Re: [PATCH v18 12/18] s390/vfio-ap: reset queues after adapter/domain unassignment

["Jason J. Herne" <jjherne@linux.ibm.com>]

On 2/14/22 19:50, Tony Krowiak wrote:
> When an adapter or domain is unassigned from an mdev providing the AP
> configuration to a running KVM guest, one or more of the guest's queues may
> get dynamically removed. Since the removed queues could get re-assigned to
> another mdev, they need to be reset. So, when an adapter or domain is
> unassigned from the mdev, the queues that are removed from the guest's
> AP configuration will be reset.
> 
> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
> ---
...
>   
> +static void vfio_ap_unlink_apqn_fr_mdev(struct ap_matrix_mdev *matrix_mdev,
> +					unsigned long apid, unsigned long apqi,
> +					struct ap_queue_table *qtable)
> +{
> +	struct vfio_ap_queue *q;
> +
> +	q = vfio_ap_mdev_get_queue(matrix_mdev, AP_MKQID(apid, apqi));
> +	/* If the queue is assigned to the matrix mdev, unlink it. */
> +	if (q)
> +		vfio_ap_unlink_queue_fr_mdev(q);
> +
> +	/* If the queue is assigned to the APCB, store it in @qtable. */
> +	if (test_bit_inv(apid, matrix_mdev->shadow_apcb.apm) &&
> +	    test_bit_inv(apqi, matrix_mdev->shadow_apcb.aqm))
> +		hash_add(qtable->queues, &q->mdev_qnode, q->apqn);
> +}
> +
> +/**
> + * vfio_ap_mdev_unlink_adapter - unlink all queues associated with unassigned
> + *				 adapter from the matrix mdev to which the
> + *				 adapter was assigned.
> + * @matrix_mdev: the matrix mediated device to which the adapter was assigned.
> + * @apid: the APID of the unassigned adapter.
> + * @qtable: table for storing queues associated with unassigned adapter.
> + */
>   static void vfio_ap_mdev_unlink_adapter(struct ap_matrix_mdev *matrix_mdev,
> -					unsigned long apid)
> +					unsigned long apid,
> +					struct ap_queue_table *qtable)
>   {
>   	unsigned long apqi;
> +
> +	for_each_set_bit_inv(apqi, matrix_mdev->matrix.aqm, AP_DOMAINS)
> +		vfio_ap_unlink_apqn_fr_mdev(matrix_mdev, apid, apqi, qtable);
> +}

Here is an alternate version of the above two functions that stops the
profileration of the qtables variable into vfio_ap_unlink_apqn_fr_mdev.
It may seem like a change with no benefit, but it simplifies things a
bit and avoids the reader from having to sink three functions deep to
find out where qtables is used. This is 100% untested.


static bool vfio_ap_unlink_apqn_fr_mdev(struct ap_matrix_mdev *matrix_mdev,
					unsigned long apid, unsigned long apqi)
{
	struct vfio_ap_queue *q;

	q = vfio_ap_mdev_get_queue(matrix_mdev, AP_MKQID(apid, apqi));
	/* If the queue is assigned to the matrix mdev, unlink it. */
	if (q) {
		vfio_ap_unlink_queue_fr_mdev(q);
		return true;
	}
	return false;
}

static void vfio_ap_mdev_unlink_adapter(struct ap_matrix_mdev *matrix_mdev,
					unsigned long apid,
					struct ap_queue_table *qtable)
{
	unsigned long apqi;
	bool unlinked;

	for_each_set_bit_inv(apqi, matrix_mdev->matrix.aqm, AP_DOMAINS) {
		unlinked = vfio_ap_unlink_apqn_fr_mdev(matrix_mdev, apid, apqi, qtable);

		if (unlinked && qtable) {
			if (test_bit_inv(apid, matrix_mdev->shadow_apcb.apm) &&
			    test_bit_inv(apqi, matrix_mdev->shadow_apcb.aqm))
				hash_add(qtable->queues, &q->mdev_qnode,
					 q->apqn);
		}
	}
}


> +static void vfio_ap_mdev_hot_unplug_adapter(struct ap_matrix_mdev *matrix_mdev,
> +					    unsigned long apid)
> +{
> +	int bkt;
>   	struct vfio_ap_queue *q;
> +	struct ap_queue_table qtable;
> +	hash_init(qtable.queues);
> +	vfio_ap_mdev_unlink_adapter(matrix_mdev, apid, &qtable);
> +
> +	if (test_bit_inv(apid, matrix_mdev->shadow_apcb.apm)) {
> +		clear_bit_inv(apid, matrix_mdev->shadow_apcb.apm);
> +		vfio_ap_mdev_hotplug_apcb(matrix_mdev);
> +	}
>   
> -	for_each_set_bit_inv(apqi, matrix_mdev->matrix.aqm, AP_DOMAINS) {
> -		q = vfio_ap_mdev_get_queue(matrix_mdev, AP_MKQID(apid, apqi));
> +	vfio_ap_mdev_reset_queues(&qtable);
>   
> -		if (q)
> -			vfio_ap_mdev_unlink_queue(q);
> +	hash_for_each(qtable.queues, bkt, q, mdev_qnode) {

This comment applies to all instances of btk: What is btk? Can we come
up with a more descriptive name?

> +		vfio_ap_unlink_mdev_fr_queue(q);
> +		hash_del(&q->mdev_qnode);
>   	}
>   }
...
> @@ -1273,9 +1320,9 @@ static void vfio_ap_mdev_unset_kvm(struct ap_matrix_mdev *matrix_mdev,
>   		mutex_lock(&kvm->lock);
>   		mutex_lock(&matrix_dev->mdevs_lock);
>   
> -		kvm_arch_crypto_clear_masks(kvm);
> -		vfio_ap_mdev_reset_queues(matrix_mdev);
> -		kvm_put_kvm(kvm);
> +		kvm_arch_crypto_clear_masks(matrix_mdev->kvm);
> +		vfio_ap_mdev_reset_queues(&matrix_mdev->qtable);
> +		kvm_put_kvm(matrix_mdev->kvm);
>   		matrix_mdev->kvm = NULL;

I understand changing the call to vfio_ap_mdev_reset_queues, but why are we changing the
kvm pointer on the surrounding lines?

>   
>   		mutex_unlock(&matrix_dev->mdevs_lock);
> @@ -1328,14 +1375,17 @@ static int vfio_ap_mdev_reset_queue(struct vfio_ap_queue *q, unsigned int retry)
>   
>   	if (!q)
>   		return 0;
> +	q->reset_rc = 0;

This line seems unnecessary. You set q->reset_rc in every single case below, so this 0
will always get overwritten.

>   retry_zapq:
>   	status = ap_zapq(q->apqn);
>   	switch (status.response_code) {
>   	case AP_RESPONSE_NORMAL:
>   		ret = 0;
> +		q->reset_rc = status.response_code;
>   		break;
>   	case AP_RESPONSE_RESET_IN_PROGRESS:
> +		q->reset_rc = status.response_code;
>   		if (retry--) {
>   			msleep(20);
>   			goto retry_zapq;
> @@ -1345,13 +1395,20 @@ static int vfio_ap_mdev_reset_queue(struct vfio_ap_queue *q, unsigned int retry)
>   	case AP_RESPONSE_Q_NOT_AVAIL:
>   	case AP_RESPONSE_DECONFIGURED:
>   	case AP_RESPONSE_CHECKSTOPPED:
> -		WARN_ON_ONCE(status.irq_enabled);
> +		WARN_ONCE(status.irq_enabled,
> +			  "PQAP/ZAPQ for %02x.%04x failed with rc=%u while IRQ enabled",
> +			  AP_QID_CARD(q->apqn), AP_QID_QUEUE(q->apqn),
> +			  status.response_code);
> +		q->reset_rc = status.response_code;
>   		ret = -EBUSY;
>   		goto free_resources;
>   	default:
>   		/* things are really broken, give up */
> -		WARN(true, "PQAP/ZAPQ completed with invalid rc (%x)\n",
> +		WARN(true,
> +		     "PQAP/ZAPQ for %02x.%04x failed with invalid rc=%u\n",
> +		     AP_QID_CARD(q->apqn), AP_QID_QUEUE(q->apqn),
>   		     status.response_code);
> +		q->reset_rc = status.response_code;
>   		return -EIO;
>   	}
...

-- 
-- Jason J. Herne (jjherne@linux.ibm.com)