Re: [PATCH v4 07/21] KVM: arm64: Support SDEI_EVENT_UNREGISTER hypercall

Gavin Shan
2022-01-12T02:39:18Z

Hi Eric,

On 11/10/21 1:05 AM, Eric Auger wrote:
> On 8/15/21 2:13 AM, Gavin Shan wrote:
>> This supports SDEI_EVENT_UNREGISTER hypercall. It's used by the
>> guest to unregister SDEI event. The SDEI event won't be raised to
>> the guest or specific vCPU after it's unregistered successfully.
>> It's notable the SDEI event is disabled automatically on the guest
>> or specific vCPU once it's unregistered successfully.
>>
>> Signed-off-by: Gavin Shan <gshan@redhat.com>
>> ---
>> arch/arm64/kvm/sdei.c | 61 +++++++++++++++++++++++++++++++++++++++++++
>> 1 file changed, 61 insertions(+)
>>
>> diff --git a/arch/arm64/kvm/sdei.c b/arch/arm64/kvm/sdei.c
>> index b4162efda470..a3ba69dc91cb 100644
>> --- a/arch/arm64/kvm/sdei.c
>> +++ b/arch/arm64/kvm/sdei.c
>> @@ -308,6 +308,65 @@ static unsigned long kvm_sdei_hypercall_context(struct kvm_vcpu *vcpu)
>> return ret;
>> }
>>
>> +static unsigned long kvm_sdei_hypercall_unregister(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);
>> + 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;
>> + }
>> +
>> + /* 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;
>> + goto unlock;
>> + }
>> +
>> + /* Check if there is pending events */
>> + if (kske->state.refcount) {
>> + ret = SDEI_PENDING;
> don't you want to record the fact the unregistration is outstanding to
> perform subsequent actions? Otherwise nothing will hapen when the
> current executing handlers complete?

It's not necessary. The guest should retry in this case.

>> + goto unlock;
>> + }
>> +
>> + /* Check if it has been registered */
>> + kse = kske->kse;
>> + index = (kse->state.type == SDEI_EVENT_TYPE_PRIVATE) ?
>> + vcpu->vcpu_idx : 0;
> you could have an inline for the above as this is executed in many
> functions. even including the code below.

Ok, it's a good idea.

>> + if (!kvm_sdei_is_registered(kske, index)) {
>> + ret = SDEI_DENIED;
>> + goto unlock;
>> + }
>> +
>> + /* The event is disabled when it's unregistered */
>> + kvm_sdei_clear_enabled(kske, index);
>> + kvm_sdei_clear_registered(kske, index);
>> + if (kvm_sdei_empty_registered(kske)) {
> a refcount mechanism would be cleaner I think.

A refcount isn't working well. We need a mapping here because the private
SDEI event can be enabled/registered on multiple vCPUs. We need to know
the exact vCPUs where the private SDEI event is enabled/registered.

>> + list_del(&kske->link);
>> + kfree(kske);
>> + }
>> +
>> +unlock:
>> + spin_unlock(&ksdei->lock);
>> +out:
>> + return ret;
>> +}
>> +
>> int kvm_sdei_hypercall(struct kvm_vcpu *vcpu)
>> {
>> u32 func = smccc_get_function(vcpu);
>> @@ -333,6 +392,8 @@ int kvm_sdei_hypercall(struct kvm_vcpu *vcpu)
>> case SDEI_1_0_FN_SDEI_EVENT_COMPLETE:
>> case SDEI_1_0_FN_SDEI_EVENT_COMPLETE_AND_RESUME:
>> case SDEI_1_0_FN_SDEI_EVENT_UNREGISTER:
>> + ret = kvm_sdei_hypercall_unregister(vcpu);
>> + break;
>> case SDEI_1_0_FN_SDEI_EVENT_STATUS:
>> case SDEI_1_0_FN_SDEI_EVENT_GET_INFO:
>> case SDEI_1_0_FN_SDEI_EVENT_ROUTING_SET:
>>

Thanks,
Gavin