Re: [PATCH v10 03/16] s390/vfio-ap: manage link between queue struct and matrix mdev

[Halil Pasic <pasic@linux.ibm.com>]

On Fri, 21 Aug 2020 15:56:03 -0400
Tony Krowiak <akrowiak@linux.ibm.com> wrote:

> Let's create links between each queue device bound to the vfio_ap device

How about: Let us establish a bidirectional link...

we kind of had a shaky queue --> matrix_mdev link prior to this patch,
you are making this one solid and you are adding the matrix_mdev -->
queue link.

> driver and the matrix mdev to which the queue is assigned. The idea is to
> facilitate efficient retrieval of the objects representing the queue
> devices and matrix mdevs as well as to verify that a queue assigned to
> a matrix mdev is bound to the driver.
> 

I will have to look at the rest of the series to figure the usage out.
One thought in the back of my head is that if vfio_ap_get_queue(apqn) is
already O(1) the there is not much efficiency to gain by adding another
hashtable whose keys are apqns and values queues.

But I don't want to hang up myself on this.

> The links will be created as follows:
> 
>    * When the queue device is probed, if its APQN is assigned to a matrix
>      mdev, the structures representing the queue device and the matrix mdev
>      will be linked.
> 
>    * When an adapter or domain is assigned to a matrix mdev, for each new
>      APQN assigned that references a queue device bound to the vfio_ap
>      device driver, the structures representing the queue device and the
>      matrix mdev will be linked.
> 
> The links will be removed as follows:
> 
>    * When the queue device is removed, if its APQN is assigned to a matrix
>      mdev, the structures representing the queue device and the matrix mdev
>      will be unlinked.
> 
>    * When an adapter or domain is unassigned from a matrix mdev, for each
>      APQN unassigned that references a queue device bound to the vfio_ap
>      device driver, the structures representing the queue device and the
>      matrix mdev will be unlinked.
> 
> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>

Except for the things pointed out by Connie and Christian, LGTM.

> ---
>  drivers/s390/crypto/vfio_ap_ops.c     | 132 +++++++++++++++++++++++++-
>  drivers/s390/crypto/vfio_ap_private.h |   2 +
>  2 files changed, 129 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
> index ad3925f04f61..2e37ee82e422 100644
> --- a/drivers/s390/crypto/vfio_ap_ops.c
> +++ b/drivers/s390/crypto/vfio_ap_ops.c
> @@ -50,6 +50,19 @@ static struct vfio_ap_queue *vfio_ap_get_queue(unsigned long apqn)
>  	return q;
>  }
>  
> +static struct vfio_ap_queue *vfio_ap_get_mdev_queue(struct ap_matrix_mdev *matrix_mdev,
> +						    unsigned long apqn)
> +{
> +	struct vfio_ap_queue *q;
> +
> +	hash_for_each_possible(matrix_mdev->qtable, q, mdev_qnode, apqn) {
> +		if (q && (q->apqn == apqn))
> +			return q;
> +	}
> +
> +	return NULL;
> +}
> +
>  /**
>   * vfio_ap_wait_for_irqclear
>   * @apqn: The AP Queue number
> @@ -160,7 +173,6 @@ static struct ap_queue_status vfio_ap_irq_disable(struct vfio_ap_queue *q)
>  		  status.response_code);
>  end_free:
>  	vfio_ap_free_aqic_resources(q);
> -	q->matrix_mdev = NULL;
>  	return status;
>  }
>  
> @@ -262,7 +274,6 @@ static int handle_pqap(struct kvm_vcpu *vcpu)
>  	struct vfio_ap_queue *q;
>  	struct ap_queue_status qstatus = {
>  			       .response_code = AP_RESPONSE_Q_NOT_AVAIL, };
> -	struct ap_matrix_mdev *matrix_mdev;
>  
>  	/* If we do not use the AIV facility just go to userland */
>  	if (!(vcpu->arch.sie_block->eca & ECA_AIV))
> @@ -273,14 +284,11 @@ static int handle_pqap(struct kvm_vcpu *vcpu)
>  
>  	if (!vcpu->kvm->arch.crypto.pqap_hook)
>  		goto out_unlock;
> -	matrix_mdev = container_of(vcpu->kvm->arch.crypto.pqap_hook,
> -				   struct ap_matrix_mdev, pqap_hook);
>  
>  	q = vfio_ap_get_queue(apqn);
>  	if (!q)
>  		goto out_unlock;
>  
> -	q->matrix_mdev = matrix_mdev;
>  	status = vcpu->run->s.regs.gprs[1];
>  
>  	/* If IR bit(16) is set we enable the interrupt */
> @@ -320,6 +328,7 @@ static int vfio_ap_mdev_create(struct kobject *kobj, struct mdev_device *mdev)
>  
>  	matrix_mdev->mdev = mdev;
>  	vfio_ap_matrix_init(&matrix_dev->info, &matrix_mdev->matrix);
> +	hash_init(matrix_mdev->qtable);
>  	mdev_set_drvdata(mdev, matrix_mdev);
>  	matrix_mdev->pqap_hook.hook = handle_pqap;
>  	matrix_mdev->pqap_hook.owner = THIS_MODULE;
> @@ -548,6 +557,87 @@ static int vfio_ap_mdev_verify_no_sharing(struct ap_matrix_mdev *matrix_mdev)
>  	return 0;
>  }
>  
> +enum qlink_type {
> +	LINK_APID,
> +	LINK_APQI,
> +	UNLINK_APID,
> +	UNLINK_APQI,
> +};
> +
> +static void vfio_ap_mdev_link_queue(struct ap_matrix_mdev *matrix_mdev,
> +				    unsigned long apid, unsigned long apqi)
> +{
> +	struct vfio_ap_queue *q;
> +
> +	q = vfio_ap_get_queue(AP_MKQID(apid, apqi));
> +	if (q) {
> +		q->matrix_mdev = matrix_mdev;
> +		hash_add(matrix_mdev->qtable,
> +			 &q->mdev_qnode, q->apqn);
> +	}
> +}
> +
> +static void vfio_ap_mdev_unlink_queue(unsigned long apid, unsigned long apqi)
> +{
> +	struct vfio_ap_queue *q;
> +
> +	q = vfio_ap_get_queue(AP_MKQID(apid, apqi));
> +	if (q) {
> +		q->matrix_mdev = NULL;
> +		hash_del(&q->mdev_qnode);
> +	}
> +}
> +
> +/**
> + * vfio_ap_mdev_link_queues
> + *
> + * @matrix_mdev: The matrix mdev to link.
> + * @type:	 The type of @qlink_id.
> + * @qlink_id:	 The APID or APQI of the queues to link.
> + *
> + * Sets or clears the links between the queues with the specified @qlink_id
> + * and the @matrix_mdev:
> + *     @type == LINK_APID: Set the links between the @matrix_mdev and the
> + *                         queues with the specified @qlink_id (APID)
> + *     @type == LINK_APQI: Set the links between the @matrix_mdev and the
> + *                         queues with the specified @qlink_id (APQI)
> + *     @type == UNLINK_APID: Clear the links between the @matrix_mdev and the
> + *                           queues with the specified @qlink_id (APID)
> + *     @type == UNLINK_APQI: Clear the links between the @matrix_mdev and the
> + *                           queues with the specified @qlink_id (APQI)
> + */
> +static void vfio_ap_mdev_link_queues(struct ap_matrix_mdev *matrix_mdev,
> +				     enum qlink_type type,
> +				     unsigned long qlink_id)
> +{
> +	unsigned long id;
> +
> +	switch (type) {
> +	case LINK_APID:
> +		for_each_set_bit_inv(id, matrix_mdev->matrix.aqm,
> +				     matrix_mdev->matrix.aqm_max + 1)
> +			vfio_ap_mdev_link_queue(matrix_mdev, qlink_id, id);
> +		break;
> +	case UNLINK_APID:
> +		for_each_set_bit_inv(id, matrix_mdev->matrix.aqm,
> +				     matrix_mdev->matrix.aqm_max + 1)
> +			vfio_ap_mdev_unlink_queue(qlink_id, id);
> +		break;
> +	case LINK_APQI:
> +		for_each_set_bit_inv(id, matrix_mdev->matrix.apm,
> +				     matrix_mdev->matrix.apm_max + 1)
> +			vfio_ap_mdev_link_queue(matrix_mdev, id, qlink_id);
> +		break;
> +	case UNLINK_APQI:
> +		for_each_set_bit_inv(id, matrix_mdev->matrix.apm,
> +				     matrix_mdev->matrix.apm_max + 1)
> +			vfio_ap_mdev_link_queue(matrix_mdev, id, qlink_id);
> +		break;
> +	default:
> +		WARN_ON_ONCE(1);
> +	}
> +}
> +
>  /**
>   * assign_adapter_store
>   *
> @@ -617,6 +707,7 @@ static ssize_t assign_adapter_store(struct device *dev,
>  	if (ret)
>  		goto share_err;
>  
> +	vfio_ap_mdev_link_queues(matrix_mdev, LINK_APID, apid);
>  	ret = count;
>  	goto done;
>  
> @@ -668,6 +759,7 @@ static ssize_t unassign_adapter_store(struct device *dev,
>  
>  	mutex_lock(&matrix_dev->lock);
>  	clear_bit_inv((unsigned long)apid, matrix_mdev->matrix.apm);
> +	vfio_ap_mdev_link_queues(matrix_mdev, UNLINK_APID, apid);
>  	mutex_unlock(&matrix_dev->lock);
>  
>  	return count;
> @@ -758,6 +850,7 @@ static ssize_t assign_domain_store(struct device *dev,
>  	if (ret)
>  		goto share_err;
>  
> +	vfio_ap_mdev_link_queues(matrix_mdev, LINK_APQI, apqi);
>  	ret = count;
>  	goto done;
>  
> @@ -810,6 +903,7 @@ static ssize_t unassign_domain_store(struct device *dev,
>  
>  	mutex_lock(&matrix_dev->lock);
>  	clear_bit_inv((unsigned long)apqi, matrix_mdev->matrix.aqm);
> +	vfio_ap_mdev_link_queues(matrix_mdev, UNLINK_APQI, apqi);
>  	mutex_unlock(&matrix_dev->lock);
>  
>  	return count;
> @@ -1282,6 +1376,29 @@ void vfio_ap_mdev_unregister(void)
>  	mdev_unregister_device(&matrix_dev->device);
>  }
>  
> +/**
> + * vfio_ap_queue_link_mdev
> + *
> + * @q: The queue to link with the matrix mdev.
> + *
> + * Links @q with the matrix mdev to which the queue's APQN is assigned.
> + */
> +static void vfio_ap_queue_link_mdev(struct vfio_ap_queue *q)
> +{
> +	unsigned long apid = AP_QID_CARD(q->apqn);
> +	unsigned long apqi = AP_QID_QUEUE(q->apqn);
> +	struct ap_matrix_mdev *matrix_mdev;
> +
> +	list_for_each_entry(matrix_mdev, &matrix_dev->mdev_list, node) {
> +		if (test_bit_inv(apid, matrix_mdev->matrix.apm) &&
> +		    test_bit_inv(apqi, matrix_mdev->matrix.aqm)) {
> +			q->matrix_mdev = matrix_mdev;
> +			hash_add(matrix_mdev->qtable, &q->mdev_qnode, q->apqn);
> +			break;
> +		}
> +	}
> +}
> +
>  int vfio_ap_mdev_probe_queue(struct ap_queue *queue)
>  {
>  	struct vfio_ap_queue *q;
> @@ -1290,9 +1407,12 @@ int vfio_ap_mdev_probe_queue(struct ap_queue *queue)
>  	if (!q)
>  		return -ENOMEM;
>  
> +	mutex_lock(&matrix_dev->lock);
>  	dev_set_drvdata(&queue->ap_dev.device, q);
>  	q->apqn = queue->qid;
>  	q->saved_isc = VFIO_AP_ISC_INVALID;
> +	vfio_ap_queue_link_mdev(q);
> +	mutex_unlock(&matrix_dev->lock);
>  
>  	return 0;
>  }
> @@ -1309,6 +1429,8 @@ void vfio_ap_mdev_remove_queue(struct ap_queue *queue)
>  	apqi = AP_QID_QUEUE(q->apqn);
>  	vfio_ap_mdev_reset_queue(apid, apqi, 1);
>  	vfio_ap_irq_disable(q);
> +	if (q->matrix_mdev)
> +		hash_del(&q->mdev_qnode);
>  	kfree(q);
>  	mutex_unlock(&matrix_dev->lock);
>  }
> diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
> index a2aa05bec718..57da703b549a 100644
> --- a/drivers/s390/crypto/vfio_ap_private.h
> +++ b/drivers/s390/crypto/vfio_ap_private.h
> @@ -87,6 +87,7 @@ struct ap_matrix_mdev {
>  	struct kvm *kvm;
>  	struct kvm_s390_module_hook pqap_hook;
>  	struct mdev_device *mdev;
> +	DECLARE_HASHTABLE(qtable, 8);
>  };
>  
>  extern int vfio_ap_mdev_register(void);
> @@ -98,6 +99,7 @@ struct vfio_ap_queue {
>  	int	apqn;
>  #define VFIO_AP_ISC_INVALID 0xff
>  	unsigned char saved_isc;
> +	struct hlist_node mdev_qnode;
>  };
>  
>  int vfio_ap_mdev_probe_queue(struct ap_queue *queue);