[PATCH v22 18/23] KVM: arm64: CCA: Introduce Realms
Suzuki K Poulose
suzuki.poulose at arm.com
Mon Oct 5 22:10:53 PDT 2026
On 06/10/2026 04:42, Gavin Shan wrote:
> On 10/5/26 7:07 PM, Suzuki K Poulose wrote:
>> From: Steven Price <steven.price at arm.com>
>>
>> Add foundational work for supporting Realms.
>> - Add a new VM flavor.
>> - At KVM init, check if the KVM can support Realms (though not
>> functional
>> yet) and will be advertised by static key kvm_rmi_is_available. This
>> will be turned on in a later patches, once we have all the bits and
>> pieces ready. For now check if we are blessed with KVM_MODE_RMM.
>> - Add realm specific tracking in kvm_arch. Since Realm and protected
>> pKVM
>> states are mutually exclusive, move them into a union.
>>
>> Please note that we cannot create Realm VMs yet. This requires further
>> changes to the UABI and core RMI driver support, which will come later.
>>
>> Reviewed-by: Jonathan Cameron <jonathan.cameron at oss.qualcomm.com>
>> Signed-off-by: Steven Price <steven.price at arm.com>
>> Co-developed-by: Suzuki K Poulose <suzuki.poulose at arm.com>
>> Signed-off-by: Suzuki K Poulose <suzuki.poulose at arm.com>
>> ---
>> arch/arm64/include/asm/kvm_emulate.h | 16 ++++++++
>> arch/arm64/include/asm/kvm_host.h | 19 ++++++---
>> arch/arm64/include/asm/kvm_rmi.h | 61 ++++++++++++++++++++++++++++
>> arch/arm64/include/asm/virt.h | 1 +
>> arch/arm64/kvm/Makefile | 2 +-
>> arch/arm64/kvm/arm.c | 6 +++
>> arch/arm64/kvm/mmu.c | 1 +
>> arch/arm64/kvm/rmi.c | 18 ++++++++
>> 8 files changed, 118 insertions(+), 6 deletions(-)
>> create mode 100644 arch/arm64/include/asm/kvm_rmi.h
>> create mode 100644 arch/arm64/kvm/rmi.c
>>
>> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/
>> include/asm/kvm_emulate.h
>> index a3c1928bdf743..d360a8b05b8bf 100644
>> --- a/arch/arm64/include/asm/kvm_emulate.h
>> +++ b/arch/arm64/include/asm/kvm_emulate.h
>> @@ -793,4 +793,20 @@ static inline void kvm_reset_vcpu_psci(struct
>> kvm_vcpu *vcpu,
>> vcpu_set_reg(vcpu, 0, reset_state->r0);
>> }
>> +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_vm_is_realm(kvm) && kvm_realm_state(kvm) !=
>> REALM_STATE_NONE;
>> +}
>> +
>> #endif /* __ARM64_KVM_EMULATE_H__ */
>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/
>> asm/kvm_host.h
>> index dfa9d4ec61a76..3debffef638a4 100644
>> --- a/arch/arm64/include/asm/kvm_host.h
>> +++ b/arch/arm64/include/asm/kvm_host.h
>> @@ -27,6 +27,7 @@
>> #include <asm/fpsimd.h>
>> #include <asm/kvm.h>
>> #include <asm/kvm_asm.h>
>> +#include <asm/kvm_rmi.h>
>> #include <asm/vncr_mapping.h>
>> #define __KVM_HAVE_ARCH_INTC_INITIALIZED
>> @@ -334,6 +335,7 @@ enum kvm_arm_vm_flavor {
>> VM_PKVM, /* Normal guests on pKVM */
>> MARKER(__VM_PROTECTED),
>> VM_PROTECTED_PKVM, /* Protected VM */
>> + VM_REALM, /* CCA */
>> VM_FLAVOR_MAX
>> };
>> @@ -450,11 +452,14 @@ struct kvm_arch {
>> /* Count the number of VNCR_EL2 TLBs */
>> atomic_t vncr_tlb_count;
>> - /*
>> - * For an untrusted host VM, 'pkvm.handle' is used to lookup
>> - * the associated pKVM instance in the hypervisor.
>> - */
>> - struct kvm_protected_vm pkvm;
>> + union {
>> + /*
>> + * For an untrusted host VM, 'pkvm.handle' is used to lookup
>> + * the associated pKVM instance in the hypervisor.
>> + */
>> + struct kvm_protected_vm pkvm;
>> + struct realm realm;
>> + };
>> #ifdef CONFIG_PTDUMP_STAGE2_DEBUGFS
>> /* Nested virtualization info */
>> @@ -1565,6 +1570,10 @@ struct kvm *kvm_arch_alloc_vm(void);
>> (__kvm && kvm_vm_is_protected_pkvm(__kvm)); \
>> })
>> +
>> +#define kvm_vm_is_realm(kvm) ((kvm)->arch.vm_flavor == VM_REALM)
>> +#define vcpu_is_rec(vcpu) kvm_vm_is_realm((vcpu)->kvm)
>> +
>
> vcpu_is_rec() isn't safely called in nVHE hyp stub. So do we need add
> something
> similiar to what we had for vcpu_is_protected(vcpu) in PATCH[05]?
>
> #ifdef __KVM_NVHE_HYPERVISOR__
> /* vcpu_is_rec() isn't expected to called in nVHE hyp stub */
> #define vcpu_is_rec(vcpu) BUILD_BUG_ON(1)
> #else
> #define vcpu_is_rec(vcpu) kvm_vm_is_realm((vcpu)->kvm)
> #endif
>
>
>> #define kvm_vm_hyp_is_distrusting(kvm) ((kvm)->arch.vm_flavor >=
>> __VM_DISTRUSTING_HYP)
>> int kvm_arm_vcpu_finalize(struct kvm_vcpu *vcpu, int feature);
>> diff --git a/arch/arm64/include/asm/kvm_rmi.h b/arch/arm64/include/
>> asm/kvm_rmi.h
>> new file mode 100644
>> index 0000000000000..44f5c75a27b5b
>> --- /dev/null
>> +++ b/arch/arm64/include/asm/kvm_rmi.h
>> @@ -0,0 +1,61 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +/*
>> + * Copyright (C) 2023-2026 ARM Ltd.
>> + */
>> +
>> +#ifndef __ASM_KVM_RMI_H
>> +#define __ASM_KVM_RMI_H
>> +
>> +/**
>> + * enum realm_state - State of a Realm
>> + *
>> + * Mirrors the RMM's Realm lifecycle states where they are meaningful
>> to KVM,
>> + * with REALM_STATE_DYING being a KVM-internal state used to prevent
>> further
>> + * requests while teardown is in progress. KVM does not track
>> REALM_SYSTEM_OFF
>> + * or REALM_ZOMBIE separately as they naturally lead to teardown.
>> + */
>> +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.
> ^^^^^
> Granule instead of page is the term applicable to RMM. Lets use a generic
> term 'memory' here. Also, lets mention the name of the function used to
> populate the memory (granules), which is consistent to the comments for
> REALM_STATE_ACTIVE.
>
> Memory may be populated by rmi_rtt_data_map_init().
>
>
>> + */
>> + 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,
>
> rmi_data_create() is an invalid function name.
>
> Memory can't longer be populated using rmi_rtt_data_map_init().
Ack, thanks for spotting, I will fix them.
Cheers
Suzuki
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