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

[Pierre Morel <pmorel@xxxxxxxxxxxxx>]

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
link from KVM to the mediated device to simplify the relationship.

Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
---
 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);
+	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);
-
+	vfio_ap_mdev_reset_queues(matrix_mdev->mdev);
+	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);
+	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);
 }
 
-- 
2.7.4