Subject: Re: [PATCH v14 32/44] KVM: arm64: Handle Realm PSCI requests

From: Gavin Shan <[email-masked]>
Date: Thu, 28 May 2026 16:55:06 +1000

Hi Steve,

On 5/13/26 11:17 PM, Steven Price wrote:
> The RMM needs to be informed of the target REC when a PSCI call is made
> with an MPIDR argument.
> 
> This requirement will be removed in a future release of the RMM 2.0
> specification but is still required for v2.0-bet1.
> 
> Co-developed-by: Suzuki K Poulose <[email-masked]>
> Signed-off-by: Suzuki K Poulose <[email-masked]>
> Signed-off-by: Steven Price <[email-masked]>
> ---
> Chanegs since v13:
>   * The ioctl KVM_ARM_VCPU_RMI_PSCI_COMPLETE has gone. The RMI call is
>     made automatically just before entering the REC again.
> 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/psci.c            | 15 ++++++++-
>   arch/arm64/kvm/rmi.c             | 58 ++++++++++++++++++++++++++++++++
>   3 files changed, 75 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_rmi.h b/arch/arm64/include/asm/kvm_rmi.h
> index b65cfec10dee..eacf82a7467d 100644
> --- a/arch/arm64/include/asm/kvm_rmi.h
> +++ b/arch/arm64/include/asm/kvm_rmi.h
> @@ -109,6 +109,9 @@ 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/psci.c b/arch/arm64/kvm/psci.c
> index 3b5dbe9a0a0e..a2cd55dc7b5b 100644
> --- a/arch/arm64/kvm/psci.c
> +++ b/arch/arm64/kvm/psci.c
> @@ -103,7 +103,6 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
>   
>   	reset_state->reset = true;
>   	kvm_make_request(KVM_REQ_VCPU_RESET, vcpu);
> -

This change isn't supposed to be part of this patch :-)

>   	/*
>   	 * Make sure the reset request is observed if the RUNNABLE mp_state is
>   	 * observed.
> @@ -142,6 +141,20 @@ 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;
> +
> +		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 761b38a4071c..2b03e962ee41 100644
> --- a/arch/arm64/kvm/rmi.c
> +++ b/arch/arm64/kvm/rmi.c
> @@ -3,6 +3,7 @@
>    * Copyright (C) 2023-2025 ARM Ltd.
>    */
>   
> +#include <uapi/linux/psci.h>
>   #include <linux/kvm_host.h>
>   
>   #include <asm/kvm_emulate.h>
> @@ -127,6 +128,25 @@ 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;
> +
> +	/*
> +	 * XXX: RMM-v2.0 doesn't require the target REC address for completing
> +	 * PSCI requests. Temporary hack until RMM implementation catches up
> +	 * to the full spec.
> +	 */
> +	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 -ENXIO;

> +
> +	return 0;
> +}
> +
>   static int realm_rtt_create(struct realm *realm,
>   			    unsigned long addr,
>   			    int level,
> @@ -1004,6 +1024,41 @@ static void kvm_complete_ripas_change(struct kvm_vcpu *vcpu)
>   	rec->run->exit.ripas_base = base;
>   }
>   
> +static void kvm_rec_complete_psci(struct kvm_vcpu *vcpu)
> +{
> +	struct rec_run *run = vcpu->arch.rec.run;
> +	unsigned long status = PSCI_RET_DENIED;
> +	unsigned long ret = vcpu_get_reg(vcpu, 0);
> +	struct kvm_vcpu *target;
> +
> +	switch (run->exit.gprs[0]) {
> +	/*
> +	 * XXX: RMM-v2.0 doesn't cause RMI_EXIT_PSCI for AFFINITY_INFO
> +	 * Temporary hack until tf-RMM gets the REC to MPIDR mapping via
> +	 * RD Auxiliary granules.
> +	 * For now always report SUCCESS
> +	 */
> +	case PSCI_0_2_FN64_AFFINITY_INFO:
> +		status = PSCI_RET_SUCCESS;
> +		break;
> +	case PSCI_0_2_FN64_CPU_ON: {
> +		if (ret != PSCI_RET_SUCCESS &&
> +		    ret != PSCI_RET_ALREADY_ON)
> +			status = PSCI_RET_DENIED;
> +		else
> +			status = PSCI_RET_SUCCESS;
> +		break;
> +	}
> +	default:
> +		return;
> +	}
> +
> +	target = kvm_mpidr_to_vcpu(vcpu->kvm, run->exit.gprs[1]);
> +	/* RMM makes sure that we don't get RMI_EXIT_PSCI for invalid mpidrs */
> +	if (target)
> +		realm_psci_complete(vcpu, target, status);
> +}
> +
>   /*
>    * kvm_rec_pre_enter - Complete operations before entering a REC
>    *
> @@ -1028,6 +1083,9 @@ int kvm_rec_pre_enter(struct kvm_vcpu *vcpu)
>   		for (int i = 0; i < REC_RUN_GPRS; i++)
>   			rec->run->enter.gprs[i] = vcpu_get_reg(vcpu, i);
>   		break;
> +	case RMI_EXIT_PSCI:
> +		kvm_rec_complete_psci(vcpu);
> +		break;
>   	case RMI_EXIT_RIPAS_CHANGE:
>   		kvm_complete_ripas_change(vcpu);
>   		break;

Thanks,
Gavin