linux-kernel - Re: [PATCH v7 22/45] KVM: arm64: Handle realm VCPU load

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Message-ID: <eb8ea5a0-fe6c-4b96-92da-f9ec0355b4dd@redhat.com>
Date: Tue, 4 Mar 2025 15:15:31 +1000
From: Gavin Shan <gshan@...hat.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>,
 Suzuki K Poulose <suzuki.poulose@....com>, 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>,
 Shanker Donthineni <sdonthineni@...dia.com>, Alper Gun
 <alpergun@...gle.com>, "Aneesh Kumar K . V" <aneesh.kumar@...nel.org>
Subject: Re: [PATCH v7 22/45] KVM: arm64: Handle realm VCPU load

On 2/14/25 2:14 AM, Steven Price wrote:
> When loading a realm VCPU much of the work is handled by the RMM so only
> some of the actions are required. Rearrange kvm_arch_vcpu_load()
> slightly so we can bail out early for a realm guest.
> 
> Signed-off-by: Steven Price <steven.price@....com>
> ---
>   arch/arm64/kvm/arm.c | 12 ++++++++----
>   1 file changed, 8 insertions(+), 4 deletions(-)
> 

One nitpick below:

Reviewed-by: Gavin Shan <gshan@...hat.com>

> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 49ad633c5ca5..3e13e3d87ed9 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -633,10 +633,6 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
>   	kvm_vgic_load(vcpu);
>   	kvm_timer_vcpu_load(vcpu);
>   	kvm_vcpu_load_debug(vcpu);
> -	if (has_vhe())
> -		kvm_vcpu_load_vhe(vcpu);
> -	kvm_arch_vcpu_load_fp(vcpu);
> -	kvm_vcpu_pmu_restore_guest(vcpu);
>   	if (kvm_arm_is_pvtime_enabled(&vcpu->arch))
>   		kvm_make_request(KVM_REQ_RECORD_STEAL, vcpu);
>   
> @@ -659,6 +655,14 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
>   		kvm_call_hyp(__vgic_v3_restore_vmcr_aprs,
>   			     &vcpu->arch.vgic_cpu.vgic_v3);
>   	}

A spare line is needed here.

> +	/* No additional state needs to be loaded on Realmed VMs */
> +	if (vcpu_is_rec(vcpu))
> +		return;
> +
> +	if (has_vhe())
> +		kvm_vcpu_load_vhe(vcpu);
> +	kvm_arch_vcpu_load_fp(vcpu);
> +	kvm_vcpu_pmu_restore_guest(vcpu);
>   
>   	if (!cpumask_test_cpu(cpu, vcpu->kvm->arch.supported_cpus))
>   		vcpu_set_on_unsupported_cpu(vcpu);

Thanks,
Gavin