Re: [PATCH v13 30/48] KVM: arm64: Handle Realm PSCI requests

Suzuki K Poulose
2026-03-30T10:36:18Z

On 18/03/2026 15:53, Steven Price wrote:
> The RMM needs to be informed of the target REC when a PSCI call is made
> with an MPIDR argument. Expose an ioctl to the userspace in case the PSCI
> is handled by it.
>
> [NOTE: A future version of the RMM specification is likely to remove the
> need for this ioctl.]

This will need to stay for the PSCI_CPU_ON case, where the host has to
acknowledge the onlining of a vCPU.

>
> Co-developed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> Signed-off-by: Steven Price <steven.price@arm.com>

For the record, we can drop the UAPI following our discussions and
implicitly do the PSCI complete before REC_ENTER, similar to what
we do for the SET_RIPAS request. The VMM/KVM can treat the case
as a normal PSCI_CPU_ON request and return the result as in normal
VMs.

The target REC may ENTER before we complete the reporting, but we can
handle this error case (RMI_ERROR_REC) and return -EAGAIN to the
userspace.

Suzuki

> ---
> Changes since v12:
> * Chance return code for non-realms to -ENXIO to better represent that
> the ioctl is invalid for non-realms (checkpatch is insistent that
> "ENOSYS means 'invalid syscall nr' and nothing else").
> Changes since v11:
> * RMM->RMI renaming.
> Changes since v6:
> * Use vcpu_is_rec() rather than kvm_is_realm(vcpu->kvm).
> * Minor renaming/formatting fixes.
> ---
> arch/arm64/include/asm/kvm_rmi.h | 3 +++
> arch/arm64/kvm/arm.c | 25 +++++++++++++++++++++++++
> arch/arm64/kvm/psci.c | 30 ++++++++++++++++++++++++++++++
> arch/arm64/kvm/rmi.c | 14 ++++++++++++++
> 4 files changed, 72 insertions(+)
>
> diff --git a/arch/arm64/include/asm/kvm_rmi.h b/arch/arm64/include/asm/kvm_rmi.h
> index 38208be3c602..1ee5ed0f5ab2 100644
> --- a/arch/arm64/include/asm/kvm_rmi.h
> +++ b/arch/arm64/include/asm/kvm_rmi.h
> @@ -117,6 +117,9 @@ int realm_map_non_secure(struct realm *realm,
> unsigned long size,
> enum kvm_pgtable_prot prot,
> struct kvm_mmu_memory_cache *memcache);
> +int realm_psci_complete(struct kvm_vcpu *source,
> + struct kvm_vcpu *target,
> + unsigned long status);
>
> static inline bool kvm_realm_is_private_address(struct realm *realm,
> unsigned long addr)
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 304fb1f2b3ff..61182eb0cf70 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -1846,6 +1846,22 @@ static int kvm_arm_vcpu_set_events(struct kvm_vcpu *vcpu,
> return __kvm_arm_vcpu_set_events(vcpu, events);
> }
>
> +static int kvm_arm_vcpu_rmi_psci_complete(struct kvm_vcpu *vcpu,
> + struct kvm_arm_rmi_psci_complete *arg)
> +{
> + struct kvm_vcpu *target = kvm_mpidr_to_vcpu(vcpu->kvm, arg->target_mpidr);
> +
> + if (!target)
> + return -EINVAL;
> +
> + /*
> + * RMM v1.0 only supports PSCI_RET_SUCCESS or PSCI_RET_DENIED
> + * for the status. But, let us leave it to the RMM to filter
> + * for making this future proof.
> + */
> + return realm_psci_complete(vcpu, target, arg->psci_status);
> +}
> +
> long kvm_arch_vcpu_ioctl(struct file *filp,
> unsigned int ioctl, unsigned long arg)
> {
> @@ -1974,6 +1990,15 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
>
> return kvm_arm_vcpu_finalize(vcpu, what);
> }
> + case KVM_ARM_VCPU_RMI_PSCI_COMPLETE: {
> + struct kvm_arm_rmi_psci_complete req;
> +
> + if (!vcpu_is_rec(vcpu))
> + return -ENXIO;
> + if (copy_from_user(&req, argp, sizeof(req)))
> + return -EFAULT;
> + return kvm_arm_vcpu_rmi_psci_complete(vcpu, &req);
> + }
> default:
> r = -EINVAL;
> }
> diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c
> index 3b5dbe9a0a0e..a68f3c1878a5 100644
> --- a/arch/arm64/kvm/psci.c
> +++ b/arch/arm64/kvm/psci.c
> @@ -103,6 +103,12 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
>
> reset_state->reset = true;
> kvm_make_request(KVM_REQ_VCPU_RESET, vcpu);
> + /*
> + * Make sure we issue PSCI_COMPLETE before the VCPU can be
> + * scheduled.
> + */
> + if (vcpu_is_rec(vcpu))
> + realm_psci_complete(source_vcpu, vcpu, PSCI_RET_SUCCESS);
>
> /*
> * Make sure the reset request is observed if the RUNNABLE mp_state is
> @@ -115,6 +121,11 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
>
> out_unlock:
> spin_unlock(&vcpu->arch.mp_state_lock);
> + if (vcpu_is_rec(vcpu) && ret != PSCI_RET_SUCCESS) {
> + realm_psci_complete(source_vcpu, vcpu,
> + ret == PSCI_RET_ALREADY_ON ?
> + PSCI_RET_SUCCESS : PSCI_RET_DENIED);
> + }
> return ret;
> }
>
> @@ -142,6 +153,25 @@ static unsigned long kvm_psci_vcpu_affinity_info(struct kvm_vcpu *vcpu)
> /* Ignore other bits of target affinity */
> target_affinity &= target_affinity_mask;
>
> + if (vcpu_is_rec(vcpu)) {
> + struct kvm_vcpu *target_vcpu;
> +
> + /* RMM supports only zero affinity level */
> + if (lowest_affinity_level != 0)
> + return PSCI_RET_INVALID_PARAMS;
> +
> + target_vcpu = kvm_mpidr_to_vcpu(kvm, target_affinity);
> + if (!target_vcpu)
> + return PSCI_RET_INVALID_PARAMS;
> +
> + /*
> + * Provide the references of the source and target RECs to the
> + * RMM so that the RMM can complete the PSCI request.
> + */
> + realm_psci_complete(vcpu, target_vcpu, PSCI_RET_SUCCESS);
> + return PSCI_RET_SUCCESS;
> + }
> +
> /*
> * If one or more VCPU matching target affinity are running
> * then ON else OFF
> diff --git a/arch/arm64/kvm/rmi.c b/arch/arm64/kvm/rmi.c
> index 30292814b1ec..e56c8af2ad61 100644
> --- a/arch/arm64/kvm/rmi.c
> +++ b/arch/arm64/kvm/rmi.c
> @@ -353,6 +353,20 @@ static void free_rtt(phys_addr_t phys)
> kvm_account_pgtable_pages(phys_to_virt(phys), -1);
> }
>
> +int realm_psci_complete(struct kvm_vcpu *source, struct kvm_vcpu *target,
> + unsigned long status)
> +{
> + int ret;
> +
> + ret = rmi_psci_complete(virt_to_phys(source->arch.rec.rec_page),
> + virt_to_phys(target->arch.rec.rec_page),
> + status);
> + if (ret)
> + return -EINVAL;
> +
> + return 0;
> +}
> +
> static int realm_rtt_create(struct realm *realm,
> unsigned long addr,
> int level,