linux-kernel - Re: [PATCH v4 05/21] KVM: arm64: Support SDEI_EVENT

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Date:   Wed, 12 Jan 2022 10:29:08 +0800
From:   Gavin Shan <gshan@...hat.com>
To:     Eric Auger <eauger@...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 05/21] KVM: arm64: Support SDEI_EVENT_{ENABLE, DISABLE}
 hypercall

Hi Eric,

On 11/10/21 12:02 AM, Eric Auger wrote:
> 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@...hat.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()

kvm_sdei_is_virtual() has been recommended by you when you reviewed the following
patch. I think kvm_sdei_is_virtual() is good enough :)

    [PATCH v4 02/21] KVM: arm64: Add SDEI virtualization infrastructure

>> +		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?

Ok.

>> +		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?

Yep, It should be DENIED.

>> +		goto unlock;
>> +	}
>> +
>> +	/* Check if it has been registered */
> isn't duplicate of /* Check if the KVM event exists */ ?

It's not duplicate check, but the comment here seems misleading. I will
correct this to:

	/* Check if it has been defined or exposed */

>> +	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.

yep, it 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:
>>

Thanks,
Gavin