linux-kernel - Re: [PATCH v4 6/7] s390: ap: Cleanup on removing the AP device

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Date:   Fri, 8 Mar 2019 17:43:45 -0500
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 v4 6/7] s390: ap: Cleanup on removing the AP device

On 2/22/19 10:29 AM, Pierre Morel wrote:
> When the device is remove, we must make sure to
> clear the interruption and reset the AP device.
> 
> We also need to clear the CRYCB of the guest.
> 
> Signed-off-by: Pierre Morel <pmorel@...ux.ibm.com>
> ---
>   drivers/s390/crypto/vfio_ap_drv.c     | 35 +++++++++++++++++++++++++++++++++++
>   drivers/s390/crypto/vfio_ap_ops.c     |  3 ++-
>   drivers/s390/crypto/vfio_ap_private.h |  3 +++
>   3 files changed, 40 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/s390/crypto/vfio_ap_drv.c b/drivers/s390/crypto/vfio_ap_drv.c
> index eca0ffc..e5d91ff 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>
> @@ -12,6 +13,8 @@
>   #include <linux/slab.h>
>   #include <linux/string.h>
>   #include <asm/facility.h>
> +#include <linux/bitops.h>
> +#include <linux/kvm_host.h>
>   #include "vfio_ap_private.h"
>   
>   #define VFIO_AP_ROOT_NAME "vfio_ap"
> @@ -61,6 +64,33 @@ static int vfio_ap_queue_dev_probe(struct ap_device *apdev)
>   }
>   
>   /**
> + * vfio_ap_update_crycb
> + * @q: A pointer to the queue being removed
> + *
> + * We clear the APID of the queue, making this queue unusable for the guest.
> + * After this function we can reset the queue without to fear a race with
> + * the guest to access the queue again.
> + * We do not fear race with the host as we still get the device.
> + */
> +static void vfio_ap_update_crycb(struct vfio_ap_queue *q)
> +{
> +	struct ap_matrix_mdev *matrix_mdev = q->matrix_mdev;
> +
> +	if (!matrix_mdev)
> +		return;
> +
> +	clear_bit_inv(AP_QID_CARD(q->apqn), matrix_mdev->matrix.apm);
> +
> +	if (!matrix_mdev->kvm)
> +		return;
> +
> +	kvm_arch_crypto_set_masks(matrix_mdev->kvm,
> +				  matrix_mdev->matrix.apm,
> +				  matrix_mdev->matrix.aqm,
> +				  matrix_mdev->matrix.adm);
> +}
> +
> +/**
>    * vfio_ap_queue_dev_remove:
>    *
>    * Free the associated vfio_ap_queue structure
> @@ -70,6 +100,11 @@ static void vfio_ap_queue_dev_remove(struct ap_device *apdev)
>   	struct vfio_ap_queue *q;
>   
>   	q = dev_get_drvdata(&apdev->device);
> +	if (!q)
> +		return;
> +
> +	vfio_ap_update_crycb(q);
> +	vfio_ap_mdev_reset_queue(q);

Since the bit corresponding to the APID is cleared in the
vfio_ap_update_crycb() above, shouldn't all queues on that
card also be reset?

>   	list_del(&q->list);
>   	kfree(q);
>   }
> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
> index 0196065..5b9bb33 100644
> --- a/drivers/s390/crypto/vfio_ap_ops.c
> +++ b/drivers/s390/crypto/vfio_ap_ops.c
> @@ -59,6 +59,7 @@ int vfio_ap_mdev_reset_queue(struct vfio_ap_queue *q)
>   			if (retry <= 0)
>   				pr_warn("%s: queue 0x%04x not empty\n",
>   					__func__, q->apqn);
> +			vfio_ap_free_irq(q);

Shouldn't this be done for the response codes that terminate this loop
such as those caught by the default case?

>   			return 0;
>   		case AP_RESPONSE_RESET_IN_PROGRESS:
>   		case AP_RESPONSE_BUSY:
> @@ -83,7 +84,7 @@ int vfio_ap_mdev_reset_queue(struct vfio_ap_queue *q)
>    * Unregister the ISC from the GIB alert
>    * Clear the vfio_ap_queue intern fields
>    */
> -static void vfio_ap_free_irq(struct vfio_ap_queue *q)
> +void vfio_ap_free_irq(struct vfio_ap_queue *q)
>   {
>   	if (!q)
>   		return;
> diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
> index e2fd2c0..cc18215 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
>    */
> @@ -98,4 +99,6 @@ struct vfio_ap_queue {
>   	int	apqn;
>   	unsigned char isc;
>   };
> +void vfio_ap_free_irq(struct vfio_ap_queue *q);
> +int vfio_ap_mdev_reset_queue(struct vfio_ap_queue *q);
>   #endif /* _VFIO_AP_PRIVATE_H_ */
>