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

[Pierre Morel]

On 29/04/2019 18:50, Halil Pasic wrote:
> On Fri, 26 Apr 2019 15:01:27 +0200
> Pierre Morel <pmorel@xxxxxxxxxxxxx> 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 BÃblingen - Germany