Message-ID: <606e0b66-adca-15b4-c8a9-804056fc11e5@linux.ibm.com>
Date:   Mon, 14 Dec 2020 18:32:50 -0500
From:   Tony Krowiak <akrowiak@...ux.ibm.com>
To:     Halil Pasic <pasic@...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 11/26/20 9:45 AM, Halil Pasic wrote:
> 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);
> +}

I agree because of the case you made below.

>
>> +
>> +/**
>> + * 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?

This line of code was not modified from what is upstream, so I don't
think this patch or even this patch series is the appropriate place to
question this. If you feel strongly that we shouldn't reset the queue
when it is unbound from the vfio_ap device driver, we can discuss
that offline and create an individual patch specifically for that
purpose.

>
>> -	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.

Actually, it belongs in patch 01/14 but I agree, it does not belong
in this 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()?

The kvm_get_kvm() is in the group notifier callback, but it definitely
doesn't belong here with this patch.

>
>> +		}
>> +		hash_del(&q->mdev_qnode);
>> +		q->matrix_mdev = NULL;
> This shouuld be an unlink_queue(q).

Okay.

>
>> +	}
>>   	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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