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Subject: Re: [PATCH v4 05/21] KVM: arm64: Support SDEI_EVENT_{ENABLE, DISABLE}
 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>
 <20210815001352.81927-6-gshan@redhat.com>
From:   Eric Auger <eauger@redhat.com>
Message-ID: <4ce1aed4-d955-145c-777b-350efec2e7bc@redhat.com>
Date:   Tue, 9 Nov 2021 17:02:09 +0100
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Hi Gavin,

On 8/15/21 2:13 AM, Gavin Shan wrote:
> This supports SDEI_EVENT_{ENABLE, DISABLE} hypercall. After SDEI
> event is registered by guest, it won't be delivered to the guest
> until it's enabled. On the other hand, the SDEI event won't be
> raised to the guest or specific vCPU if it's has been disabled
> on the guest or specific vCPU.
> 
> Signed-off-by: Gavin Shan <gshan@redhat.com>
> ---
>  arch/arm64/kvm/sdei.c | 68 +++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 68 insertions(+)
> 
> diff --git a/arch/arm64/kvm/sdei.c b/arch/arm64/kvm/sdei.c
> index d3ea3eee154b..b022ce0a202b 100644
> --- a/arch/arm64/kvm/sdei.c
> +++ b/arch/arm64/kvm/sdei.c
> @@ -206,6 +206,70 @@ static unsigned long kvm_sdei_hypercall_register(struct kvm_vcpu *vcpu)
>  	return ret;
>  }
>  
> +static unsigned long kvm_sdei_hypercall_enable(struct kvm_vcpu *vcpu,
> +					       bool enable)
> +{
> +	struct kvm *kvm = vcpu->kvm;
> +	struct kvm_sdei_kvm *ksdei = kvm->arch.sdei;
> +	struct kvm_sdei_vcpu *vsdei = vcpu->arch.sdei;
> +	struct kvm_sdei_event *kse = NULL;
> +	struct kvm_sdei_kvm_event *kske = NULL;
> +	unsigned long event_num = smccc_get_arg1(vcpu);
> +	int index = 0;
> +	unsigned long ret = SDEI_SUCCESS;
> +
> +	/* Sanity check */
> +	if (!(ksdei && vsdei)) {
> +		ret = SDEI_NOT_SUPPORTED;
> +		goto out;
> +	}
> +
> +	if (!kvm_sdei_is_valid_event_num(event_num)) {
I would rename into is_exposed_event_num()
> +		ret = SDEI_INVALID_PARAMETERS;
> +		goto out;
> +	}
> +
> +	/* Check if the KVM event exists */
> +	spin_lock(&ksdei->lock);
> +	kske = kvm_sdei_find_kvm_event(kvm, event_num);
> +	if (!kske) {
> +		ret = SDEI_INVALID_PARAMETERS;
should be DENIED according to the spec, ie. nobody registered that event?
> +		goto unlock;
> +	}
> +
> +	/* Check if there is pending events */
does that match the "handler-unregister-pending state" case mentionned
in the spec?
> +	if (kske->state.refcount) {
> +		ret = SDEI_PENDING;
? not documented in my A spec? DENIED?
> +		goto unlock;
> +	}
> +
> +	/* Check if it has been registered */
isn't duplicate of /* Check if the KVM event exists */ ?
> +	kse = kske->kse;
> +	index = (kse->state.type == SDEI_EVENT_TYPE_PRIVATE) ?
> +		vcpu->vcpu_idx : 0;
> +	if (!kvm_sdei_is_registered(kske, index)) {
> +		ret = SDEI_DENIED;
> +		goto unlock;
> +	}
> +
> +	/* Verify its enablement state */
> +	if (enable == kvm_sdei_is_enabled(kske, index)) {
spec says:
Enabling/disabled an event, which is already enabled/disabled, is
permitted and has no effect. I guess ret should be OK.
> +		ret = SDEI_DENIED;
> +		goto unlock;
> +	}
> +
> +	/* Update enablement state */
> +	if (enable)
> +		kvm_sdei_set_enabled(kske, index);
> +	else
> +		kvm_sdei_clear_enabled(kske, index);
> +
> +unlock:
> +	spin_unlock(&ksdei->lock);
> +out:
> +	return ret;
> +}
> +
>  int kvm_sdei_hypercall(struct kvm_vcpu *vcpu)
>  {
>  	u32 func = smccc_get_function(vcpu);
> @@ -220,7 +284,11 @@ int kvm_sdei_hypercall(struct kvm_vcpu *vcpu)
>  		ret = kvm_sdei_hypercall_register(vcpu);
>  		break;
>  	case SDEI_1_0_FN_SDEI_EVENT_ENABLE:
> +		ret = kvm_sdei_hypercall_enable(vcpu, true);
> +		break;
>  	case SDEI_1_0_FN_SDEI_EVENT_DISABLE:
> +		ret = kvm_sdei_hypercall_enable(vcpu, false);
> +		break;
>  	case SDEI_1_0_FN_SDEI_EVENT_CONTEXT:
>  	case SDEI_1_0_FN_SDEI_EVENT_COMPLETE:
>  	case SDEI_1_0_FN_SDEI_EVENT_COMPLETE_AND_RESUME:
> 
Eric