Re: [PATCH 02/11] KVM: arm64: CCA: Introduce Realms
From: Steven Price
Date: Wed Nov 11 2026 - 05:22:21 EST
On 10/11/2026 11:42, Kohei Enju wrote:
> Hi Steve,
Hi Kohei,
> On 11/02 14:12, Steven Price wrote:
>> From: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
>>
>> 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 patch, 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.
>> - Also adjust the memslot preparation checks to reflect the changes.
>>
>> 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.
>>
>> Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
>> Signed-off-by: Steven Price <steven.price@xxxxxxx>
>> ---
>> arch/arm64/include/asm/kvm_emulate.h | 16 +++++++
>> arch/arm64/include/asm/kvm_host.h | 57 +++++++++++++++++-------
>> 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 | 24 ++++++++--
>> arch/arm64/kvm/hyp/include/nvhe/pkvm.h | 2 +-
>> arch/arm64/kvm/hyp/nvhe/switch.c | 4 +-
>> arch/arm64/kvm/hyp/nvhe/timer-sr.c | 2 +-
>> arch/arm64/kvm/mmu.c | 13 +++---
>> arch/arm64/kvm/rmi.c | 18 ++++++++
>> 11 files changed, 169 insertions(+), 31 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 334211b8b2ee..32021bdf2610 100644
>> --- a/arch/arm64/include/asm/kvm_emulate.h
>> +++ b/arch/arm64/include/asm/kvm_emulate.h
>> @@ -831,4 +831,20 @@ 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 ccd2dc8f73c3..7d0222047ca1 100644
>> --- a/arch/arm64/include/asm/kvm_host.h
>> +++ b/arch/arm64/include/asm/kvm_host.h
>> @@ -29,6 +29,7 @@
>> #include <asm/kvm.h>
>> #include <asm/kvm_asm.h>
>> #include <asm/kvm_hcall.h>
>> +#include <asm/kvm_rmi.h>
>> #include <asm/vncr_mapping.h>
>>
>> #define __KVM_HAVE_ARCH_INTC_INITIALIZED
>> @@ -48,6 +49,13 @@
>> #define KVM_VCPU_MAX_FEATURES 10
>> #define KVM_VCPU_VALID_FEATURES (BIT(KVM_VCPU_MAX_FEATURES) - 1)
>>
>> +#define KVM_REALM_VCPU_VALID_FEATURES \
>> + (BIT(KVM_ARM_VCPU_POWER_OFF) | \
>> + BIT(KVM_ARM_VCPU_PSCI_0_2) | \
>> + BIT(KVM_ARM_VCPU_PTRAUTH_ADDRESS) | \
>> + BIT(KVM_ARM_VCPU_SVE) | \
>> + BIT(KVM_ARM_VCPU_PTRAUTH_GENERIC))
>> +
>> #define KVM_REQ_SLEEP \
>> KVM_ARCH_REQ_FLAGS(0, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
>> #define KVM_REQ_IRQ_PENDING KVM_ARCH_REQ(1)
>> @@ -409,6 +417,7 @@ 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
>> };
>>
>> @@ -502,11 +511,14 @@ 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 */
>> @@ -1572,30 +1584,43 @@ struct kvm *kvm_arch_alloc_vm(void);
>>
>> #define __KVM_HAVE_ARCH_FLUSH_REMOTE_TLBS_RANGE
>>
>> -#ifdef __KVM_NVHE_HYPERVISOR__
>> +#define kvm_vm_is_protected(kvm) ((kvm)->arch.vm_flavor >= __VM_PROTECTED)
>>
>> -#define kvm_vm_is_protected(kvm) \
>> - (is_protected_kvm_enabled() && ((kvm)->arch.vm_flavor == VM_PROTECTED_PKVM))
>> +#ifdef __KVM_NVHE_HYPERVISOR__
>> /*
>> * Accessing vcpu->kvm from nVHE hyp stub is tricky, as we need to convert the
>> * pointer to the hyp VA. With pKVM, the nVHE code runs with the hyp_vcpu,
>> - * which is populated correctly and is gated on is_protected_kvm_enabled().
>> + * which is populated correctly. Always vcpu_is_protected_pkvm(), which is
>> + * gated on is_protected_kvm_enabled().
>> + */
>> +#define vcpu_is_protected(vcpu) BUILD_BUG_ON(1)
>> +#else
>> +#define vcpu_is_protected(vcpu) kvm_vm_is_protected((vcpu)->kvm)
>> +#endif
>> +
>> +#define kvm_vm_is_protected_pkvm(kvm) \
>> + (is_protected_kvm_enabled() && ((kvm)->arch.vm_flavor == VM_PROTECTED_PKVM))
>> +
>> +/*
>> + * Rely on is_protected_kvm_enabled() check in kvm_vm_is_protected_pkvm() to
>> + * make sure the vcpu->kvm is always valid VA in the context
>> */
>> -#define vcpu_is_protected(vcpu) \
>> +#define vcpu_is_protected_pkvm(vcpu) \
>> ({ \
>> struct kvm *__kvm = READ_ONCE((vcpu)->kvm); \
>> \
>> - (__kvm && kvm_vm_is_protected(__kvm)); \
>> + (__kvm && kvm_vm_is_protected_pkvm(__kvm)); \
>> })
>
> I've tested the integration branch and found that the secondary CPU
> bring-up fails:
> [ 1.426502] smp: Bringing up secondary CPUs ...
> [ 9.194442] CPU1: failed to come online
> [ 9.194558] CPU1: failed in unknown state : 0x0
> [ 9.197714] smp: Brought up 1 node, 1 CPU
> [ 9.197775] SMP: Total of 1 processors activated.
>
> It seems that this patch missed replacing a use of
> vcpu_is_protected() introduced by the following commit:
>
> 25d726dddc23 ("KVM: arm64: Reject host power-on of a vCPU that EL2 holds powered off")
>
> The following diff fixes the issue for me. Also, though not included in
> the diff, I think vcpu_is_protected() in __pkvm_create_hyp_vcpu() should
> be replaced with vcpu_is_protected_pkvm() as well.
Thanks for the patch - I'll include that in v2.
Thanks,
Steve
> Thanks,
> Kohei
>
> ---8<---
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 522a837637fe..be676c13e219 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -960,7 +960,8 @@ static void __kvm_arm_vcpu_power_off(struct kvm_vcpu *vcpu, u32 mp_state)
> /* The guest's own CPU_OFF: EL2 has already powered the vCPU off. */
> void kvm_arm_vcpu_power_off(struct kvm_vcpu *vcpu)
> {
> - u32 mp_state = vcpu_is_protected(vcpu) ? KVM_MP_STATE_UNINITIALIZED : KVM_MP_STATE_STOPPED;
> + u32 mp_state = vcpu_is_protected_pkvm(vcpu) ?
> + KVM_MP_STATE_UNINITIALIZED : KVM_MP_STATE_STOPPED;
>
> spin_lock(&vcpu->arch.mp_state_lock);
> __kvm_arm_vcpu_power_off(vcpu, mp_state);
> diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c
> index b01f8d44033f..6674e8d6ff4c 100644
> --- a/arch/arm64/kvm/psci.c
> +++ b/arch/arm64/kvm/psci.c
> @@ -68,7 +68,7 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
> * STOPPED before that is the VMM's pause.
> */
> if (!kvm_arm_vcpu_stopped(vcpu) ||
> - (vcpu_is_protected(vcpu) && !kvm_pkvm_vcpu_is_powered_off(vcpu))) {
> + (vcpu_is_protected_pkvm(vcpu) && !kvm_pkvm_vcpu_is_powered_off(vcpu))) {
> if (kvm_psci_version(source_vcpu) != KVM_ARM_PSCI_0_1)
> ret = PSCI_RET_ALREADY_ON;
> else
>