linux-kernel - Re: [PATCH v9 13/43] arm64: RME: Support for the VGIC in realms

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Message-ID: <45ae476d-a557-40a5-81d2-99841fda4941@arm.com>
Date: Thu, 3 Jul 2025 14:22:43 +0100
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Steven Price <steven.price@....com>, kvm@...r.kernel.org,
 kvmarm@...ts.linux.dev
Cc: Catalin Marinas <catalin.marinas@....com>, Marc Zyngier <maz@...nel.org>,
 Will Deacon <will@...nel.org>, James Morse <james.morse@....com>,
 Oliver Upton <oliver.upton@...ux.dev>, Zenghui Yu <yuzenghui@...wei.com>,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 Joey Gouly <joey.gouly@....com>, Alexandru Elisei
 <alexandru.elisei@....com>, Christoffer Dall <christoffer.dall@....com>,
 Fuad Tabba <tabba@...gle.com>, linux-coco@...ts.linux.dev,
 Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>,
 Gavin Shan <gshan@...hat.com>, Shanker Donthineni <sdonthineni@...dia.com>,
 Alper Gun <alpergun@...gle.com>, "Aneesh Kumar K . V"
 <aneesh.kumar@...nel.org>, Emi Kisanuki <fj0570is@...itsu.com>
Subject: Re: [PATCH v9 13/43] arm64: RME: Support for the VGIC in realms

On 11/06/2025 11:48, Steven Price wrote:
> The RMM provides emulation of a VGIC to the realm guest but delegates
> much of the handling to the host. Implement support in KVM for
> saving/restoring state to/from the REC structure.
> 
> Signed-off-by: Steven Price <steven.price@....com>
> ---
> 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/include/asm/kvm_rme.h |  1 +
>   arch/arm64/kvm/arm.c             | 16 +++++++++--
>   arch/arm64/kvm/rme.c             |  5 ++++
>   arch/arm64/kvm/vgic/vgic-init.c  |  2 +-
>   arch/arm64/kvm/vgic/vgic-v3.c    |  6 +++-
>   arch/arm64/kvm/vgic/vgic.c       | 49 ++++++++++++++++++++++++++++++--
>   6 files changed, 72 insertions(+), 7 deletions(-)
> 

...

> diff --git a/arch/arm64/kvm/vgic/vgic-init.c b/arch/arm64/kvm/vgic/vgic-init.c
> index eb1205654ac8..77b4962ebfb6 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;
>   
>   	/*
> diff --git a/arch/arm64/kvm/vgic/vgic-v3.c b/arch/arm64/kvm/vgic/vgic-v3.c
> index b9ad7c42c5b0..c10ad817030d 100644
> --- a/arch/arm64/kvm/vgic/vgic-v3.c
> +++ b/arch/arm64/kvm/vgic/vgic-v3.c
> @@ -8,9 +8,11 @@
>   #include <linux/kvm_host.h>
>   #include <linux/string_choices.h>
>   #include <kvm/arm_vgic.h>
> +#include <asm/kvm_emulate.h>
>   #include <asm/kvm_hyp.h>
>   #include <asm/kvm_mmu.h>
>   #include <asm/kvm_asm.h>
> +#include <asm/rmi_smc.h>
>   
>   #include "vgic.h"
>   
> @@ -758,7 +760,9 @@ void vgic_v3_put(struct kvm_vcpu *vcpu)
>   		return;
>   	}
>   
> -	if (likely(!is_protected_kvm_enabled()))
> +	if (vcpu_is_rec(vcpu))
> +		cpu_if->vgic_vmcr = vcpu->arch.rec.run->exit.gicv3_vmcr;
> +	else if (likely(!is_protected_kvm_enabled()))

This function is never reached for Realms, this should be folded in 
vgic_rmm_save_state(). See below.


>   		kvm_call_hyp(__vgic_v3_save_vmcr_aprs, cpu_if);
>   	WARN_ON(vgic_v4_put(vcpu));
>   
> diff --git a/arch/arm64/kvm/vgic/vgic.c b/arch/arm64/kvm/vgic/vgic.c
> index c7aed48c5668..2908b4610c4e 100644
> --- a/arch/arm64/kvm/vgic/vgic.c
> +++ b/arch/arm64/kvm/vgic/vgic.c

...

>   void kvm_vgic_put(struct kvm_vcpu *vcpu)
>   {
> -	if (unlikely(!irqchip_in_kernel(vcpu->kvm) || !vgic_initialized(vcpu->kvm))) {
> +	if (unlikely(vcpu_is_rec(vcpu)))
> +		return;

^^^

> +	if (unlikely(!irqchip_in_kernel(vcpu->kvm) ||
> +		     !vgic_initialized(vcpu->kvm))) {
>   		if (has_vhe() && static_branch_unlikely(&kvm_vgic_global_state.gicv3_cpuif))
>   			__vgic_v3_deactivate_traps(&vcpu->arch.vgic_cpu.vgic_v3);
>   		return;

Suzuki