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

Jason J. Herne
2022-03-15T14:14:06Z

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)