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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>
 <4ce1aed4-d955-145c-777b-350efec2e7bc@redhat.com>
 <d7fdb8f8-d0f7-32c4-9644-0ab7cb46dfdf@redhat.com>
From:   Eric Auger <eauger@redhat.com>
Message-ID: <69cdc2b8-ccbe-dbe2-4805-04f1a53d9a53@redhat.com>
Date:   Tue, 25 Jan 2022 19:23:40 +0100
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Hi Gavin,

On 1/12/22 3:29 AM, Gavin Shan wrote:
> 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@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()
> 
> kvm_sdei_is_virtual() has been recommended by you when you reviewed the
> following
> patch. I think kvm_sdei_is_virtual() is good enough :)

argh, is_virtual() then :)

Eric
> 
>    [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
>