Subject: Re: [PATCH v14 20/44] arm64: RMI: Support for the VGIC in realms

From: Gavin Shan <[email-masked]>
Date: Thu, 28 May 2026 14:07:27 +1000

Hi Steve,

On 5/13/26 11:17 PM, Steven Price wrote:
> The RMM provides emulation of a VGIC to the realm guest. With RMM v2.0
> the registers are passed in the system registers so this works similar
> to a normal guest, but kvm_arch_vcpu_put() need reordering to early out,
> and realm guests don't support GICv2 even if the host does.
> 
> Signed-off-by: Steven Price <[email-masked]>
> ---
> Changes from v12:
>   * GIC registers are now passed in the system registers rather than via
>     rec_entry/rec_exit which removes most of the changes.
> Changes from v11:
>   * Minor changes to align with the previous patches. Note that the VGIC
>     handling will change with RMM v2.0.
> Changes from v10:
>   * Make sure we sync the VGIC v4 state, and only populate valid lrs from
>     the list.
> Changes from v9:
>   * Copy gicv3_vmcr from the RMM at the same time as gicv3_hcr rather
>     than having to handle that as a special case.
> Changes from v8:
>   * Propagate gicv3_hcr to from the RMM.
> Changes from v5:
>   * Handle RMM providing fewer GIC LRs than the hardware supports.
> ---
>   arch/arm64/kvm/arm.c            | 11 ++++++++---
>   arch/arm64/kvm/vgic/vgic-init.c |  2 +-
>   2 files changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 93d34762db91..21d9dfdb1ea0 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -786,19 +786,24 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
>   		kvm_call_hyp_nvhe(__pkvm_vcpu_put);
>   	}
>   
> +	kvm_timer_vcpu_put(vcpu);
> +	kvm_vgic_put(vcpu);
> +
> +	vcpu->cpu = -1;
> +
> +	if (vcpu_is_rec(vcpu))
> +		return;
> +

For a REC, kvm_vcpu_{load, put}_debug() becomes unbalanced in kvm_arch_vcpu_{load, put}().
kvm_vcpu_load_debug() is called in kvm_arch_vcpu_load(), but kvm_vcpu_put_debug() won't
be called in kvm_arch_vcpu_put() after this whole series is applied.

>   	kvm_vcpu_put_debug(vcpu);
>   	kvm_arch_vcpu_put_fp(vcpu);
>   	if (has_vhe())
>   		kvm_vcpu_put_vhe(vcpu);
> -	kvm_timer_vcpu_put(vcpu);
> -	kvm_vgic_put(vcpu);
>   	kvm_vcpu_pmu_restore_host(vcpu);
>   	if (vcpu_has_nv(vcpu))
>   		kvm_vcpu_put_hw_mmu(vcpu);
>   	kvm_arm_vmid_clear_active();
>   
>   	vcpu_clear_on_unsupported_cpu(vcpu);
> -	vcpu->cpu = -1;
>   }
>   
>   static void __kvm_arm_vcpu_power_off(struct kvm_vcpu *vcpu)
> diff --git a/arch/arm64/kvm/vgic/vgic-init.c b/arch/arm64/kvm/vgic/vgic-init.c
> index 933983bb2005..a9db963dfd23 100644
> --- a/arch/arm64/kvm/vgic/vgic-init.c
> +++ b/arch/arm64/kvm/vgic/vgic-init.c
> @@ -81,7 +81,7 @@ int kvm_vgic_create(struct kvm *kvm, u32 type)
>   	 * the proper checks already.
>   	 */
>   	if (type == KVM_DEV_TYPE_ARM_VGIC_V2 &&
> -		!kvm_vgic_global_state.can_emulate_gicv2)
> +	    (!kvm_vgic_global_state.can_emulate_gicv2 || kvm_is_realm(kvm)))
>   		return -ENODEV;
>   
>   	/*

Thanks,
Gavin