[PATCH v5 3/7] vfio: ap: register IOMMU VFIO notifier

[Pierre Morel <pmorel@xxxxxxxxxxxxx>]

To be able to use the VFIO interface to facilitate the
mediated device memory pinning/unpinning we need to register
a notifier for IOMMU.

While we will start to pin one guest page for the interrupt indicator
byte, this is still ok with ballooning as this page will never be
used by the guest virtio-balloon driver.
So the pinned page will never be freed. And even a broken guest does
so, that would not impact the host as the original page is still
in control by vfio.

Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
Reviewed-by: Cornelia Huck <cohuck@xxxxxxxxxx>
---
 drivers/s390/crypto/vfio_ap_ops.c     | 53 ++++++++++++++++++++++++++++++++---
 drivers/s390/crypto/vfio_ap_private.h |  2 ++
 2 files changed, 51 insertions(+), 4 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index 485595c..0f8952c23 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -757,6 +757,36 @@ static const struct attribute_group *vfio_ap_mdev_attr_groups[] = {
 };
 
 /**
+ * vfio_ap_mdev_iommu_notifier: IOMMU notifier callback
+ *
+ * @nb: The notifier block
+ * @action: Action to be taken
+ * @data: data associated with the request
+ *
+ * For an UNMAP request, unpin the guest IOVA (the NIB guest address we
+ * pinned before). Other requests are ignored.
+ *
+ */
+static int vfio_ap_mdev_iommu_notifier(struct notifier_block *nb,
+				       unsigned long action, void *data)
+{
+	struct ap_matrix_mdev *matrix_mdev;
+
+	matrix_mdev = container_of(nb, struct ap_matrix_mdev, iommu_notifier);
+
+	if (action == VFIO_IOMMU_NOTIFY_DMA_UNMAP) {
+		struct vfio_iommu_type1_dma_unmap *unmap = data;
+		unsigned long g_pfn = unmap->iova >> PAGE_SHIFT;
+
+		vfio_unpin_pages(mdev_dev(matrix_mdev->mdev), &g_pfn, 1);
+		return NOTIFY_OK;
+	}
+
+	return NOTIFY_DONE;
+}
+
+
+/**
  * vfio_ap_mdev_set_kvm
  *
  * @matrix_mdev: a mediated matrix device
@@ -855,12 +885,25 @@ static int vfio_ap_mdev_open(struct mdev_device *mdev)
 
 	ret = vfio_register_notifier(mdev_dev(mdev), VFIO_GROUP_NOTIFY,
 				     &events, &matrix_mdev->group_notifier);
-	if (ret) {
-		module_put(THIS_MODULE);
-		return ret;
-	}
+	if (ret)
+		goto err_group;
+
+	matrix_mdev->iommu_notifier.notifier_call = vfio_ap_mdev_iommu_notifier;
+	events = VFIO_IOMMU_NOTIFY_DMA_UNMAP;
+
+	ret = vfio_register_notifier(mdev_dev(mdev), VFIO_IOMMU_NOTIFY,
+				     &events, &matrix_mdev->iommu_notifier);
+	if (ret)
+		goto err_iommu;
 
 	return 0;
+
+err_iommu:
+	vfio_unregister_notifier(mdev_dev(mdev), VFIO_GROUP_NOTIFY,
+				 &matrix_mdev->group_notifier);
+err_group:
+	module_put(THIS_MODULE);
+	return ret;
 }
 
 static void vfio_ap_mdev_release(struct mdev_device *mdev)
@@ -872,6 +915,8 @@ static void vfio_ap_mdev_release(struct mdev_device *mdev)
 
 	matrix_mdev->kvm = NULL;
 	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);
 	module_put(THIS_MODULE);
diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
index 3e6940c..4a287c8 100644
--- a/drivers/s390/crypto/vfio_ap_private.h
+++ b/drivers/s390/crypto/vfio_ap_private.h
@@ -82,9 +82,11 @@ struct ap_matrix_mdev {
 	struct list_head node;
 	struct ap_matrix matrix;
 	struct notifier_block group_notifier;
+	struct notifier_block iommu_notifier;
 	struct kvm *kvm;
 	struct kvm_s390_module_hook pqap_hook;
 	struct list_head qlist;
+	struct mdev_device *mdev;
 };
 
 extern int vfio_ap_mdev_register(void);
-- 
2.7.4