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

Halil Pasic
2019-04-29T16:50:13Z

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'.

> + }
> +
> + 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)?

> +
> + 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?

> + break;
> + default: /* Fall Through */

Is it 'break' or is it '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;
> +}