[PATCH v14 14/44] arm64: RMI: Basic infrastructure for creating a realm.
Steven Price
steven.price at arm.com
Wed May 13 06:17:22 PDT 2026
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>
---
Changes since v13:
* Rebased and updated to RMM-v2.0-bet1.
* Auxiliary granules have been removed in RMM-v2.0-bet1
Changes since v12:
* Drop the RMM_PAGE_{SHIFT,SIZE} defines - the RMM is now configured to
be the same as the host's page size.
* Rework delegate/undelegate functions to use the new RMI range based
operations.
Changes since v11:
* Major rework to drop the realm configuration and make the
construction of realms implicit rather than driven by the VMM
directly.
* The code to create RDs, handle VMIDs etc is moved to later patches.
Changes since v10:
* Rename from RME to RMI.
* Move the stage2 cleanup to a later patch.
Changes since v9:
* Avoid walking the stage 2 page tables when destroying the realm -
the real ones are not accessible to the non-secure world, and the RMM
may leave junk in the physical pages when returning them.
* Fix an error path in realm_create_rd() to actually return an error value.
Changes since v8:
* Fix free_delegated_granule() to not call kvm_account_pgtable_pages();
a separate wrapper will be introduced in a later patch to deal with
RTTs.
* Minor code cleanups following review.
Changes since v7:
* Minor code cleanup following Gavin's review.
Changes since v6:
* Separate RMM RTT calculations from host PAGE_SIZE. This allows the
host page size to be larger than 4k while still communicating with an
RMM which uses 4k granules.
Changes since v5:
* Introduce free_delegated_granule() to replace many
undelegate/free_page() instances and centralise the comment on
leaking when the undelegate fails.
* Several other minor improvements suggested by reviews - thanks for
the feedback!
Changes since v2:
* Improved commit description.
* Improved return failures for rmi_check_version().
* Clear contents of PGD after it has been undelegated in case the RMM
left stale data.
* Minor changes to reflect changes in previous patches.
---
arch/arm64/include/asm/kvm_emulate.h | 29 ++++++++++++++
arch/arm64/include/asm/kvm_rmi.h | 51 +++++++++++++++++++++++++
arch/arm64/kvm/arm.c | 12 ++++++
arch/arm64/kvm/mmu.c | 12 +++++-
arch/arm64/kvm/rmi.c | 57 ++++++++++++++++++++++++++++
5 files changed, 159 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index 5bf3d7e1d92c..82fd777bd9bb 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -688,4 +688,33 @@ static inline void vcpu_set_hcrx(struct kvm_vcpu *vcpu)
vcpu->arch.hcrx_el2 |= HCRX_EL2_EnASR;
}
}
+
+static inline bool kvm_is_realm(struct kvm *kvm)
+{
+ if (static_branch_unlikely(&kvm_rmi_is_available))
+ return kvm->arch.is_realm;
+ return false;
+}
+
+static inline enum realm_state kvm_realm_state(struct kvm *kvm)
+{
+ return READ_ONCE(kvm->arch.realm.state);
+}
+
+static inline void kvm_set_realm_state(struct kvm *kvm,
+ enum realm_state new_state)
+{
+ WRITE_ONCE(kvm->arch.realm.state, new_state);
+}
+
+static inline bool kvm_realm_is_created(struct kvm *kvm)
+{
+ return kvm_is_realm(kvm) && kvm_realm_state(kvm) != REALM_STATE_NONE;
+}
+
+static inline bool vcpu_is_rec(const struct kvm_vcpu *vcpu)
+{
+ return false;
+}
+
#endif /* __ARM64_KVM_EMULATE_H__ */
diff --git a/arch/arm64/include/asm/kvm_rmi.h b/arch/arm64/include/asm/kvm_rmi.h
index 4936007947fd..9de34983ee52 100644
--- a/arch/arm64/include/asm/kvm_rmi.h
+++ b/arch/arm64/include/asm/kvm_rmi.h
@@ -6,12 +6,63 @@
#ifndef __ASM_KVM_RMI_H
#define __ASM_KVM_RMI_H
+#include <asm/rmi_smc.h>
+
+/**
+ * enum realm_state - State of a Realm
+ */
+enum realm_state {
+ /**
+ * @REALM_STATE_NONE:
+ * Realm has not yet been created. rmi_realm_create() has not
+ * yet been called.
+ */
+ REALM_STATE_NONE,
+ /**
+ * @REALM_STATE_NEW:
+ * Realm is under construction, rmi_realm_create() has been
+ * called, but it is not yet activated. Pages may be populated.
+ */
+ REALM_STATE_NEW,
+ /**
+ * @REALM_STATE_ACTIVE:
+ * Realm has been created and is eligible for execution with
+ * rmi_rec_enter(). Pages may no longer be populated with
+ * rmi_data_create().
+ */
+ REALM_STATE_ACTIVE,
+ /**
+ * @REALM_STATE_DYING:
+ * Realm is in the process of being destroyed or has already been
+ * destroyed.
+ */
+ REALM_STATE_DYING,
+ /**
+ * @REALM_STATE_DEAD:
+ * Realm has been destroyed.
+ */
+ REALM_STATE_DEAD
+};
+
/**
* struct realm - Additional per VM data for a Realm
+ *
+ * @state: The lifetime state machine for the realm
+ * @rd: Kernel mapping of the Realm Descriptor (RD)
+ * @params: Parameters for the RMI_REALM_CREATE command
+ * @ia_bits: Number of valid Input Address bits in the IPA
*/
struct realm {
+ enum realm_state state;
+ void *rd;
+ struct realm_params *params;
+ unsigned int ia_bits;
};
void kvm_init_rmi(void);
+u32 kvm_realm_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 247e03b33035..18251e561524 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -264,6 +264,13 @@ 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_is_realm(kvm)) {
+ ret = kvm_init_realm(kvm);
+ if (ret)
+ goto err_uninit_mmu;
+ }
+
return 0;
err_uninit_mmu:
@@ -326,6 +333,8 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
kvm_unshare_hyp(kvm, kvm + 1);
kvm_arm_teardown_hypercalls(kvm);
+ if (kvm_is_realm(kvm))
+ kvm_destroy_realm(kvm);
}
static bool kvm_has_full_ptr_auth(void)
@@ -486,6 +495,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
else
r = kvm_supports_cacheable_pfnmap();
break;
+ case KVM_CAP_ARM_RMI:
+ r = static_key_enabled(&kvm_rmi_is_available);
+ break;
default:
r = 0;
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index d089c107d9b7..ba8286472286 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -877,10 +877,14 @@ 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_is_realm(kvm))
+ kvm_ipa_limit = kvm_realm_ipa_limit();
+
phys_shift = KVM_VM_TYPE_ARM_IPA_SIZE(type);
if (is_protected_kvm_enabled()) {
phys_shift = kvm_ipa_limit;
@@ -974,6 +978,8 @@ 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;
@@ -982,7 +988,6 @@ 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;
@@ -1114,7 +1119,10 @@ void kvm_free_stage2_pgd(struct kvm_s2_mmu *mmu)
write_unlock(&kvm->mmu_lock);
if (pgt) {
- kvm_stage2_destroy(pgt);
+ if (!kvm_is_realm(kvm))
+ kvm_stage2_destroy(pgt);
+ else
+ kvm_pgtable_stage2_destroy_pgd(pgt);
kfree(pgt);
}
}
diff --git a/arch/arm64/kvm/rmi.c b/arch/arm64/kvm/rmi.c
index 6e28b669ded2..f51ec667445e 100644
--- a/arch/arm64/kvm/rmi.c
+++ b/arch/arm64/kvm/rmi.c
@@ -5,6 +5,8 @@
#include <linux/kvm_host.h>
+#include <asm/kvm_emulate.h>
+#include <asm/kvm_mmu.h>
#include <asm/kvm_pgtable.h>
#include <asm/rmi_cmds.h>
#include <asm/virt.h>
@@ -14,6 +16,61 @@ static bool rmi_has_feature(unsigned long feature)
return !!u64_get_bits(rmm_feat_reg0, feature);
}
+u32 kvm_realm_ipa_limit(void)
+{
+ return u64_get_bits(rmm_feat_reg0, 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 (realm->params) {
+ free_page((unsigned long)realm->params);
+ realm->params = NULL;
+ }
+
+ if (!kvm_realm_is_created(kvm))
+ return;
+
+ kvm_set_realm_state(kvm, REALM_STATE_DYING);
+
+ write_lock(&kvm->mmu_lock);
+ kvm_stage2_unmap_range(&kvm->arch.mmu, 0,
+ BIT(realm->ia_bits - 1), true);
+ write_unlock(&kvm->mmu_lock);
+
+ if (realm->rd) {
+ phys_addr_t rd_phys = virt_to_phys(realm->rd);
+
+ if (WARN_ON(rmi_realm_terminate(rd_phys)))
+ return;
+
+ if (WARN_ON(rmi_realm_destroy(rd_phys)))
+ return;
+ 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);
+}
+
+int kvm_init_realm(struct kvm *kvm)
+{
+ kvm->arch.realm.params = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT);
+
+ if (!kvm->arch.realm.params)
+ return -ENOMEM;
+ return 0;
+}
+
static int rmm_check_features(void)
{
if (kvm_lpa2_is_enabled() && !rmi_has_feature(RMI_FEATURE_REGISTER_0_LPA2)) {
--
2.43.0
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