Re: [PATCH v2 2/7] s390: vfio-ap: maintain a shadow of the guest's CRYCB

[Pierre Morel <pmorel@linux.ibm.com>]

On 03/05/2019 23:14, Tony Krowiak wrote:
> This patch introduces a shadow of the CRYCB being used by a guest. This
> will enable to more effectively manage dynamic changes to the AP
> resources installed on the host that may be assigned to an mdev device
> and being used by a guest. For example:
> 
> * AP adapter cards can be dynamically added to and removed from the AP
>    configuration via the SE or an SCLP command.
> 
> * AP resources that disappear and reappear due to hardware malfunctions.
> 
> * AP queues bound to and unbound from the vfio_ap device driver by a
>    root user.
> 
> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
> ---
>   drivers/s390/crypto/vfio_ap_ops.c     | 91 ++++++++++++++++++++++++++++++++---
>   drivers/s390/crypto/vfio_ap_private.h |  2 +
>   2 files changed, 87 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
> index b88a2a2ba075..44a04b4aa9ae 100644
> --- a/drivers/s390/crypto/vfio_ap_ops.c
> +++ b/drivers/s390/crypto/vfio_ap_ops.c
> @@ -297,6 +297,45 @@ static void vfio_ap_mdev_wait_for_qempty(unsigned long apid, unsigned long apqi)
>   	} while (--retry);
>   }
>   
> +/*
> + * vfio_ap_mdev_update_crycb
> + *
> + * @matrix_mdev: the mediated matrix device
> + *
> + * Updates the AP matrix in the guest's CRYCB from it's shadow masks.
> + *
> + * Returns zero if the guest's CRYCB is successfully updated; otherwise,
> + * returns -ENODEV if a guest is not running or does not have a CRYCB.
> + */
> +static int vfio_ap_mdev_update_crycb(struct ap_matrix_mdev *matrix_mdev)
> +{
> +	if (!matrix_mdev->kvm || !matrix_mdev->kvm->arch.crypto.crycbd)
> +		return -ENODEV;
> +
> +	kvm_arch_crypto_set_masks(matrix_mdev->kvm,
> +				  matrix_mdev->shadow_crycb->apm,
> +				  matrix_mdev->shadow_crycb->aqm,
> +				  matrix_mdev->shadow_crycb->adm);
> +
> +	return 0;
> +}
> +
> +static int match_apqn(struct device *dev, void *data)
> +{
> +	struct ap_queue *apq = to_ap_queue(dev);
> +
> +	return (apq->qid == *(unsigned long *)(data)) ? 1 : 0;
> +}
> +
> +static struct device *vfio_ap_get_queue_dev(unsigned long apid,
> +					     unsigned long apqi)
> +{
> +	unsigned long apqn = AP_MKQID(apid, apqi);
> +
> +	return driver_find_device(&matrix_dev->vfio_ap_drv->driver, NULL,
> +				  &apqn, match_apqn);
> +}
> +
>   /**
>    * assign_adapter_store
>    *
> @@ -805,14 +844,9 @@ static int vfio_ap_mdev_group_notifier(struct notifier_block *nb,
>   	if (ret)
>   		return NOTIFY_DONE;
>   
> -	/* If there is no CRYCB pointer, then we can't copy the masks */
> -	if (!matrix_mdev->kvm->arch.crypto.crycbd)
> +	if (vfio_ap_mdev_update_crycb(matrix_mdev))
>   		return NOTIFY_DONE;
>   
> -	kvm_arch_crypto_set_masks(matrix_mdev->kvm, matrix_mdev->matrix.apm,
> -				  matrix_mdev->matrix.aqm,
> -				  matrix_mdev->matrix.adm);
> -
>   	return NOTIFY_OK;
>   }
>   
> @@ -867,12 +901,55 @@ static int vfio_ap_mdev_reset_queues(struct mdev_device *mdev)
>   	return rc;
>   }
>   
> +static int vfio_ap_mdev_create_shadow_crycb(struct ap_matrix_mdev *matrix_mdev)
> +{
> +	unsigned long apid, apqi, domid;
> +	struct device *dev;
> +
> +	matrix_mdev->shadow_crycb = kzalloc(sizeof(*matrix_mdev->shadow_crycb),
> +					    GFP_KERNEL);
> +	if (!matrix_mdev->shadow_crycb)
> +		return -ENOMEM;
> +
> +	vfio_ap_matrix_init(&matrix_dev->info, matrix_mdev->shadow_crycb);
> +
> +	/*
> +	 * Examine each APQN assigned to the mdev device. Set the APID and APQI
> +	 * in the shadow CRYCB if and only if the queue device identified by
> +	 * the APQN is in the configuration.
> +	 */
> +	for_each_set_bit_inv(apid, matrix_mdev->matrix.apm,
> +			     matrix_mdev->matrix.apm_max + 1) {
> +		for_each_set_bit_inv(apqi, matrix_mdev->matrix.aqm,
> +				     matrix_mdev->matrix.aqm_max + 1) {
> +			dev = vfio_ap_get_queue_dev(apid, apqi);
> +			if (dev) {
> +				set_bit_inv(apid,
> +					    matrix_mdev->shadow_crycb->apm);
> +				set_bit_inv(apqi,
> +					    matrix_mdev->shadow_crycb->aqm);
> +				put_device(dev);
> +			}

I think that if we do not find a device here we have a problem.
Don't we?


> +		}
> +	}
> +
> +	/* Set all control domains assigned to the mdev in the shadow CRYCB */
> +	for_each_set_bit_inv(domid, matrix_mdev->matrix.adm,
> +			     matrix_mdev->matrix.adm_max + 1)
> +		set_bit_inv(domid, matrix_mdev->shadow_crycb->adm);
> +
> +	return 0;
> +}
> +
>   static int vfio_ap_mdev_open(struct mdev_device *mdev)
>   {
>   	struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
>   	unsigned long events;
>   	int ret;
>   
> +	ret = vfio_ap_mdev_create_shadow_crycb(matrix_mdev);
> +	if (ret)
> +		return ret;
>   
>   	if (!try_module_get(THIS_MODULE))
>   		return -ENODEV;
> @@ -902,6 +979,8 @@ static void vfio_ap_mdev_release(struct mdev_device *mdev)
>   				 &matrix_mdev->group_notifier);
>   	matrix_mdev->kvm = NULL;
>   	module_put(THIS_MODULE);
> +	kfree(matrix_mdev->shadow_crycb);
> +	matrix_mdev->shadow_crycb = NULL;
>   }
>   
>   static int vfio_ap_mdev_get_device_info(unsigned long arg)
> diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
> index 76b7f98e47e9..e8457aa61976 100644
> --- a/drivers/s390/crypto/vfio_ap_private.h
> +++ b/drivers/s390/crypto/vfio_ap_private.h
> @@ -72,6 +72,7 @@ struct ap_matrix {
>    * @list:	allows the ap_matrix_mdev struct to be added to a list
>    * @matrix:	the adapters, usage domains and control domains assigned to the
>    *		mediated matrix device.
> + * @shadow_crycb: a shadow copy of the crycb in use by a guest
>    * @group_notifier: notifier block used for specifying callback function for
>    *		    handling the VFIO_GROUP_NOTIFY_SET_KVM event
>    * @kvm:	the struct holding guest's state
> @@ -79,6 +80,7 @@ struct ap_matrix {
>   struct ap_matrix_mdev {
>   	struct list_head node;
>   	struct ap_matrix matrix;
> +	struct ap_matrix *shadow_crycb;
>   	struct notifier_block group_notifier;
>   	struct kvm *kvm;
>   };
> 


-- 
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany