Re: [PATCH v5 4/7] s390: ap: setup relation betwen KVM and mediated device

[Halil Pasic <pasic@linux.ibm.com>]

On Wed, 13 Mar 2019 17:05:01 +0100
Pierre Morel <pmorel@linux.ibm.com> wrote:

> When the mediated device is open we setup the relation with KVM unset it
> when the mediated device is released.
> 
> We ensure KVM is present on opening of the mediated device.
> 
> We ensure that KVM survives the mediated device, and establish a direct

survives? 

> link from KVM to the mediated device to simplify the relationship.
> 
> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> ---
>  drivers/s390/crypto/vfio_ap_ops.c | 80 ++++++++++++++++++++++-----------------
>  1 file changed, 46 insertions(+), 34 deletions(-)
> 
> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
> index 0f8952c23..6b559ca 100644
> --- a/drivers/s390/crypto/vfio_ap_ops.c
> +++ b/drivers/s390/crypto/vfio_ap_ops.c
> @@ -790,7 +790,6 @@ static int vfio_ap_mdev_iommu_notifier(struct notifier_block *nb,
>   * vfio_ap_mdev_set_kvm
>   *
>   * @matrix_mdev: a mediated matrix device
> - * @kvm: reference to KVM instance
>   *
>   * Verifies no other mediated matrix device has @kvm and sets a reference to
>   * it in @matrix_mdev->kvm.
> @@ -798,53 +797,39 @@ static int vfio_ap_mdev_iommu_notifier(struct notifier_block *nb,
>   * Return 0 if no other mediated matrix device has a reference to @kvm;
>   * otherwise, returns an -EPERM.
>   */
> -static int vfio_ap_mdev_set_kvm(struct ap_matrix_mdev *matrix_mdev,
> -				struct kvm *kvm)
> +static int vfio_ap_mdev_set_kvm(struct ap_matrix_mdev *matrix_mdev)
>  {
> -	struct ap_matrix_mdev *m;
> -
>  	mutex_lock(&matrix_dev->lock);
> +	if (matrix_mdev->kvm->arch.crypto.pqap_hook)
> +		goto err_unlock;
>  
> -	list_for_each_entry(m, &matrix_dev->mdev_list, node) {
> -		if ((m != matrix_mdev) && (m->kvm == kvm)) {
> -			mutex_unlock(&matrix_dev->lock);
> -			return -EPERM;
> -		}
> -	}
> +	if (!matrix_mdev->kvm->arch.crypto.crycbd)
> +		goto err_unlock;
>  
> -	matrix_mdev->kvm = kvm;
> -	mutex_unlock(&matrix_dev->lock);
> +	matrix_mdev->kvm->arch.crypto.pqap_hook = &matrix_mdev->pqap_hook;
>  
> +	kvm_arch_crypto_set_masks(matrix_mdev->kvm, matrix_mdev->matrix.apm,
> +				  matrix_mdev->matrix.aqm,
> +				  matrix_mdev->matrix.adm);
> +	kvm_get_kvm(matrix_mdev->kvm);
> +	mutex_unlock(&matrix_dev->lock);
>  	return 0;
> +
> +err_unlock:
> +	mutex_unlock(&matrix_dev->lock);
> +	return -EPERM;
>  }
>  
>  static int vfio_ap_mdev_group_notifier(struct notifier_block *nb,
>  				       unsigned long action, void *data)
>  {
> -	int ret;
>  	struct ap_matrix_mdev *matrix_mdev;
>  
>  	if (action != VFIO_GROUP_NOTIFY_SET_KVM)
>  		return NOTIFY_OK;
>  
>  	matrix_mdev = container_of(nb, struct ap_matrix_mdev, group_notifier);
> -
> -	if (!data) {
> -		matrix_mdev->kvm = NULL;
> -		return NOTIFY_OK;
> -	}
> -
> -	ret = vfio_ap_mdev_set_kvm(matrix_mdev, data);
> -	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)
> -		return NOTIFY_DONE;
> -
> -	kvm_arch_crypto_set_masks(matrix_mdev->kvm, matrix_mdev->matrix.apm,
> -				  matrix_mdev->matrix.aqm,
> -				  matrix_mdev->matrix.adm);
> +	matrix_mdev->kvm = data;
>  
>  	return NOTIFY_OK;
>  }
> @@ -888,6 +873,12 @@ static int vfio_ap_mdev_open(struct mdev_device *mdev)
>  	if (ret)
>  		goto err_group;
>  
> +	/* We do not support opening the mediated device without KVM */
> +	if (!matrix_mdev->kvm) {
> +		ret = -ENODEV;
> +		goto err_group;
> +	}
> +
>  	matrix_mdev->iommu_notifier.notifier_call = vfio_ap_mdev_iommu_notifier;
>  	events = VFIO_IOMMU_NOTIFY_DMA_UNMAP;
>  
> @@ -896,8 +887,15 @@ static int vfio_ap_mdev_open(struct mdev_device *mdev)
>  	if (ret)
>  		goto err_iommu;
>  
> +	ret = vfio_ap_mdev_set_kvm(matrix_mdev);

At this point the matrix_mdev->kvm ain't guaranteed to be valid IMHO. Or
am I wrong? If I'm right kvm_get_kvm(matrix_mdev->kvm) could be too late.

> +	if (ret)
> +		goto err_kvm;
> +
>  	return 0;
>  
> +err_kvm:
> +	vfio_unregister_notifier(mdev_dev(mdev), VFIO_IOMMU_NOTIFY,
> +				 &matrix_mdev->iommu_notifier);
>  err_iommu:
>  	vfio_unregister_notifier(mdev_dev(mdev), VFIO_GROUP_NOTIFY,
>  				 &matrix_mdev->group_notifier);
> @@ -906,19 +904,33 @@ static int vfio_ap_mdev_open(struct mdev_device *mdev)
>  	return ret;
>  }
>  
> -static void vfio_ap_mdev_release(struct mdev_device *mdev)
> +static int vfio_ap_mdev_unset_kvm(struct ap_matrix_mdev *matrix_mdev)
>  {
> -	struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
> +	struct kvm *kvm = matrix_mdev->kvm;
>  
>  	if (matrix_mdev->kvm)
>  		kvm_arch_crypto_clear_masks(matrix_mdev->kvm);

This still conditional?

> -
> +	vfio_ap_mdev_reset_queues(matrix_mdev->mdev);

I guess your intention was to move vfio_ap_mdev_reset_queues()
here from vfio_ap_mdev_release(), but you still have a
vfio_ap_mdev_reset_queues() call in vfio_ap_mdev_release().

> +	matrix_mdev->kvm->arch.crypto.pqap_hook = NULL;
>  	matrix_mdev->kvm = NULL;
> +
> +	kvm_put_kvm(kvm);
> +	return 0;
> +}
> +
> +static void vfio_ap_mdev_release(struct mdev_device *mdev)
> +{
> +	struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
> +
> +	mutex_lock(&matrix_dev->lock);
> +
>  	vfio_ap_mdev_reset_queues(mdev);

Here.

Regards,
Halil

> +	vfio_ap_mdev_unset_kvm(matrix_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);
> +	mutex_unlock(&matrix_dev->lock);
>  	module_put(THIS_MODULE);
>  }
>