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Date:   Mon, 11 Jan 2021 20:17:52 +0100
From:   Halil Pasic <pasic@linux.ibm.com>
To:     Tony Krowiak <akrowiak@linux.ibm.com>
Cc:     linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org, freude@linux.ibm.com, borntraeger@de.ibm.com,
        cohuck@redhat.com, mjrosato@linux.ibm.com,
        alex.williamson@redhat.com, kwankhede@nvidia.com,
        fiuczy@linux.ibm.com, frankja@linux.ibm.com, david@redhat.com,
        hca@linux.ibm.com, gor@linux.ibm.com
Subject: Re: [PATCH v13 05/15] s390/vfio-ap: manage link between queue
 struct and matrix mdev
Message-ID: <20210111201752.21a41db4.pasic@linux.ibm.com>
In-Reply-To: <20201223011606.5265-6-akrowiak@linux.ibm.com>
References: <20201223011606.5265-1-akrowiak@linux.ibm.com>
        <20201223011606.5265-6-akrowiak@linux.ibm.com>
Organization: IBM
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On Tue, 22 Dec 2020 20:15:56 -0500
Tony Krowiak <akrowiak@linux.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's APQN 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@linux.ibm.com>

Reviewed-by: Halil Pasic <pasic@linux.ibm.com>

> ---
>  drivers/s390/crypto/vfio_ap_ops.c     | 140 +++++++++++++++++++++-----
>  drivers/s390/crypto/vfio_ap_private.h |   3 +
>  2 files changed, 117 insertions(+), 26 deletions(-)
> 
> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
> index 835c963ae16d..cdcc6378b4a5 100644
> --- a/drivers/s390/crypto/vfio_ap_ops.c
> +++ b/drivers/s390/crypto/vfio_ap_ops.c
> @@ -27,33 +27,17 @@
>  static int vfio_ap_mdev_reset_queues(struct mdev_device *mdev);
>  static struct vfio_ap_queue *vfio_ap_find_queue(int apqn);
>  
> -/**
> - * vfio_ap_get_queue: Retrieve a queue with a specific APQN from a list
> - * @matrix_mdev: the associated mediated matrix
> - * @apqn: The queue APQN
> - *
> - * Retrieve a queue with a specific APQN from the list of the
> - * devices of the vfio_ap_drv.
> - * Verify that the APID and the APQI are set in the matrix.
> - *
> - * Returns the pointer to the associated vfio_ap_queue
> - */
> -static struct vfio_ap_queue *vfio_ap_get_queue(
> -					struct ap_matrix_mdev *matrix_mdev,
> -					int apqn)
> +static struct vfio_ap_queue *
> +vfio_ap_mdev_get_queue(struct ap_matrix_mdev *matrix_mdev, unsigned long apqn)
>  {
> -	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;
> +	struct vfio_ap_queue *q;
>  
> -	q = vfio_ap_find_queue(apqn);
> -	if (q)
> -		q->matrix_mdev = matrix_mdev;
> +	hash_for_each_possible(matrix_mdev->qtable, q, mdev_qnode, apqn) {
> +		if (q && (q->apqn == apqn))
> +			return q;
> +	}
>  
> -	return q;
> +	return NULL;
>  }
>  
>  /**
> @@ -166,7 +150,6 @@ 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;
>  }
>  
> @@ -282,7 +265,7 @@ 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;
>  
> @@ -325,6 +308,7 @@ 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;
> @@ -553,6 +537,50 @@ static int vfio_ap_mdev_verify_no_sharing(struct ap_matrix_mdev *matrix_mdev)
>  	return 0;
>  }
>  
> +static void vfio_ap_mdev_link_queue(struct ap_matrix_mdev *matrix_mdev,
> +				    struct vfio_ap_queue *q)
> +{
> +	if (q) {
> +		q->matrix_mdev = matrix_mdev;
> +		hash_add(matrix_mdev->qtable,
> +			 &q->mdev_qnode, q->apqn);
> +	}
> +}
> +
> +static void vfio_ap_mdev_link_apqn(struct ap_matrix_mdev *matrix_mdev, int apqn)
> +{
> +	struct vfio_ap_queue *q;
> +
> +	q = vfio_ap_find_queue(apqn);
> +	vfio_ap_mdev_link_queue(matrix_mdev, q);
> +}
> +
> +static void vfio_ap_mdev_unlink_queue(struct vfio_ap_queue *q)
> +{
> +	if (q) {
> +		q->matrix_mdev = NULL;
> +		hash_del(&q->mdev_qnode);
> +	}
> +}
> +
> +static void vfio_ap_mdev_unlink_apqn(int apqn)
> +{
> +	struct vfio_ap_queue *q;
> +
> +	q = vfio_ap_find_queue(apqn);
> +	vfio_ap_mdev_unlink_queue(q);
> +}
> +
> +static void vfio_ap_mdev_link_adapter(struct ap_matrix_mdev *matrix_mdev,
> +				      unsigned long apid)
> +{
> +	unsigned long apqi;
> +
> +	for_each_set_bit_inv(apqi, matrix_mdev->matrix.aqm, AP_DOMAINS)
> +		vfio_ap_mdev_link_apqn(matrix_mdev,
> +				       AP_MKQID(apid, apqi));
> +}
> +
>  /**
>   * assign_adapter_store
>   *
> @@ -622,6 +650,7 @@ static ssize_t assign_adapter_store(struct device *dev,
>  	if (ret)
>  		goto share_err;
>  
> +	vfio_ap_mdev_link_adapter(matrix_mdev, apid);
>  	ret = count;
>  	goto done;
>  
> @@ -634,6 +663,15 @@ static ssize_t assign_adapter_store(struct device *dev,
>  }
>  static DEVICE_ATTR_WO(assign_adapter);
>  
> +static void vfio_ap_mdev_unlink_adapter(struct ap_matrix_mdev *matrix_mdev,
> +					unsigned long apid)
> +{
> +	unsigned long apqi;
> +
> +	for_each_set_bit_inv(apqi, matrix_mdev->matrix.aqm, AP_DOMAINS)
> +		vfio_ap_mdev_unlink_apqn(AP_MKQID(apid, apqi));
> +}
> +
>  /**
>   * unassign_adapter_store
>   *
> @@ -673,6 +711,7 @@ 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_unlink_adapter(matrix_mdev, apid);
>  	mutex_unlock(&matrix_dev->lock);
>  
>  	return count;
> @@ -699,6 +738,15 @@ vfio_ap_mdev_verify_queues_reserved_for_apqi(struct ap_matrix_mdev *matrix_mdev,
>  	return 0;
>  }
>  
> +static void vfio_ap_mdev_link_domain(struct ap_matrix_mdev *matrix_mdev,
> +				     unsigned long apqi)
> +{
> +	unsigned long apid;
> +
> +	for_each_set_bit_inv(apid, matrix_mdev->matrix.apm, AP_DEVICES)
> +		vfio_ap_mdev_link_apqn(matrix_mdev, AP_MKQID(apid, apqi));
> +}
> +
>  /**
>   * assign_domain_store
>   *
> @@ -763,6 +811,7 @@ static ssize_t assign_domain_store(struct device *dev,
>  	if (ret)
>  		goto share_err;
>  
> +	vfio_ap_mdev_link_domain(matrix_mdev, apqi);
>  	ret = count;
>  	goto done;
>  
> @@ -775,6 +824,14 @@ static ssize_t assign_domain_store(struct device *dev,
>  }
>  static DEVICE_ATTR_WO(assign_domain);
>  
> +static void vfio_ap_mdev_unlink_domain(struct ap_matrix_mdev *matrix_mdev,
> +				       unsigned long apqi)
> +{
> +	unsigned long apid;
> +
> +	for_each_set_bit_inv(apid, matrix_mdev->matrix.apm, AP_DEVICES)
> +		vfio_ap_mdev_unlink_apqn(AP_MKQID(apid, apqi));
> +}
>  
>  /**
>   * unassign_domain_store
> @@ -815,6 +872,7 @@ 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_unlink_domain(matrix_mdev, apqi);
>  	mutex_unlock(&matrix_dev->lock);
>  
>  	return count;
> @@ -1317,6 +1375,28 @@ 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)) {
> +			vfio_ap_mdev_link_queue(matrix_mdev, q);
> +			break;
> +		}
> +	}
> +}
> +
>  int vfio_ap_mdev_probe_queue(struct ap_device *apdev)
>  {
>  	struct vfio_ap_queue *q;
> @@ -1324,9 +1404,13 @@ 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);
> +

Does the critical section have to include more than just
vfio_ap_queue_link_mdev()? Did we need the critical section
before this patch?

>  	return 0;
>  }
>  
> @@ -1341,6 +1425,10 @@ 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);
> +
> +	if (q->matrix_mdev)
> +		vfio_ap_mdev_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);