Re: [PATCH v7 3/4] s390: ap: implement PAPQ AQIC interception in kernel

Pierre Morel
2019-04-30T08:18:32Z

On 29/04/2019 18:50, Halil Pasic wrote:
> On Fri, 26 Apr 2019 15:01:27 +0200
> Pierre Morel <pmorel@linux.ibm.com> wrote:
>
>> +static struct ap_queue_status vfio_ap_setirq(struct vfio_ap_queue *q)
>> +{
>> + struct ap_qirq_ctrl aqic_gisa = {};
>> + struct ap_queue_status status = {};
>> + struct kvm_s390_gisa *gisa;
>> + struct kvm *kvm;
>> + unsigned long h_nib, h_pfn;
>> + int ret;
>> +
>> + q->a_pfn = q->a_nib >> PAGE_SHIFT;
>> + ret = vfio_pin_pages(mdev_dev(q->matrix_mdev->mdev), &q->a_pfn, 1,
>> + IOMMU_READ | IOMMU_WRITE, &h_pfn);
>> + switch (ret) {
>> + case 1:
>> + break;
>> + case -EINVAL:
>> + case -E2BIG:
>> + status.response_code = AP_RESPONSE_INVALID_ADDRESS;
>> + /* Fallthrough */
>> + default:
>> + return status;
>
> Can we actually hit the default label? AFICT you would return an
> all-zero status, i.e. status.response_code == 0 'Normal completion'.

hum right, the setting of AP_INVALID_ADDRESS should be in the default
and there is no need for the two error cases, they will match the default.

>
>> + }
>> +
>> + kvm = q->matrix_mdev->kvm;
>> + gisa = kvm->arch.gisa_int.origin;
>> +
>> + h_nib = (h_pfn << PAGE_SHIFT) | (q->a_nib & ~PAGE_MASK);
>> + aqic_gisa.gisc = q->a_isc;
>> + aqic_gisa.isc = kvm_s390_gisc_register(kvm, q->a_isc);
>> + aqic_gisa.ir = 1;
>> + aqic_gisa.gisa = gisa->next_alert >> 4;
>
> Why gisa->next_alert? Isn't this supposed to get set to gisa origin
> (without some bits on the left)?

Someone already asked this question.
The answer is: look at the ap_qirq_ctrl structure, you will see that the
gisa field is 27 bits wide.

>
>> +
>> + status = ap_aqic(q->apqn, aqic_gisa, (void *)h_nib);
>> + switch (status.response_code) {
>> + case AP_RESPONSE_NORMAL:
>> + /* See if we did clear older IRQ configuration */
>> + if (q->p_pfn)
>> + vfio_unpin_pages(mdev_dev(q->matrix_mdev->mdev),
>> + &q->p_pfn, 1);
>> + if (q->p_isc != VFIO_AP_ISC_INVALID)
>> + kvm_s390_gisc_unregister(kvm, q->p_isc);
>> + q->p_pfn = q->a_pfn;
>> + q->p_isc = q->a_isc;
>> + break;
>> + case AP_RESPONSE_OTHERWISE_CHANGED:
>> + /* We could not modify IRQ setings: clear new configuration */
>> + vfio_unpin_pages(mdev_dev(q->matrix_mdev->mdev), &q->a_pfn, 1);
>> + kvm_s390_gisc_unregister(kvm, q->a_isc);
>
> Hm, see below. Wouldn't you want to set a_isc to VFIO_AP_ISC_INVALID?

grrr!!! when did I insert these 3 lines, it was OK in previous series!
all 3 lines, vfio_unpin() / gisc_unregister / break must go away.

>
>> + break;
>> + default: /* Fall Through */
>
> Is it 'break' or is it 'Fall Through'?

it is a fall through

>
>> + pr_warn("%s: apqn %04x: response: %02x\n", __func__, q->apqn,
>> + status.response_code);
>> + vfio_ap_free_irq_data(q);
>> + break;
>> + }
>> +
>> + return status;
>> +}

--
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany