Date:   Tue, 4 Jun 2019 15:38:51 -0400
From:   Tony Krowiak <akrowiak@...ux.ibm.com>
To:     Pierre Morel <pmorel@...ux.ibm.com>, borntraeger@...ibm.com
Cc:     alex.williamson@...hat.com, cohuck@...hat.com,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        kvm@...r.kernel.org, frankja@...ux.ibm.com, pasic@...ux.ibm.com,
        david@...hat.com, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com, freude@...ux.ibm.com, mimu@...ux.ibm.com
Subject: Re: [PATCH v9 3/4] s390: ap: implement PAPQ AQIC interception in
 kernel

On 5/21/19 11:34 AM, Pierre Morel wrote:
> We register a AP PQAP instruction hook during the open
> of the mediated device. And unregister it on release.
> 
> During the probe of the AP device, we allocate a vfio_ap_queue
> structure to keep track of the information we need for the
> PQAP/AQIC instruction interception.
> 
> In the AP PQAP instruction hook, if we receive a demand to
> enable IRQs,
> - we retrieve the vfio_ap_queue based on the APQN we receive
>    in REG1,
> - we retrieve the page of the guest address, (NIB), from
>    register REG2
> - we retrieve the mediated device to use the VFIO pinning
>    infrastructure to pin the page of the guest address,
> - we retrieve the pointer to KVM to register the guest ISC
>    and retrieve the host ISC
> - finaly we activate GISA
> 
> If we receive a demand to disable IRQs,
> - we deactivate GISA
> - unregister from the GIB
> - unpin the NIB
> 
> When removing the AP device from the driver the device is
> reseted and this process unregisters the GISA from the GIB,
> and unpins the NIB address then we free the vfio_ap_queue
> structure.
> 
> Signed-off-by: Pierre Morel <pmorel@...ux.ibm.com>

I made a few comments, but it looks sane to me:
Acked-by: Tony Krowiak <akrowiak@...ux.ibm.com>

> ---
>   drivers/s390/crypto/vfio_ap_drv.c     |  34 +++-
>   drivers/s390/crypto/vfio_ap_ops.c     | 336 +++++++++++++++++++++++++++++++++-
>   drivers/s390/crypto/vfio_ap_private.h |  11 ++
>   3 files changed, 374 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/s390/crypto/vfio_ap_drv.c b/drivers/s390/crypto/vfio_ap_drv.c
> index e9824c3..003662a 100644
> --- a/drivers/s390/crypto/vfio_ap_drv.c
> +++ b/drivers/s390/crypto/vfio_ap_drv.c
> @@ -5,6 +5,7 @@
>    * Copyright IBM Corp. 2018
>    *
>    * Author(s): Tony Krowiak <akrowiak@...ux.ibm.com>
> + *	      Pierre Morel <pmorel@...ux.ibm.com>
>    */
>   
>   #include <linux/module.h>
> @@ -40,14 +41,45 @@ static struct ap_device_id ap_queue_ids[] = {
>   
>   MODULE_DEVICE_TABLE(vfio_ap, ap_queue_ids);
>   
> +/**
> + * vfio_ap_queue_dev_probe:
> + *
> + * Allocate a vfio_ap_queue structure and associate it
> + * with the device as driver_data.
> + */
>   static int vfio_ap_queue_dev_probe(struct ap_device *apdev)
>   {
> +	struct vfio_ap_queue *q;
> +
> +	q = kzalloc(sizeof(*q), GFP_KERNEL);
> +	if (!q)
> +		return -ENOMEM;
> +	dev_set_drvdata(&apdev->device, q);
> +	q->apqn = to_ap_queue(&apdev->device)->qid;
> +	q->saved_isc = VFIO_AP_ISC_INVALID;
>   	return 0;
>   }
>   
> +/**
> + * vfio_ap_queue_dev_remove:
> + *
> + * Takes the matrix lock to avoid actions on this device while removing
> + * Free the associated vfio_ap_queue structure
> + */
>   static void vfio_ap_queue_dev_remove(struct ap_device *apdev)
>   {
> -	/* Nothing to do yet */
> +	struct vfio_ap_queue *q;
> +	int apid, apqi;
> +
> +	mutex_lock(&matrix_dev->lock);
> +	q = dev_get_drvdata(&apdev->device);
> +	dev_set_drvdata(&apdev->device, NULL);
> +	apid = AP_QID_CARD(q->apqn);
> +	apqi = AP_QID_QUEUE(q->apqn);
> +	vfio_ap_mdev_reset_queue(apid, apqi, 1);
> +	vfio_ap_irq_disable(q);
> +	kfree(q);
> +	mutex_unlock(&matrix_dev->lock);
>   }
>   
>   static void vfio_ap_matrix_dev_release(struct device *dev)
> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
> index e8e87bf..015174f 100644
> --- a/drivers/s390/crypto/vfio_ap_ops.c
> +++ b/drivers/s390/crypto/vfio_ap_ops.c
> @@ -24,6 +24,295 @@
>   #define VFIO_AP_MDEV_TYPE_HWVIRT "passthrough"
>   #define VFIO_AP_MDEV_NAME_HWVIRT "VFIO AP Passthrough Device"
>   
> +static int vfio_ap_mdev_reset_queues(struct mdev_device *mdev);
> +
> +static int match_apqn(struct device *dev, void *data)
> +{
> +	struct vfio_ap_queue *q = dev_get_drvdata(dev);
> +
> +	return (q->apqn == *(int *)(data)) ? 1 : 0;
> +}
> +
> +/**
> + * 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
> + */
> +struct vfio_ap_queue *vfio_ap_get_queue(struct ap_matrix_mdev *matrix_mdev,
> +					int apqn)
> +{
> +	struct vfio_ap_queue *q;
> +	struct device *dev;
> +
> +	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;
> +
> +	dev = driver_find_device(&matrix_dev->vfio_ap_drv->driver, NULL,
> +				 &apqn, match_apqn);
> +	if (!dev)
> +		return NULL;
> +	q = dev_get_drvdata(dev);
> +	q->matrix_mdev = matrix_mdev;
> +	put_device(dev);
> +
> +	return q;
> +}
> +
> +/**
> + * vfio_ap_wait_for_irqclear
> + * @apqn: The AP Queue number
> + *
> + * Checks the IRQ bit for the status of this APQN using ap_tapq.
> + * Returns if the ap_tapq function succedded and the bit is clear.

s/succedded/succeeded/

> + * Returns if ap_tapq function failed with invalid, deconfigured or
> + * checkstopped AP.
> + * Otherwise retries up to 5 times after waiting 20ms.
> + *
> + */
> +static void vfio_ap_wait_for_irqclear(int apqn)
> +{
> +	struct ap_queue_status status;
> +	int retry = 5;
> +
> +	do {
> +		status = ap_tapq(apqn, NULL);
> +		switch (status.response_code) {
> +		case AP_RESPONSE_NORMAL:
> +		case AP_RESPONSE_RESET_IN_PROGRESS:
> +			if (!status.irq_enabled)
> +				return;
> +			/* Fall through */
> +		case AP_RESPONSE_BUSY:
> +			msleep(20);
> +			break;
> +		case AP_RESPONSE_Q_NOT_AVAIL:
> +		case AP_RESPONSE_DECONFIGURED:
> +		case AP_RESPONSE_CHECKSTOPPED:
> +		default:
> +			WARN_ONCE(1, "%s: tapq rc %02x: %04x\n", __func__,
> +				  status.response_code, apqn);
> +			return;

Why not just break out of the loop and just use the WARN_ONCE
outside of the loop?

> +		}
> +	} while (--retry);
> +
> +	WARN_ONCE(1, "%s: tapq rc %02x: %04x could not clear IR bit\n",
> +		  __func__, status.response_code, apqn);
> +}
> +
> +/**
> + * vfio_ap_free_aqic_resources
> + * @q: The vfio_ap_queue
> + *
> + * Unregisters the ISC in the GIB when the saved ISC not invalid.
> + * Unpin the guest's page holding the NIB when it exist.
> + * Reset the saved_pfn and saved_isc to invalid values.
> + * Clear the pointer to the matrix mediated device.
> + *
> + */
> +static void vfio_ap_free_aqic_resources(struct vfio_ap_queue *q)
> +{
> +	if (q->saved_isc != VFIO_AP_ISC_INVALID && q->matrix_mdev)
> +		kvm_s390_gisc_unregister(q->matrix_mdev->kvm, q->saved_isc);
> +	if (q->saved_pfn && q->matrix_mdev)
> +		vfio_unpin_pages(mdev_dev(q->matrix_mdev->mdev),
> +				 &q->saved_pfn, 1);
> +	q->saved_pfn = 0;
> +	q->saved_isc = VFIO_AP_ISC_INVALID;
> +	q->matrix_mdev = NULL;
> +}
> +
> +/**
> + * vfio_ap_irq_disable
> + * @q: The vfio_ap_queue
> + *
> + * Uses ap_aqic to disable the interruption and in case of success, reset
> + * in progress or IRQ disable command already proceeded: calls
> + * vfio_ap_wait_for_irqclear() to check for the IRQ bit to be clear
> + * and calls vfio_ap_free_aqic_resources() to free the resources associated
> + * with the AP interrupt handling.
> + *
> + * In the case the AP is busy, or a reset is in progress,
> + * retries after 20ms, up to 5 times.
> + *
> + * Returns if ap_aqic function failed with invalid, deconfigured or
> + * checkstopped AP.
> + */
> +struct ap_queue_status vfio_ap_irq_disable(struct vfio_ap_queue *q)
> +{
> +	struct ap_qirq_ctrl aqic_gisa = {};
> +	struct ap_queue_status status;
> +	int retries = 5;
> +
> +	do {
> +		status = ap_aqic(q->apqn, aqic_gisa, NULL);
> +		switch (status.response_code) {
> +		case AP_RESPONSE_OTHERWISE_CHANGED:
> +		case AP_RESPONSE_NORMAL:
> +			vfio_ap_wait_for_irqclear(q->apqn);
> +			goto end_free;
> +		case AP_RESPONSE_RESET_IN_PROGRESS:
> +		case AP_RESPONSE_BUSY:
> +			msleep(20);
> +			break;
> +		case AP_RESPONSE_Q_NOT_AVAIL:
> +		case AP_RESPONSE_DECONFIGURED:
> +		case AP_RESPONSE_CHECKSTOPPED:
> +		case AP_RESPONSE_INVALID_ADDRESS:
> +		default:
> +			/* All cases in default means AP not operational */
> +			WARN_ONCE(1, "%s: ap_aqic status %d\n", __func__,
> +				  status.response_code);
> +			goto end_free;

Why not just break out of the loop instead of repeating the WARN_ONCE
message?

> +		}
> +	} while (retries--);
> +
> +	WARN_ONCE(1, "%s: ap_aqic status %d\n", __func__,
> +		  status.response_code);
> +end_free:
> +	vfio_ap_free_aqic_resources(q);
> +	return status;
> +}
> +
> +/**
> + * vfio_ap_setirq: Enable Interruption for a APQN
> + *
> + * @dev: the device associated with the ap_queue
> + * @q:   the vfio_ap_queue holding AQIC parameters
> + *
> + * Pin the NIB saved in *q
> + * Register the guest ISC to GIB interface and retrieve the
> + * host ISC to issue the host side PQAP/AQIC
> + *
> + * Response.status may be set to AP_RESPONSE_INVALID_ADDRESS in case the
> + * vfio_pin_pages failed.
> + *
> + * Otherwise return the ap_queue_status returned by the ap_aqic(),
> + * all retry handling will be done by the guest.
> + */
> +static struct ap_queue_status vfio_ap_irq_enable(struct vfio_ap_queue *q,
> +						 int isc,
> +						 unsigned long nib)
> +{
> +	struct ap_qirq_ctrl aqic_gisa = {};
> +	struct ap_queue_status status = {};
> +	struct kvm_s390_gisa *gisa;
> +	struct kvm *kvm;
> +	unsigned long h_nib, g_pfn, h_pfn;
> +	int ret;
> +
> +	g_pfn = nib >> PAGE_SHIFT;
> +	ret = vfio_pin_pages(mdev_dev(q->matrix_mdev->mdev), &g_pfn, 1,
> +			     IOMMU_READ | IOMMU_WRITE, &h_pfn);
> +	switch (ret) {
> +	case 1:
> +		break;
> +	default:
> +		status.response_code = AP_RESPONSE_INVALID_ADDRESS;
> +		return status;
> +	}
> +
> +	kvm = q->matrix_mdev->kvm;
> +	gisa = kvm->arch.gisa_int.origin;
> +
> +	h_nib = (h_pfn << PAGE_SHIFT) | (nib & ~PAGE_MASK);
> +	aqic_gisa.gisc = isc;
> +	aqic_gisa.isc = kvm_s390_gisc_register(kvm, isc);
> +	aqic_gisa.ir = 1;
> +	aqic_gisa.gisa = (uint64_t)gisa >> 4;
> +
> +	status = ap_aqic(q->apqn, aqic_gisa, (void *)h_nib);
> +	switch (status.response_code) {
> +	case AP_RESPONSE_NORMAL:
> +		/* See if we did clear older IRQ configuration */
> +		vfio_ap_free_aqic_resources(q);
> +		q->saved_pfn = g_pfn;
> +		q->saved_isc = isc;
> +		break;
> +	case AP_RESPONSE_OTHERWISE_CHANGED:
> +		/* We could not modify IRQ setings: clear new configuration */
> +		vfio_unpin_pages(mdev_dev(q->matrix_mdev->mdev), &g_pfn, 1);
> +		kvm_s390_gisc_unregister(kvm, isc);
> +		break;
> +	default:
> +		pr_warn("%s: apqn %04x: response: %02x\n", __func__, q->apqn,
> +			status.response_code);
> +		vfio_ap_irq_disable(q);
> +		break;
> +	}
> +
> +	return status;
> +}
> +
> +/**
> + * handle_pqap: PQAP instruction callback
> + *
> + * @vcpu: The vcpu on which we received the PQAP instruction
> + *
> + * Get the general register contents to initialize internal variables.
> + * REG[0]: APQN
> + * REG[1]: IR and ISC
> + * REG[2]: NIB
> + *
> + * Response.status may be set to following Response Code:
> + * - AP_RESPONSE_Q_NOT_AVAIL: if the queue is not available
> + * - AP_RESPONSE_DECONFIGURED: if the queue is not configured
> + * - AP_RESPONSE_NORMAL (0) : in case of successs
> + *   Check vfio_ap_setirq() and vfio_ap_clrirq() for other possible RC.
> + * We take the matrix_dev lock to ensure serialization on queues and
> + * mediated device access.
> + *
> + * Return 0 if we could handle the request inside KVM.
> + * otherwise, returns -EOPNOTSUPP to let QEMU handle the fault.
> + */
> +static int handle_pqap(struct kvm_vcpu *vcpu)
> +{
> +	uint64_t status;
> +	uint16_t apqn;
> +	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))
> +		return -EOPNOTSUPP;
> +
> +	apqn = vcpu->run->s.regs.gprs[0] & 0xffff;
> +	mutex_lock(&matrix_dev->lock);
> +
> +	if (!vcpu->kvm->arch.crypto.pqap_hook)

Wasn't this already checked in patch 2 prior to calling this
function? In fact, doesn't the hook point to this function?

> +		goto out_unlock;
> +	matrix_mdev = container_of(vcpu->kvm->arch.crypto.pqap_hook,
> +				   struct ap_matrix_mdev, pqap_hook);
> +
> +	q = vfio_ap_get_queue(matrix_mdev, apqn);
> +	if (!q)
> +		goto out_unlock;
> +
> +	status = vcpu->run->s.regs.gprs[1];
> +
> +	/* If IR bit(16) is set we enable the interrupt */
> +	if ((status >> (63 - 16)) & 0x01)
> +		qstatus = vfio_ap_irq_enable(q, status & 0x07,
> +					     vcpu->run->s.regs.gprs[2]);
> +	else
> +		qstatus = vfio_ap_irq_disable(q);
> +
> +out_unlock:
> +	memcpy(&vcpu->run->s.regs.gprs[1], &qstatus, sizeof(qstatus));
> +	vcpu->run->s.regs.gprs[1] >>= 32;
> +	mutex_unlock(&matrix_dev->lock);
> +	return 0;
> +}
> +
>   static void vfio_ap_matrix_init(struct ap_config_info *info,
>   				struct ap_matrix *matrix)
>   {
> @@ -45,8 +334,11 @@ static int vfio_ap_mdev_create(struct kobject *kobj, struct mdev_device *mdev)
>   		return -ENOMEM;
>   	}
>   
> +	matrix_mdev->mdev = mdev;
>   	vfio_ap_matrix_init(&matrix_dev->info, &matrix_mdev->matrix);
>   	mdev_set_drvdata(mdev, matrix_mdev);
> +	matrix_mdev->pqap_hook.hook = handle_pqap;
> +	matrix_mdev->pqap_hook.owner = THIS_MODULE;
>   	mutex_lock(&matrix_dev->lock);
>   	list_add(&matrix_mdev->node, &matrix_dev->mdev_list);
>   	mutex_unlock(&matrix_dev->lock);
> @@ -62,6 +354,7 @@ static int vfio_ap_mdev_remove(struct mdev_device *mdev)
>   		return -EBUSY;
>   
>   	mutex_lock(&matrix_dev->lock);
> +	vfio_ap_mdev_reset_queues(mdev);
>   	list_del(&matrix_mdev->node);
>   	mutex_unlock(&matrix_dev->lock);
>   
> @@ -754,6 +1047,8 @@ static int vfio_ap_mdev_set_kvm(struct ap_matrix_mdev *matrix_mdev,
>   	}
>   
>   	matrix_mdev->kvm = kvm;
> +	kvm_get_kvm(kvm);
> +	kvm->arch.crypto.pqap_hook = &matrix_mdev->pqap_hook;
>   	mutex_unlock(&matrix_dev->lock);
>   
>   	return 0;
> @@ -819,15 +1114,36 @@ static int vfio_ap_mdev_group_notifier(struct notifier_block *nb,
>   	return NOTIFY_OK;
>   }
>   
> -static int vfio_ap_mdev_reset_queue(unsigned int apid, unsigned int apqi,
> -				    unsigned int retry)
> +static void vfio_ap_irq_disable_apqn(int apqn)
> +{
> +	struct device *dev;
> +	struct vfio_ap_queue *q;
> +
> +	dev = driver_find_device(&matrix_dev->vfio_ap_drv->driver, NULL,
> +				 &apqn, match_apqn);
> +	if (dev) {
> +		q = dev_get_drvdata(dev);
> +		vfio_ap_irq_disable(q);
> +		put_device(dev);
> +	}
> +}
> +
> +int vfio_ap_mdev_reset_queue(unsigned int apid, unsigned int apqi,
> +			     unsigned int retry)
>   {
>   	struct ap_queue_status status;
> +	int retry2 = 2;
> +	int apqn = AP_MKQID(apid, apqi);
>   
>   	do {
> -		status = ap_zapq(AP_MKQID(apid, apqi));
> +		status = ap_zapq(apqn);
>   		switch (status.response_code) {
>   		case AP_RESPONSE_NORMAL:
> +			while (!status.queue_empty && retry2--) {
> +				msleep(20);
> +				status = ap_tapq(apqn, NULL);
> +			}
> +			WARN_ON_ONCE(retry <= 0);
>   			return 0;
>   		case AP_RESPONSE_RESET_IN_PROGRESS:
>   		case AP_RESPONSE_BUSY:
> @@ -861,6 +1177,7 @@ static int vfio_ap_mdev_reset_queues(struct mdev_device *mdev)
>   			 */
>   			if (ret)
>   				rc = ret;
> +			vfio_ap_irq_disable_apqn(AP_MKQID(apid, apqi));
>   		}
>   	}
>   
> @@ -904,15 +1221,20 @@ static void vfio_ap_mdev_release(struct mdev_device *mdev)
>   {
>   	struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
>   
> -	if (matrix_mdev->kvm)
> +	mutex_lock(&matrix_dev->lock);
> +	if (matrix_mdev->kvm) {
>   		kvm_arch_crypto_clear_masks(matrix_mdev->kvm);
> +		matrix_mdev->kvm->arch.crypto.pqap_hook = NULL;
> +		vfio_ap_mdev_reset_queues(mdev);
> +		kvm_put_kvm(matrix_mdev->kvm);
> +		matrix_mdev->kvm = NULL;
> +	}
> +	mutex_unlock(&matrix_dev->lock);
>   
> -	vfio_ap_mdev_reset_queues(mdev);
>   	vfio_unregister_notifier(mdev_dev(mdev), VFIO_IOMMU_NOTIFY,
>   				 &matrix_mdev->iommu_notifier);
>   	vfio_unregister_notifier(mdev_dev(mdev), VFIO_GROUP_NOTIFY,
>   				 &matrix_mdev->group_notifier);
> -	matrix_mdev->kvm = NULL;
>   	module_put(THIS_MODULE);
>   }
>   
> @@ -941,6 +1263,7 @@ static ssize_t vfio_ap_mdev_ioctl(struct mdev_device *mdev,
>   {
>   	int ret;
>   
> +	mutex_lock(&matrix_dev->lock);
>   	switch (cmd) {
>   	case VFIO_DEVICE_GET_INFO:
>   		ret = vfio_ap_mdev_get_device_info(arg);
> @@ -952,6 +1275,7 @@ static ssize_t vfio_ap_mdev_ioctl(struct mdev_device *mdev,
>   		ret = -EOPNOTSUPP;
>   		break;
>   	}
> +	mutex_unlock(&matrix_dev->lock);
>   
>   	return ret;
>   }
> diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
> index 18dcc4d..f46dde5 100644
> --- a/drivers/s390/crypto/vfio_ap_private.h
> +++ b/drivers/s390/crypto/vfio_ap_private.h
> @@ -4,6 +4,7 @@
>    *
>    * Author(s): Tony Krowiak <akrowiak@...ux.ibm.com>
>    *	      Halil Pasic <pasic@...ux.ibm.com>
> + *	      Pierre Morel <pmorel@...ux.ibm.com>
>    *
>    * Copyright IBM Corp. 2018
>    */
> @@ -89,5 +90,15 @@ struct ap_matrix_mdev {
>   
>   extern int vfio_ap_mdev_register(void);
>   extern void vfio_ap_mdev_unregister(void);
> +int vfio_ap_mdev_reset_queue(unsigned int apid, unsigned int apqi,
> +			     unsigned int retry);
>   
> +struct vfio_ap_queue {
> +	struct ap_matrix_mdev *matrix_mdev;
> +	unsigned long saved_pfn;
> +	int	apqn;
> +#define VFIO_AP_ISC_INVALID 0xff
> +	unsigned char saved_isc;
> +};
> +struct ap_queue_status vfio_ap_irq_disable(struct vfio_ap_queue *q);
>   #endif /* _VFIO_AP_PRIVATE_H_ */
> 

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