm_has_full_ptr_auth(void)
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 1301c563d705..b049ea67d9af 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -981,10 +981,14 @@ static struct kvm_pgtable_mm_ops kvm_s2_mm_ops = {
>
> static int kvm_init_ipa_range(struct kvm_s2_mmu *mmu, unsigned long type)
> {
> + struct kvm *kvm = kvm_s2_mmu_to_kvm(mmu);
> u32 kvm_ipa_limit = get_kvm_ipa_limit();
> u64 mmfr0, mmfr1;
> u32 phys_shift;
>
> + if (kvm_vm_is_realm(kvm))
> + kvm_ipa_limit = kvm_rmm_ipa_limit();
> +
> phys_shift = KVM_VM_TYPE_ARM_IPA_SIZE(type);
> if (is_protected_kvm_enabled()) {
> phys_shift = kvm_ipa_limit;
> @@ -1034,9 +1038,18 @@ static void stage2_destroy_range(struct kvm_pgtable *pgt, phys_addr_t addr,
>
> static void kvm_stage2_destroy(struct kvm_pgtable *pgt)
> {
> + struct kvm *kvm = kvm_s2_mmu_to_kvm(pgt->mmu);
> unsigned int ia_bits = VTCR_EL2_IPA(pgt->mmu->vtcr);
>
> - stage2_destroy_range(pgt, 0, BIT(ia_bits));
> + /*
> + * Realm RTTs are inaccessible to the host and may contain stale data
> + * after the RMM has released them. The non-root RTTs are explicitly
> + * destroyed through RMI before the RD is destroyed; only the root PGD
> + * pages remain to be freed here.
> + */
> + if (!kvm_vm_is_realm(kvm))
> + stage2_destroy_range(pgt, 0, BIT(ia_bits));
> +
> KVM_PGT_FN(kvm_pgtable_stage2_destroy_pgd)(pgt);
> }
This looks like a good candidate for another callback for vm_s2_ops ?
Something like (incomplete functionally, but this should work).
As a bonus, we can remove two instances of KVM_PGT_FN()
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 5e9c2919c509..96685c52fb6e 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1048,35 +1048,52 @@ static int kvm_init_ipa_range(struct kvm_s2_mmu
*mmu, unsigned long type)
* cond_resched() periodically to prevent hogging the CPU for a long time
* and schedule something else, if required.
*/
-static void stage2_destroy_range(struct kvm_pgtable *pgt, phys_addr_t addr,
- phys_addr_t end)
+static void stage2_destroy_range(struct kvm_pgtable *pgt,
+ void (*pgt_destroy_range_fn)(struct kvm_pgtable *pgt,
+ u64 addr, u64 size))
{
+ u64 addr = 0;
+ u64 end = BIT(VTCR_EL2_IPA(pgt->mmu->vtcr));
u64 next;
do {
next = stage2_range_addr_end(addr, end);
- KVM_PGT_FN(kvm_pgtable_stage2_destroy_range)(pgt, addr,
- next - addr);
+ pgt_destroy_range_fn(pgt, addr, next - addr);
if (next != end)
cond_resched();
} while (addr = next, addr != end);
}
+static void kvm_vm_stage2_destroy(struct kvm_pgtable *pgt)
+{
+ stage2_destroy_range(pgt, kvm_pgtable_stage2_destroy_range);
+ kvm_pgtable_stage2_destroy_pgd(pgt);
+}
+
+static void pkvm_stage2_destroy(struct kvm_pgtable *pgt)
+{
+ stage2_destroy_range(pgt, kvm_pgtable_stage2_destroy_range);
+ pkvm_pgtable_stage2_destroy_pgd(pgt);
+}
+
+/*
+* Realm RTTs are inaccessible to the host and may contain stale data
+* after the RMM has released them. The non-root RTTs are explicitly
+* destroyed through RMI before the RD is destroyed; only the root PGD
+* pages remain to be freed here.
+*/
+static void realm_stage2_destroy(struct kvm_pgtable *pgt,
+ u64 start, u64 end)
+{
+ kvm_pgtable_destroy_pgd(pgt);
+}
+
static void kvm_stage2_destroy(struct kvm_pgtable *pgt)
{
struct kvm *kvm = kvm_s2_mmu_to_kvm(pgt->mmu);
unsigned int ia_bits = VTCR_EL2_IPA(pgt->mmu->vtcr);
- /*
- * Realm RTTs are inaccessible to the host and may contain stale data
- * after the RMM has released them. The non-root RTTs are explicitly
- * destroyed through RMI before the RD is destroyed; only the root PGD
- * pages remain to be freed here.
- */
- if (!kvm_vm_is_realm(kvm))
- stage2_destroy_range(pgt, 0, BIT(ia_bits));
-
- KVM_PGT_FN(kvm_pgtable_stage2_destroy_pgd)(pgt);
+ kvm->arch.vm_s2_ops->stage2_destroy(pgt, 0, BIT(ia_bits));
}
> @@ -1084,6 +1097,8 @@ int kvm_init_stage2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu, unsigned long t
> return -EINVAL;
> }
>
> + mmu->arch = &kvm->arch;
> +
> err = kvm_init_ipa_range(mmu, type);
> if (err)
> return err;
> @@ -1092,7 +1107,6 @@ int kvm_init_stage2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu, unsigned long t
> if (!pgt)
> return -ENOMEM;
>
> - mmu->arch = &kvm->arch;
> err = KVM_PGT_FN(kvm_pgtable_stage2_init)(pgt, mmu, &kvm_s2_mm_ops);
> if (err)
> goto out_free_pgtable;
> diff --git a/arch/arm64/kvm/rmi.c b/arch/arm64/kvm/rmi.c
> index 5b07beff8bc9..45ecbaa467d1 100644
> --- a/arch/arm64/kvm/rmi.c
> +++ b/arch/arm64/kvm/rmi.c
> @@ -6,6 +6,8 @@
> #include <linux/arm-rmi-cmds.h>
> #include <linux/kvm_host.h>
>
> +#include <asm/kvm_emulate.h>
> +#include <asm/kvm_mmu.h>
> #include <asm/kvm_pgtable.h>
> #include <asm/virt.h>
>
> @@ -14,6 +16,60 @@ static bool rmi_has_feature(int reg, unsigned long feature)
> return !!u64_get_bits(rmi_feat_reg(reg), feature);
> }
>
> +u32 kvm_rmm_ipa_limit(void)
> +{
> + return u64_get_bits(rmi_feat_reg(0), RMI_FEATURE_REGISTER_0_S2SZ);
> +}
> +
> +void kvm_destroy_realm(struct kvm *kvm)
> +{
> + struct realm *realm = &kvm->arch.realm;
> + size_t pgd_size = kvm_pgtable_stage2_pgd_size(kvm->arch.mmu.vtcr);
> +
> + if (!kvm_realm_is_created(kvm)) {
> + kfree(realm->sro);
> + realm->sro = NULL;
> + return;
> + }
Do we leak memory of the stage2 PGD if the Realm was never created ?
Should we have something like on top ?
@@ -1646,11 +1645,8 @@ void kvm_destroy_realm(struct kvm *kvm)
guard(mutex)(&kvm->arch.config_lock);
- if (!kvm_realm_is_created(kvm)) {
- kfree(realm->sro);
- realm->sro = NULL;
- return;
- }
+ if (!kvm_realm_is_created(kvm))
+ goto free_pgd;
kvm_set_realm_state(kvm, REALM_STATE_DYING);
@@ -1684,6 +1680,7 @@ void kvm_destroy_realm(struct kvm *kvm)
kvm_set_realm_state(kvm, REALM_STATE_DEAD);
+free_pgd:
/* Now that the realm is destroyed, free the entry-level RTTs. */
kvm_free_stage2_pgd(&kvm->arch.mmu);
Suzuki
> +
> + kvm_set_realm_state(kvm, REALM_STATE_DYING);
> +
> + if (realm->rd) {
> + phys_addr_t rd_phys = virt_to_phys(realm->rd);
> +
> + if (WARN_ON(rmi_realm_terminate(rd_phys, realm->sro)))
> + return;
> +
> + if (WARN_ON(rmi_realm_destroy(rd_phys, realm->sro)))
> + return;
> + rmi_free_delegated_page(rd_phys);
> + realm->rd = NULL;
> + }
> +
> + if (WARN_ON(rmi_undelegate_range(kvm->arch.mmu.pgd_phys,
> + pgd_size)))
> + return;
> +
> + kvm_set_realm_state(kvm, REALM_STATE_DEAD);
> +
> + /* Now that the realm is destroyed, free the entry-level RTTs. */
> + kvm_free_stage2_pgd(&kvm->arch.mmu);
> +
> + kfree(realm->sro);
> + realm->sro = NULL;
> +}
> +
> +int kvm_init_realm(struct kvm *kvm)
> +{
> + struct realm *realm = &kvm->arch.realm;
> +
> + realm->sro = kmalloc_obj(*realm->sro);
> + if (!realm->sro)
> + return -ENOMEM;
> +
> + return 0;
> +}
> +
> static int rmm_check_features(void)
> {
> if (kvm_lpa2_is_enabled() &&
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