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From:   Eric Auger <eauger@redhat.com>
Subject: Re: [PATCH v4 06/21] KVM: arm64: Support SDEI_EVENT_CONTEXT hypercall
To:     Gavin Shan <gshan@redhat.com>, kvmarm@lists.cs.columbia.edu
Cc:     maz@kernel.org, linux-kernel@vger.kernel.org,
        Jonathan.Cameron@huawei.com, pbonzini@redhat.com, will@kernel.org
References: <20210815001352.81927-1-gshan@redhat.com>
 <20210815001352.81927-7-gshan@redhat.com>
Message-ID: <d9471e38-1840-1f79-c028-8f78afc0d2c7@redhat.com>
Date:   Wed, 10 Nov 2021 12:16:34 +0100
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Hi Gavin,

On 8/15/21 2:13 AM, Gavin Shan wrote:
> This supports SDEI_EVENT_CONTEXT hypercall. It's used by the guest
> to retrieved the original registers (R0 - R17) in its SDEI event
> handler. Those registers can be corrupted during the SDEI event
> delivery.
> 
> Signed-off-by: Gavin Shan <gshan@redhat.com>
> ---
>  arch/arm64/kvm/sdei.c | 40 ++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 40 insertions(+)
> 
> diff --git a/arch/arm64/kvm/sdei.c b/arch/arm64/kvm/sdei.c
> index b022ce0a202b..b4162efda470 100644
> --- a/arch/arm64/kvm/sdei.c
> +++ b/arch/arm64/kvm/sdei.c
> @@ -270,6 +270,44 @@ static unsigned long kvm_sdei_hypercall_enable(struct kvm_vcpu *vcpu,
>  	return ret;
>  }
>  
> +static unsigned long kvm_sdei_hypercall_context(struct kvm_vcpu *vcpu)
> +{
> +	struct kvm *kvm = vcpu->kvm;
> +	struct kvm_sdei_kvm *ksdei = kvm->arch.sdei;
> +	struct kvm_sdei_vcpu *vsdei = vcpu->arch.sdei;
> +	struct kvm_sdei_vcpu_regs *regs;
> +	unsigned long index = smccc_get_arg1(vcpu);
s/index/param_id to match the spec?
> +	unsigned long ret = SDEI_SUCCESS;
> +
> +	/* Sanity check */
> +	if (!(ksdei && vsdei)) {
> +		ret = SDEI_NOT_SUPPORTED;
> +		goto out;
> +	}
> +
> +	if (index > ARRAY_SIZE(vsdei->state.critical_regs.regs)) {
> +		ret = SDEI_INVALID_PARAMETERS;
> +		goto out;
> +	}
I would move the above after regs = and use regs there (although the
regs ARRAY_SIZE of both is identifical)
> +
> +	/* Check if the pending event exists */
> +	spin_lock(&vsdei->lock);
> +	if (!(vsdei->critical_event || vsdei->normal_event)) {
> +		ret = SDEI_DENIED;
> +		goto unlock;
> +	}
> +
> +	/* Fetch the requested register */
> +	regs = vsdei->critical_event ? &vsdei->state.critical_regs :
> +				       &vsdei->state.normal_regs;
> +	ret = regs->regs[index];
> +
> +unlock:
> +	spin_unlock(&vsdei->lock);
> +out:
> +	return ret;
> +}
> +
>  int kvm_sdei_hypercall(struct kvm_vcpu *vcpu)
>  {
>  	u32 func = smccc_get_function(vcpu);
> @@ -290,6 +328,8 @@ int kvm_sdei_hypercall(struct kvm_vcpu *vcpu)
>  		ret = kvm_sdei_hypercall_enable(vcpu, false);
>  		break;
>  	case SDEI_1_0_FN_SDEI_EVENT_CONTEXT:
> +		ret = kvm_sdei_hypercall_context(vcpu);
> +		break;
>  	case SDEI_1_0_FN_SDEI_EVENT_COMPLETE:
>  	case SDEI_1_0_FN_SDEI_EVENT_COMPLETE_AND_RESUME:
>  	case SDEI_1_0_FN_SDEI_EVENT_UNREGISTER:
> 
Eric