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Date:   Thu, 26 Nov 2020 15:45:38 +0100
From:   Halil Pasic <pasic@...ux.ibm.com>
To:     Tony Krowiak <akrowiak@...ux.ibm.com>
Cc:     linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, freude@...ux.ibm.com, borntraeger@...ibm.com,
        cohuck@...hat.com, mjrosato@...ux.ibm.com,
        alex.williamson@...hat.com, kwankhede@...dia.com,
        fiuczy@...ux.ibm.com, frankja@...ux.ibm.com, david@...hat.com,
        hca@...ux.ibm.com, gor@...ux.ibm.com
Subject: Re: [PATCH v12 05/17] s390/vfio-ap: manage link between queue
 struct and matrix mdev

On Tue, 24 Nov 2020 16:40:04 -0500
Tony Krowiak <akrowiak@...ux.ibm.com> wrote:

> Let's create links between each queue device bound to the vfio_ap device
> 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.
> 
> 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@...ux.ibm.com>

Actually some aspects of this look much better than last time,
but I'm afraid there one new issue that must be corrected -- see below.

> ---
>  drivers/s390/crypto/vfio_ap_ops.c     | 161 +++++++++++++++++++++++---
>  drivers/s390/crypto/vfio_ap_private.h |   3 +
>  2 files changed, 146 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
> index dc699fd54505..07caf871943c 100644
> --- a/drivers/s390/crypto/vfio_ap_ops.c
> +++ b/drivers/s390/crypto/vfio_ap_ops.c
> @@ -28,7 +28,6 @@ static int vfio_ap_mdev_reset_queues(struct mdev_device *mdev);
>  
>  /**
>   * vfio_ap_get_queue: Retrieve a queue with a specific APQN.
> - * @matrix_mdev: the associated mediated matrix
>   * @apqn: The queue APQN
>   *
>   * Retrieve a queue with a specific APQN from the AP queue devices attached to
> @@ -36,32 +35,36 @@ static int vfio_ap_mdev_reset_queues(struct mdev_device *mdev);
>   *
>   * Returns the pointer to the vfio_ap_queue with the specified APQN, or NULL.
>   */
> -static struct vfio_ap_queue *vfio_ap_get_queue(
> -					struct ap_matrix_mdev *matrix_mdev,
> -					int apqn)
> +static struct vfio_ap_queue *vfio_ap_get_queue(int apqn)
>  {
>  	struct ap_queue *queue;
>  	struct vfio_ap_queue *q = NULL;
>  
> -	if (!test_bit_inv(AP_QID_CARD(apqn), matrix_mdev->matrix.apm))
> -		return NULL;
> -	if (!test_bit_inv(AP_QID_QUEUE(apqn), matrix_mdev->matrix.aqm))
> -		return NULL;
> -
>  	queue = ap_get_qdev(apqn);
>  	if (!queue)
>  		return NULL;
>  
>  	put_device(&queue->ap_dev.device);
>  
> -	if (queue->ap_dev.device.driver == &matrix_dev->vfio_ap_drv->driver) {
> +	if (queue->ap_dev.device.driver == &matrix_dev->vfio_ap_drv->driver)
>  		q = dev_get_drvdata(&queue->ap_dev.device);
> -		q->matrix_mdev = matrix_mdev;
> -	}
>  
>  	return q;
>  }
>  
> +static struct vfio_ap_queue *
> +vfio_ap_mdev_get_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
> @@ -172,7 +175,6 @@ 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;
>  }
>  
> @@ -288,7 +290,7 @@ static int handle_pqap(struct kvm_vcpu *vcpu)
>  	matrix_mdev = container_of(vcpu->kvm->arch.crypto.pqap_hook,
>  				   struct ap_matrix_mdev, pqap_hook);
>  
> -	q = vfio_ap_get_queue(matrix_mdev, apqn);
> +	q = vfio_ap_mdev_get_queue(matrix_mdev, apqn);
>  	if (!q)
>  		goto out_unlock;
>  
> @@ -331,6 +333,7 @@ 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;
> @@ -559,6 +562,87 @@ static int vfio_ap_mdev_verify_no_sharing(struct ap_matrix_mdev *matrix_mdev)
>  	return 0;
>  }
>  
> +enum qlink_action {
> +	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);
> +	}
> +}



I would do 

+static void vfio_ap_mdev_unlink_queue(struct vfio_ap_queue *q)
+{
+	if (!q)
+		return;
+	q->matrix_mdev = NULL;
+	hash_del(&q->mdev_qnode);
+}
+
+static void vfio_ap_mdev_unlink_queue_by_id(unsigned long apid, unsigned long apqi)
+{
+	struct vfio_ap_queue *q = vfio_ap_get_queue(AP_MKQID(apid, apqi));
+	
+	vfio_ap_mdev_unlink_queue(q);
+}

> +
> +/**
> + * vfio_ap_mdev_manage_qlinks
> + *
> + * @matrix_mdev: The matrix mdev to link.
> + * @action:	 The action to take on @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:
> + *	@action == LINK_APID:	Set the links between the @matrix_mdev and the
> + *				queues with the specified @qlink_id (APID)
> + *	@action == LINK_APQI:	Set the links between the @matrix_mdev and the
> + *				queues with the specified @qlink_id (APQI)
> + *	@action == UNLINK_APID:	Clear the links between the @matrix_mdev and the
> + *				queues with the specified @qlink_id (APID)
> + *	@action == UNLINK_APQI:	Clear the links between the @matrix_mdev and the
> + *				queues with the specified @qlink_id (APQI)
> + */
> +static void vfio_ap_mdev_manage_qlinks(struct ap_matrix_mdev *matrix_mdev,
> +				       enum qlink_action action,
> +				       unsigned long qlink_id)
> +{
> +	unsigned long id;
> +
> +	switch (action) {
> +	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
>   *
> @@ -628,6 +712,7 @@ static ssize_t assign_adapter_store(struct device *dev,
>  	if (ret)
>  		goto share_err;
>  
> +	vfio_ap_mdev_manage_qlinks(matrix_mdev, LINK_APID, apid);
>  	ret = count;
>  	goto done;
>  
> @@ -679,6 +764,7 @@ 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_manage_qlinks(matrix_mdev, UNLINK_APID, apid);
>  	mutex_unlock(&matrix_dev->lock);
>  
>  	return count;
> @@ -769,6 +855,7 @@ static ssize_t assign_domain_store(struct device *dev,
>  	if (ret)
>  		goto share_err;
>  
> +	vfio_ap_mdev_manage_qlinks(matrix_mdev, LINK_APQI, apqi);
>  	ret = count;
>  	goto done;
>  
> @@ -821,6 +908,7 @@ 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_manage_qlinks(matrix_mdev, UNLINK_APQI, apqi);
>  	mutex_unlock(&matrix_dev->lock);
>  
>  	return count;
> @@ -1155,6 +1243,11 @@ static int vfio_ap_mdev_reset_queues(struct mdev_device *mdev)
>  			     matrix_mdev->matrix.apm_max + 1) {
>  		for_each_set_bit_inv(apqi, matrix_mdev->matrix.aqm,
>  				     matrix_mdev->matrix.aqm_max + 1) {
> +			q = vfio_ap_mdev_get_queue(matrix_mdev,
> +						   AP_MKQID(apid, apqi));
> +			if (!q)
> +				continue;
> +
>  			ret = vfio_ap_mdev_reset_queue(apid, apqi, 1);
>  			/*
>  			 * Regardless whether a queue turns out to be busy, or
> @@ -1164,9 +1257,7 @@ static int vfio_ap_mdev_reset_queues(struct mdev_device *mdev)
>  			if (ret)
>  				rc = ret;
>  
> -			q = vfio_ap_get_queue(matrix_mdev, AP_MKQID(apid, apqi);
> -			if (q)
> -				vfio_ap_free_aqic_resources(q);
> +			vfio_ap_free_aqic_resources(q);
>  		}
>  	}
>  
> @@ -1292,6 +1383,29 @@ 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;
> +		}
> +	}
> +}
> +
>  /**
>   * vfio_ap_mdev_probe_queue:
>   *
> @@ -1305,9 +1419,13 @@ int vfio_ap_mdev_probe_queue(struct ap_device *apdev)
>  	q = kzalloc(sizeof(*q), GFP_KERNEL);
>  	if (!q)
>  		return -ENOMEM;
> +	mutex_lock(&matrix_dev->lock);
>  	dev_set_drvdata(&apdev->device, q);
>  	q->apqn = to_ap_queue(&apdev->device)->qid;
>  	q->saved_isc = VFIO_AP_ISC_INVALID;
> +	vfio_ap_queue_link_mdev(q);
> +	mutex_unlock(&matrix_dev->lock);
> +
>  	return 0;
>  }
>  
> @@ -1328,7 +1446,14 @@ void vfio_ap_mdev_remove_queue(struct ap_device *apdev)
>  	apid = AP_QID_CARD(q->apqn);
>  	apqi = AP_QID_QUEUE(q->apqn);
>  	vfio_ap_mdev_reset_queue(apid, apqi, 1);

Does it make sense to reset if !q->matrix_dev?

> -	vfio_ap_irq_disable(q);
> +	if (q->matrix_mdev) {
> +		if (q->matrix_mdev->kvm) {
> +			vfio_ap_free_aqic_resources(q);

Again this belongs to the previous patch.

> +			kvm_put_kvm(q->matrix_mdev->kvm);

This kvm_put_kvm() makes no sense to me! Please explain. Where
is the corresponding kvm_get_kvm()?

> +		}
> +		hash_del(&q->mdev_qnode);
> +		q->matrix_mdev = NULL;

This shouuld be an unlink_queue(q).

> +	}
>  	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 d9003de4fbad..4e5cc72fc0db 100644
> --- a/drivers/s390/crypto/vfio_ap_private.h
> +++ b/drivers/s390/crypto/vfio_ap_private.h
> @@ -18,6 +18,7 @@
>  #include <linux/delay.h>
>  #include <linux/mutex.h>
>  #include <linux/kvm_host.h>
> +#include <linux/hashtable.h>
>  
>  #include "ap_bus.h"
>  
> @@ -86,6 +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);
> @@ -97,6 +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_device *queue);

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