linux-kernel - Re: [PATCH v4 10/21] KVM: arm64: Support SDEI_EVENT_ROUTING

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Date:   Tue, 9 Nov 2021 19:47:50 +0100
From:   Eric Auger <eauger@...hat.com>
To:     Gavin Shan <gshan@...hat.com>, kvmarm@...ts.cs.columbia.edu
Cc:     maz@...nel.org, linux-kernel@...r.kernel.org,
        Jonathan.Cameron@...wei.com, pbonzini@...hat.com, will@...nel.org
Subject: Re: [PATCH v4 10/21] KVM: arm64: Support SDEI_EVENT_ROUTING_SET
 hypercall

Hi Gavin,
On 8/15/21 2:13 AM, Gavin Shan wrote:
> This supports SDEI_EVENT_ROUTING_SET hypercall. It's used by the
> guest to set route mode and affinity for the registered KVM event.
> It's only valid for the shared events. It's not allowed to do so
> when the corresponding event has been raised to the guest.
> 
> Signed-off-by: Gavin Shan <gshan@...hat.com>
> ---
>  arch/arm64/kvm/sdei.c | 64 +++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 64 insertions(+)
> 
> diff --git a/arch/arm64/kvm/sdei.c b/arch/arm64/kvm/sdei.c
> index 5dfa74b093f1..458695c2394f 100644
> --- a/arch/arm64/kvm/sdei.c
> +++ b/arch/arm64/kvm/sdei.c
> @@ -489,6 +489,68 @@ static unsigned long kvm_sdei_hypercall_info(struct kvm_vcpu *vcpu)
>  	return ret;
>  }
>  
> +static unsigned long kvm_sdei_hypercall_route(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_event *kse = NULL;
> +	struct kvm_sdei_kvm_event *kske = NULL;
> +	unsigned long event_num = smccc_get_arg1(vcpu);
> +	unsigned long route_mode = smccc_get_arg2(vcpu);
> +	unsigned long route_affinity = smccc_get_arg3(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)) {
> +		ret = SDEI_INVALID_PARAMETERS;
> +		goto out;
> +	}
> +
> +	if (!(route_mode == SDEI_EVENT_REGISTER_RM_ANY ||
> +	      route_mode == SDEI_EVENT_REGISTER_RM_PE)) {
> +		ret = SDEI_INVALID_PARAMETERS;
> +		goto out;
> +	}
Some sanity checking on the affinity arg could be made as well according
to 5.1.2  affinity desc. The fn shall return INVALID_PARAMETER in case
of invalid affinity.
> +
> +	/* Check if the KVM event has been registered */
> +	spin_lock(&ksdei->lock);
> +	kske = kvm_sdei_find_kvm_event(kvm, event_num);
> +	if (!kske) {
> +		ret = SDEI_INVALID_PARAMETERS;
> +		goto unlock;
> +	}
> +
> +	/* Validate KVM event state */
> +	kse = kske->kse;
> +	if (kse->state.type != SDEI_EVENT_TYPE_SHARED) {
> +		ret = SDEI_INVALID_PARAMETERS;
> +		goto unlock;
> +	}
> +
Event handler is in a state other than: handler-registered.
> +	if (!kvm_sdei_is_registered(kske, index) ||
> +	    kvm_sdei_is_enabled(kske, index)     ||
> +	    kske->state.refcount) {
I am not sure about the refcount role here. Does it make sure the state
is != handler-enabled and running or handler-unregister-pending?

I think we would gain in readibility if we had a helper to check whether
we are in those states?
> +		ret = SDEI_DENIED;
> +		goto unlock;
> +	}
> +
> +	/* Update state */
> +	kske->state.route_mode     = route_mode;
> +	kske->state.route_affinity = route_affinity;
> +
> +unlock:
> +	spin_unlock(&ksdei->lock);
> +out:
> +	return ret;
> +}
> +
>  int kvm_sdei_hypercall(struct kvm_vcpu *vcpu)
>  {
>  	u32 func = smccc_get_function(vcpu);
> @@ -523,6 +585,8 @@ int kvm_sdei_hypercall(struct kvm_vcpu *vcpu)
>  		ret = kvm_sdei_hypercall_info(vcpu);
>  		break;
>  	case SDEI_1_0_FN_SDEI_EVENT_ROUTING_SET:
> +		ret = kvm_sdei_hypercall_route(vcpu);
> +		break;
>  	case SDEI_1_0_FN_SDEI_PE_MASK:
>  	case SDEI_1_0_FN_SDEI_PE_UNMASK:
>  	case SDEI_1_0_FN_SDEI_INTERRUPT_BIND:
> 
Eric