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

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Date:   Thu, 27 Jan 2022 15:13:43 +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 1/12/22 3:54 AM, Gavin Shan wrote:
> Hi Eric,
> 
> On 11/10/21 2:47 AM, Eric Auger wrote:
>> 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.
> 
> Yep, you're right. I didn't figure out it. I may put a comment here.
> For now, the SDEI client driver in the guest kernel doesn't attempt
> to change the routing mode.
> 
>     /* FIXME: The affinity should be verified */
> 
>>> +
>>> +    /* 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.
> 
> They're equivalent as the handler is provided as a parameter when
> the event is 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?
> 
> @refcount here indicates pending SDEI event for delivery. In this case,
> chaning its routing mode is disallowed.
OK. I guess you will document the refcount role somewhere.

Thanks

Eric
> 
>>> +        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:
>>>
> 
> Thanks,
> Gavin
>