[PATCH 0/2] Remove the VFIO_IOMMU_NOTIFY_DMA_UNMAP notifier

[PATCH 0/2] Remove the VFIO_IOMMU_NOTIFY_DMA_UNMAP notifier

[Jason Gunthorpe]

This is the last notifier toward the drivers, replace it with a simple op
callback in the vfio_device_ops.

Jason Gunthorpe (2):
  vfio: Replace the DMA unmapping notifier with a callback
  vfio: Replace the iommu notifier with a device list

 drivers/gpu/drm/i915/gvt/gvt.h        |   1 -
 drivers/gpu/drm/i915/gvt/kvmgt.c      |  75 +++++-------------
 drivers/s390/cio/vfio_ccw_ops.c       |  41 +++-------
 drivers/s390/cio/vfio_ccw_private.h   |   1 -
 drivers/s390/crypto/vfio_ap_ops.c     |  54 +++----------
 drivers/s390/crypto/vfio_ap_private.h |   3 -
 drivers/vfio/vfio.c                   | 105 +++++---------------------
 drivers/vfio/vfio.h                   |   9 +--
 drivers/vfio/vfio_iommu_type1.c       |  74 ++++++++++--------
 include/linux/vfio.h                  |  21 +-----
 10 files changed, 114 insertions(+), 270 deletions(-)


base-commit: f2906aa863381afb0015a9eb7fefad885d4e5a56
-- 
2.36.1

[Intel-gfx] [PATCH 0/2] Remove the VFIO_IOMMU_NOTIFY_DMA_UNMAP notifier

[Jason Gunthorpe]

This is the last notifier toward the drivers, replace it with a simple op
callback in the vfio_device_ops.

Jason Gunthorpe (2):
  vfio: Replace the DMA unmapping notifier with a callback
  vfio: Replace the iommu notifier with a device list

 drivers/gpu/drm/i915/gvt/gvt.h        |   1 -
 drivers/gpu/drm/i915/gvt/kvmgt.c      |  75 +++++-------------
 drivers/s390/cio/vfio_ccw_ops.c       |  41 +++-------
 drivers/s390/cio/vfio_ccw_private.h   |   1 -
 drivers/s390/crypto/vfio_ap_ops.c     |  54 +++----------
 drivers/s390/crypto/vfio_ap_private.h |   3 -
 drivers/vfio/vfio.c                   | 105 +++++---------------------
 drivers/vfio/vfio.h                   |   9 +--
 drivers/vfio/vfio_iommu_type1.c       |  74 ++++++++++--------
 include/linux/vfio.h                  |  21 +-----
 10 files changed, 114 insertions(+), 270 deletions(-)


base-commit: f2906aa863381afb0015a9eb7fefad885d4e5a56
-- 
2.36.1

[PATCH 1/2] vfio: Replace the DMA unmapping notifier with a callback

[Jason Gunthorpe]

Instead of having drivers register the notifier with explicit code just
have them provide a dma_unmap callback op in their driver ops and rely on
the core code to wire it up.

Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
 drivers/gpu/drm/i915/gvt/gvt.h        |   1 -
 drivers/gpu/drm/i915/gvt/kvmgt.c      |  75 ++++-----------
 drivers/s390/cio/vfio_ccw_ops.c       |  41 ++-------
 drivers/s390/cio/vfio_ccw_private.h   |   1 -
 drivers/s390/crypto/vfio_ap_ops.c     |  54 +++--------
 drivers/s390/crypto/vfio_ap_private.h |   3 -
 drivers/vfio/vfio.c                   | 126 +++++++++-----------------
 drivers/vfio/vfio.h                   |   5 +
 include/linux/vfio.h                  |  21 +----
 9 files changed, 92 insertions(+), 235 deletions(-)

diff --git a/drivers/gpu/drm/i915/gvt/gvt.h b/drivers/gpu/drm/i915/gvt/gvt.h
index aee1a45da74bcb..705689e6401197 100644
--- a/drivers/gpu/drm/i915/gvt/gvt.h
+++ b/drivers/gpu/drm/i915/gvt/gvt.h
@@ -226,7 +226,6 @@ struct intel_vgpu {
 	unsigned long nr_cache_entries;
 	struct mutex cache_lock;
 
-	struct notifier_block iommu_notifier;
 	atomic_t released;
 
 	struct kvm_page_track_notifier_node track_node;
diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
index e2f6c56ab3420c..4000659ad715d4 100644
--- a/drivers/gpu/drm/i915/gvt/kvmgt.c
+++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
@@ -729,34 +729,27 @@ int intel_gvt_set_edid(struct intel_vgpu *vgpu, int port_num)
 	return ret;
 }
 
-static int intel_vgpu_iommu_notifier(struct notifier_block *nb,
-				     unsigned long action, void *data)
+static void intel_vgpu_dma_unmap(struct vfio_device *vfio_dev, u64 iova,
+				 u64 length)
 {
-	struct intel_vgpu *vgpu =
-		container_of(nb, struct intel_vgpu, iommu_notifier);
+	struct intel_vgpu *vgpu = vfio_dev_to_vgpu(vfio_dev);
+	struct gvt_dma *entry;
+	u64 iov_pfn, end_iov_pfn;
 
-	if (action == VFIO_IOMMU_NOTIFY_DMA_UNMAP) {
-		struct vfio_iommu_type1_dma_unmap *unmap = data;
-		struct gvt_dma *entry;
-		unsigned long iov_pfn, end_iov_pfn;
+	iov_pfn = iova >> PAGE_SHIFT;
+	end_iov_pfn = iov_pfn + length / PAGE_SIZE;
 
-		iov_pfn = unmap->iova >> PAGE_SHIFT;
-		end_iov_pfn = iov_pfn + unmap->size / PAGE_SIZE;
+	mutex_lock(&vgpu->cache_lock);
+	for (; iov_pfn < end_iov_pfn; iov_pfn++) {
+		entry = __gvt_cache_find_gfn(vgpu, iov_pfn);
+		if (!entry)
+			continue;
 
-		mutex_lock(&vgpu->cache_lock);
-		for (; iov_pfn < end_iov_pfn; iov_pfn++) {
-			entry = __gvt_cache_find_gfn(vgpu, iov_pfn);
-			if (!entry)
-				continue;
-
-			gvt_dma_unmap_page(vgpu, entry->gfn, entry->dma_addr,
-					   entry->size);
-			__gvt_cache_remove_entry(vgpu, entry);
-		}
-		mutex_unlock(&vgpu->cache_lock);
+		gvt_dma_unmap_page(vgpu, entry->gfn, entry->dma_addr,
+				   entry->size);
+		__gvt_cache_remove_entry(vgpu, entry);
 	}
-
-	return NOTIFY_OK;
+	mutex_unlock(&vgpu->cache_lock);
 }
 
 static bool __kvmgt_vgpu_exist(struct intel_vgpu *vgpu)
@@ -783,36 +776,20 @@ static bool __kvmgt_vgpu_exist(struct intel_vgpu *vgpu)
 static int intel_vgpu_open_device(struct vfio_device *vfio_dev)
 {
 	struct intel_vgpu *vgpu = vfio_dev_to_vgpu(vfio_dev);
-	unsigned long events;
-	int ret;
-
-	vgpu->iommu_notifier.notifier_call = intel_vgpu_iommu_notifier;
 
-	events = VFIO_IOMMU_NOTIFY_DMA_UNMAP;
-	ret = vfio_register_notifier(vfio_dev, VFIO_IOMMU_NOTIFY, &events,
-				     &vgpu->iommu_notifier);
-	if (ret != 0) {
-		gvt_vgpu_err("vfio_register_notifier for iommu failed: %d\n",
-			ret);
-		goto out;
-	}
-
-	ret = -EEXIST;
 	if (vgpu->attached)
-		goto undo_iommu;
+		return -EEXIST;
 
-	ret = -ESRCH;
 	if (!vgpu->vfio_device.kvm ||
 	    vgpu->vfio_device.kvm->mm != current->mm) {
 		gvt_vgpu_err("KVM is required to use Intel vGPU\n");
-		goto undo_iommu;
+		return -ESRCH;
 	}
 
 	kvm_get_kvm(vgpu->vfio_device.kvm);
 
-	ret = -EEXIST;
 	if (__kvmgt_vgpu_exist(vgpu))
-		goto undo_iommu;
+		return -EEXIST;
 
 	vgpu->attached = true;
 
@@ -831,12 +808,6 @@ static int intel_vgpu_open_device(struct vfio_device *vfio_dev)
 
 	atomic_set(&vgpu->released, 0);
 	return 0;
-
-undo_iommu:
-	vfio_unregister_notifier(vfio_dev, VFIO_IOMMU_NOTIFY,
-				 &vgpu->iommu_notifier);
-out:
-	return ret;
 }
 
 static void intel_vgpu_release_msi_eventfd_ctx(struct intel_vgpu *vgpu)
@@ -853,8 +824,6 @@ static void intel_vgpu_release_msi_eventfd_ctx(struct intel_vgpu *vgpu)
 static void intel_vgpu_close_device(struct vfio_device *vfio_dev)
 {
 	struct intel_vgpu *vgpu = vfio_dev_to_vgpu(vfio_dev);
-	struct drm_i915_private *i915 = vgpu->gvt->gt->i915;
-	int ret;
 
 	if (!vgpu->attached)
 		return;
@@ -864,11 +833,6 @@ static void intel_vgpu_close_device(struct vfio_device *vfio_dev)
 
 	intel_gvt_release_vgpu(vgpu);
 
-	ret = vfio_unregister_notifier(&vgpu->vfio_device, VFIO_IOMMU_NOTIFY,
-				       &vgpu->iommu_notifier);
-	drm_WARN(&i915->drm, ret,
-		 "vfio_unregister_notifier for iommu failed: %d\n", ret);
-
 	debugfs_remove(debugfs_lookup(KVMGT_DEBUGFS_FILENAME, vgpu->debugfs));
 
 	kvm_page_track_unregister_notifier(vgpu->vfio_device.kvm,
@@ -1610,6 +1574,7 @@ static const struct vfio_device_ops intel_vgpu_dev_ops = {
 	.write		= intel_vgpu_write,
 	.mmap		= intel_vgpu_mmap,
 	.ioctl		= intel_vgpu_ioctl,
+	.dma_unmap	= intel_vgpu_dma_unmap,
 };
 
 static int intel_vgpu_probe(struct mdev_device *mdev)
diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_ops.c
index b49e2e9db2dc6f..d7e3c3ea98518f 100644
--- a/drivers/s390/cio/vfio_ccw_ops.c
+++ b/drivers/s390/cio/vfio_ccw_ops.c
@@ -44,31 +44,19 @@ static int vfio_ccw_mdev_reset(struct vfio_ccw_private *private)
 	return ret;
 }
 
-static int vfio_ccw_mdev_notifier(struct notifier_block *nb,
-				  unsigned long action,
-				  void *data)
+static void vfio_ccw_dma_unmap(struct vfio_device *vdev, u64 iova, u64 length)
 {
 	struct vfio_ccw_private *private =
-		container_of(nb, struct vfio_ccw_private, nb);
-
-	/*
-	 * Vendor drivers MUST unpin pages in response to an
-	 * invalidation.
-	 */
-	if (action == VFIO_IOMMU_NOTIFY_DMA_UNMAP) {
-		struct vfio_iommu_type1_dma_unmap *unmap = data;
-
-		if (!cp_iova_pinned(&private->cp, unmap->iova))
-			return NOTIFY_OK;
+		container_of(vdev, struct vfio_ccw_private, vdev);
 
-		if (vfio_ccw_mdev_reset(private))
-			return NOTIFY_BAD;
+	/* Vendor drivers MUST unpin pages in response to an invalidation. */
+	if (!cp_iova_pinned(&private->cp, iova))
+		return;
 
-		cp_free(&private->cp);
-		return NOTIFY_OK;
-	}
+	if (vfio_ccw_mdev_reset(private))
+		return;
 
-	return NOTIFY_DONE;
+	cp_free(&private->cp);
 }
 
 static ssize_t name_show(struct mdev_type *mtype,
@@ -178,19 +166,11 @@ static int vfio_ccw_mdev_open_device(struct vfio_device *vdev)
 {
 	struct vfio_ccw_private *private =
 		container_of(vdev, struct vfio_ccw_private, vdev);
-	unsigned long events = VFIO_IOMMU_NOTIFY_DMA_UNMAP;
 	int ret;
 
-	private->nb.notifier_call = vfio_ccw_mdev_notifier;
-
-	ret = vfio_register_notifier(vdev, VFIO_IOMMU_NOTIFY,
-				     &events, &private->nb);
-	if (ret)
-		return ret;
-
 	ret = vfio_ccw_register_async_dev_regions(private);
 	if (ret)
-		goto out_unregister;
+		return ret;
 
 	ret = vfio_ccw_register_schib_dev_regions(private);
 	if (ret)
@@ -204,7 +184,6 @@ static int vfio_ccw_mdev_open_device(struct vfio_device *vdev)
 
 out_unregister:
 	vfio_ccw_unregister_dev_regions(private);
-	vfio_unregister_notifier(vdev, VFIO_IOMMU_NOTIFY, &private->nb);
 	return ret;
 }
 
@@ -222,7 +201,6 @@ static void vfio_ccw_mdev_close_device(struct vfio_device *vdev)
 
 	cp_free(&private->cp);
 	vfio_ccw_unregister_dev_regions(private);
-	vfio_unregister_notifier(vdev, VFIO_IOMMU_NOTIFY, &private->nb);
 }
 
 static ssize_t vfio_ccw_mdev_read_io_region(struct vfio_ccw_private *private,
@@ -645,6 +623,7 @@ static const struct vfio_device_ops vfio_ccw_dev_ops = {
 	.write = vfio_ccw_mdev_write,
 	.ioctl = vfio_ccw_mdev_ioctl,
 	.request = vfio_ccw_mdev_request,
+	.dma_unmap = vfio_ccw_dma_unmap,
 };
 
 struct mdev_driver vfio_ccw_mdev_driver = {
diff --git a/drivers/s390/cio/vfio_ccw_private.h b/drivers/s390/cio/vfio_ccw_private.h
index 7272eb78861244..2627791c9006d4 100644
--- a/drivers/s390/cio/vfio_ccw_private.h
+++ b/drivers/s390/cio/vfio_ccw_private.h
@@ -98,7 +98,6 @@ struct vfio_ccw_private {
 	struct completion	*completion;
 	atomic_t		avail;
 	struct mdev_device	*mdev;
-	struct notifier_block	nb;
 	struct ccw_io_region	*io_region;
 	struct mutex		io_mutex;
 	struct vfio_ccw_region *region;
diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index a7d2a95796d360..65b2bd44dd35b8 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -1227,33 +1227,20 @@ static int vfio_ap_mdev_set_kvm(struct ap_matrix_mdev *matrix_mdev,
 }
 
 /**
- * vfio_ap_mdev_iommu_notifier - IOMMU notifier callback
+ * vfio_ap_mdev_dma_unmap - Notifier that IOVA has been unmapped
+ * @vdev: The VFIO device
+ * @unmap: IOVA range unmapped
  *
- * @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.
- *
- * Return: for an UNMAP request, NOFITY_OK; otherwise NOTIFY_DONE.
+ * Unpin the guest IOVA (the NIB guest address we pinned before).
  */
-static int vfio_ap_mdev_iommu_notifier(struct notifier_block *nb,
-				       unsigned long action, void *data)
+static void vfio_ap_mdev_dma_unmap(struct vfio_device *vdev, u64 iova,
+				   u64 length)
 {
-	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(&matrix_mdev->vdev, &g_pfn, 1);
-		return NOTIFY_OK;
-	}
+	struct ap_matrix_mdev *matrix_mdev =
+		container_of(vdev, struct ap_matrix_mdev, vdev);
+	unsigned long g_pfn = iova >> PAGE_SHIFT;
 
-	return NOTIFY_DONE;
+	vfio_unpin_pages(&matrix_mdev->vdev, &g_pfn, 1);
 }
 
 /**
@@ -1380,27 +1367,11 @@ static int vfio_ap_mdev_open_device(struct vfio_device *vdev)
 {
 	struct ap_matrix_mdev *matrix_mdev =
 		container_of(vdev, struct ap_matrix_mdev, vdev);
-	unsigned long events;
-	int ret;
 
 	if (!vdev->kvm)
 		return -EINVAL;
 
-	ret = vfio_ap_mdev_set_kvm(matrix_mdev, vdev->kvm);
-	if (ret)
-		return ret;
-
-	matrix_mdev->iommu_notifier.notifier_call = vfio_ap_mdev_iommu_notifier;
-	events = VFIO_IOMMU_NOTIFY_DMA_UNMAP;
-	ret = vfio_register_notifier(vdev, VFIO_IOMMU_NOTIFY, &events,
-				     &matrix_mdev->iommu_notifier);
-	if (ret)
-		goto err_kvm;
-	return 0;
-
-err_kvm:
-	vfio_ap_mdev_unset_kvm(matrix_mdev);
-	return ret;
+	return vfio_ap_mdev_set_kvm(matrix_mdev, vdev->kvm);
 }
 
 static void vfio_ap_mdev_close_device(struct vfio_device *vdev)
@@ -1408,8 +1379,6 @@ static void vfio_ap_mdev_close_device(struct vfio_device *vdev)
 	struct ap_matrix_mdev *matrix_mdev =
 		container_of(vdev, struct ap_matrix_mdev, vdev);
 
-	vfio_unregister_notifier(vdev, VFIO_IOMMU_NOTIFY,
-				 &matrix_mdev->iommu_notifier);
 	vfio_ap_mdev_unset_kvm(matrix_mdev);
 }
 
@@ -1461,6 +1430,7 @@ static const struct vfio_device_ops vfio_ap_matrix_dev_ops = {
 	.open_device = vfio_ap_mdev_open_device,
 	.close_device = vfio_ap_mdev_close_device,
 	.ioctl = vfio_ap_mdev_ioctl,
+	.dma_unmap = vfio_ap_mdev_dma_unmap,
 };
 
 static struct mdev_driver vfio_ap_matrix_driver = {
diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
index a26efd804d0df3..abb59d59f81b20 100644
--- a/drivers/s390/crypto/vfio_ap_private.h
+++ b/drivers/s390/crypto/vfio_ap_private.h
@@ -81,8 +81,6 @@ struct ap_matrix {
  * @node:	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.
- * @iommu_notifier: notifier block used for specifying callback function for
- *		    handling the VFIO_IOMMU_NOTIFY_DMA_UNMAP even
  * @kvm:	the struct holding guest's state
  * @pqap_hook:	the function pointer to the interception handler for the
  *		PQAP(AQIC) instruction.
@@ -92,7 +90,6 @@ struct ap_matrix_mdev {
 	struct vfio_device vdev;
 	struct list_head node;
 	struct ap_matrix matrix;
-	struct notifier_block iommu_notifier;
 	struct kvm *kvm;
 	crypto_hook pqap_hook;
 	struct mdev_device *mdev;
diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 61e71c1154be67..f005b644ab9e69 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -1077,8 +1077,20 @@ static void vfio_device_unassign_container(struct vfio_device *device)
 	up_write(&device->group->group_rwsem);
 }
 
+static int vfio_iommu_notifier(struct notifier_block *nb, unsigned long action,
+			       void *data)
+{
+	struct vfio_device *vfio_device =
+		container_of(nb, struct vfio_device, iommu_nb);
+	struct vfio_iommu_type1_dma_unmap *unmap = data;
+
+	vfio_device->ops->dma_unmap(vfio_device, unmap->iova, unmap->size);
+	return NOTIFY_OK;
+}
+
 static struct file *vfio_device_open(struct vfio_device *device)
 {
+	struct vfio_iommu_driver *iommu_driver;
 	struct file *filep;
 	int ret;
 
@@ -1109,6 +1121,18 @@ static struct file *vfio_device_open(struct vfio_device *device)
 			if (ret)
 				goto err_undo_count;
 		}
+
+		iommu_driver = device->group->container->iommu_driver;
+		if (device->ops->dma_unmap && iommu_driver &&
+		    iommu_driver->ops->register_notifier) {
+			unsigned long events = VFIO_IOMMU_NOTIFY_DMA_UNMAP;
+
+			device->iommu_nb.notifier_call = vfio_iommu_notifier;
+			iommu_driver->ops->register_notifier(
+				device->group->container->iommu_data, &events,
+				&device->iommu_nb);
+		}
+
 		up_read(&device->group->group_rwsem);
 	}
 	mutex_unlock(&device->dev_set->lock);
@@ -1143,8 +1167,16 @@ static struct file *vfio_device_open(struct vfio_device *device)
 err_close_device:
 	mutex_lock(&device->dev_set->lock);
 	down_read(&device->group->group_rwsem);
-	if (device->open_count == 1 && device->ops->close_device)
+	if (device->open_count == 1 && device->ops->close_device) {
 		device->ops->close_device(device);
+
+		iommu_driver = device->group->container->iommu_driver;
+		if (device->ops->dma_unmap && iommu_driver &&
+		    iommu_driver->ops->register_notifier)
+			iommu_driver->ops->unregister_notifier(
+				device->group->container->iommu_data,
+				&device->iommu_nb);
+	}
 err_undo_count:
 	device->open_count--;
 	if (device->open_count == 0 && device->kvm)
@@ -1339,12 +1371,20 @@ static const struct file_operations vfio_group_fops = {
 static int vfio_device_fops_release(struct inode *inode, struct file *filep)
 {
 	struct vfio_device *device = filep->private_data;
+	struct vfio_iommu_driver *iommu_driver;
 
 	mutex_lock(&device->dev_set->lock);
 	vfio_assert_device_open(device);
 	down_read(&device->group->group_rwsem);
 	if (device->open_count == 1 && device->ops->close_device)
 		device->ops->close_device(device);
+
+	iommu_driver = device->group->container->iommu_driver;
+	if (device->ops->dma_unmap && iommu_driver &&
+	    iommu_driver->ops->register_notifier)
+		iommu_driver->ops->unregister_notifier(
+			device->group->container->iommu_data,
+			&device->iommu_nb);
 	up_read(&device->group->group_rwsem);
 	device->open_count--;
 	if (device->open_count == 0)
@@ -2027,90 +2067,6 @@ int vfio_dma_rw(struct vfio_device *device, dma_addr_t user_iova, void *data,
 }
 EXPORT_SYMBOL(vfio_dma_rw);
 
-static int vfio_register_iommu_notifier(struct vfio_group *group,
-					unsigned long *events,
-					struct notifier_block *nb)
-{
-	struct vfio_container *container;
-	struct vfio_iommu_driver *driver;
-	int ret;
-
-	lockdep_assert_held_read(&group->group_rwsem);
-
-	container = group->container;
-	driver = container->iommu_driver;
-	if (likely(driver && driver->ops->register_notifier))
-		ret = driver->ops->register_notifier(container->iommu_data,
-						     events, nb);
-	else
-		ret = -ENOTTY;
-
-	return ret;
-}
-
-static int vfio_unregister_iommu_notifier(struct vfio_group *group,
-					  struct notifier_block *nb)
-{
-	struct vfio_container *container;
-	struct vfio_iommu_driver *driver;
-	int ret;
-
-	lockdep_assert_held_read(&group->group_rwsem);
-
-	container = group->container;
-	driver = container->iommu_driver;
-	if (likely(driver && driver->ops->unregister_notifier))
-		ret = driver->ops->unregister_notifier(container->iommu_data,
-						       nb);
-	else
-		ret = -ENOTTY;
-
-	return ret;
-}
-
-int vfio_register_notifier(struct vfio_device *device,
-			   enum vfio_notify_type type, unsigned long *events,
-			   struct notifier_block *nb)
-{
-	struct vfio_group *group = device->group;
-	int ret;
-
-	if (!nb || !events || (*events == 0) ||
-	    !vfio_assert_device_open(device))
-		return -EINVAL;
-
-	switch (type) {
-	case VFIO_IOMMU_NOTIFY:
-		ret = vfio_register_iommu_notifier(group, events, nb);
-		break;
-	default:
-		ret = -EINVAL;
-	}
-	return ret;
-}
-EXPORT_SYMBOL(vfio_register_notifier);
-
-int vfio_unregister_notifier(struct vfio_device *device,
-			     enum vfio_notify_type type,
-			     struct notifier_block *nb)
-{
-	struct vfio_group *group = device->group;
-	int ret;
-
-	if (!nb || !vfio_assert_device_open(device))
-		return -EINVAL;
-
-	switch (type) {
-	case VFIO_IOMMU_NOTIFY:
-		ret = vfio_unregister_iommu_notifier(group, nb);
-		break;
-	default:
-		ret = -EINVAL;
-	}
-	return ret;
-}
-EXPORT_SYMBOL(vfio_unregister_notifier);
-
 /*
  * Module/class support
  */
diff --git a/drivers/vfio/vfio.h b/drivers/vfio/vfio.h
index a6713022115155..cb2e4e9baa8fe8 100644
--- a/drivers/vfio/vfio.h
+++ b/drivers/vfio/vfio.h
@@ -33,6 +33,11 @@ enum vfio_iommu_notify_type {
 	VFIO_IOMMU_CONTAINER_CLOSE = 0,
 };
 
+/* events for register_notifier() */
+enum {
+	VFIO_IOMMU_NOTIFY_DMA_UNMAP = 1,
+};
+
 /**
  * struct vfio_iommu_driver_ops - VFIO IOMMU driver callbacks
  */
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index aa888cc517578e..b76623e3b92fca 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -44,6 +44,7 @@ struct vfio_device {
 	unsigned int open_count;
 	struct completion comp;
 	struct list_head group_next;
+	struct notifier_block iommu_nb;
 };
 
 /**
@@ -60,6 +61,8 @@ struct vfio_device {
  * @match: Optional device name match callback (return: 0 for no-match, >0 for
  *         match, -errno for abort (ex. match with insufficient or incorrect
  *         additional args)
+ * @dma_unmap: Called when userspace unmaps IOVA from the container
+ *             this device is attached to.
  * @device_feature: Optional, fill in the VFIO_DEVICE_FEATURE ioctl
  * @migration_set_state: Optional callback to change the migration state for
  *         devices that support migration. It's mandatory for
@@ -85,6 +88,7 @@ struct vfio_device_ops {
 	int	(*mmap)(struct vfio_device *vdev, struct vm_area_struct *vma);
 	void	(*request)(struct vfio_device *vdev, unsigned int count);
 	int	(*match)(struct vfio_device *vdev, char *buf);
+	void	(*dma_unmap)(struct vfio_device *vdev, u64 iova, u64 length);
 	int	(*device_feature)(struct vfio_device *device, u32 flags,
 				  void __user *arg, size_t argsz);
 	struct file *(*migration_set_state)(
@@ -154,23 +158,6 @@ extern int vfio_unpin_pages(struct vfio_device *device, unsigned long *user_pfn,
 extern int vfio_dma_rw(struct vfio_device *device, dma_addr_t user_iova,
 		       void *data, size_t len, bool write);
 
-/* each type has independent events */
-enum vfio_notify_type {
-	VFIO_IOMMU_NOTIFY = 0,
-};
-
-/* events for VFIO_IOMMU_NOTIFY */
-#define VFIO_IOMMU_NOTIFY_DMA_UNMAP	BIT(0)
-
-extern int vfio_register_notifier(struct vfio_device *device,
-				  enum vfio_notify_type type,
-				  unsigned long *required_events,
-				  struct notifier_block *nb);
-extern int vfio_unregister_notifier(struct vfio_device *device,
-				    enum vfio_notify_type type,
-				    struct notifier_block *nb);
-
-
 /*
  * Sub-module helpers
  */
-- 
2.36.1

[Intel-gfx] [PATCH 1/2] vfio: Replace the DMA unmapping notifier with a callback

[Jason Gunthorpe]

Instead of having drivers register the notifier with explicit code just
have them provide a dma_unmap callback op in their driver ops and rely on
the core code to wire it up.

Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
 drivers/gpu/drm/i915/gvt/gvt.h        |   1 -
 drivers/gpu/drm/i915/gvt/kvmgt.c      |  75 ++++-----------
 drivers/s390/cio/vfio_ccw_ops.c       |  41 ++-------
 drivers/s390/cio/vfio_ccw_private.h   |   1 -
 drivers/s390/crypto/vfio_ap_ops.c     |  54 +++--------
 drivers/s390/crypto/vfio_ap_private.h |   3 -
 drivers/vfio/vfio.c                   | 126 +++++++++-----------------
 drivers/vfio/vfio.h                   |   5 +
 include/linux/vfio.h                  |  21 +----
 9 files changed, 92 insertions(+), 235 deletions(-)

diff --git a/drivers/gpu/drm/i915/gvt/gvt.h b/drivers/gpu/drm/i915/gvt/gvt.h
index aee1a45da74bcb..705689e6401197 100644
--- a/drivers/gpu/drm/i915/gvt/gvt.h
+++ b/drivers/gpu/drm/i915/gvt/gvt.h
@@ -226,7 +226,6 @@ struct intel_vgpu {
 	unsigned long nr_cache_entries;
 	struct mutex cache_lock;
 
-	struct notifier_block iommu_notifier;
 	atomic_t released;
 
 	struct kvm_page_track_notifier_node track_node;
diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
index e2f6c56ab3420c..4000659ad715d4 100644
--- a/drivers/gpu/drm/i915/gvt/kvmgt.c
+++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
@@ -729,34 +729,27 @@ int intel_gvt_set_edid(struct intel_vgpu *vgpu, int port_num)
 	return ret;
 }
 
-static int intel_vgpu_iommu_notifier(struct notifier_block *nb,
-				     unsigned long action, void *data)
+static void intel_vgpu_dma_unmap(struct vfio_device *vfio_dev, u64 iova,
+				 u64 length)
 {
-	struct intel_vgpu *vgpu =
-		container_of(nb, struct intel_vgpu, iommu_notifier);
+	struct intel_vgpu *vgpu = vfio_dev_to_vgpu(vfio_dev);
+	struct gvt_dma *entry;
+	u64 iov_pfn, end_iov_pfn;
 
-	if (action == VFIO_IOMMU_NOTIFY_DMA_UNMAP) {
-		struct vfio_iommu_type1_dma_unmap *unmap = data;
-		struct gvt_dma *entry;
-		unsigned long iov_pfn, end_iov_pfn;
+	iov_pfn = iova >> PAGE_SHIFT;
+	end_iov_pfn = iov_pfn + length / PAGE_SIZE;
 
-		iov_pfn = unmap->iova >> PAGE_SHIFT;
-		end_iov_pfn = iov_pfn + unmap->size / PAGE_SIZE;
+	mutex_lock(&vgpu->cache_lock);
+	for (; iov_pfn < end_iov_pfn; iov_pfn++) {
+		entry = __gvt_cache_find_gfn(vgpu, iov_pfn);
+		if (!entry)
+			continue;
 
-		mutex_lock(&vgpu->cache_lock);
-		for (; iov_pfn < end_iov_pfn; iov_pfn++) {
-			entry = __gvt_cache_find_gfn(vgpu, iov_pfn);
-			if (!entry)
-				continue;
-
-			gvt_dma_unmap_page(vgpu, entry->gfn, entry->dma_addr,
-					   entry->size);
-			__gvt_cache_remove_entry(vgpu, entry);
-		}
-		mutex_unlock(&vgpu->cache_lock);
+		gvt_dma_unmap_page(vgpu, entry->gfn, entry->dma_addr,
+				   entry->size);
+		__gvt_cache_remove_entry(vgpu, entry);
 	}
-
-	return NOTIFY_OK;
+	mutex_unlock(&vgpu->cache_lock);
 }
 
 static bool __kvmgt_vgpu_exist(struct intel_vgpu *vgpu)
@@ -783,36 +776,20 @@ static bool __kvmgt_vgpu_exist(struct intel_vgpu *vgpu)
 static int intel_vgpu_open_device(struct vfio_device *vfio_dev)
 {
 	struct intel_vgpu *vgpu = vfio_dev_to_vgpu(vfio_dev);
-	unsigned long events;
-	int ret;
-
-	vgpu->iommu_notifier.notifier_call = intel_vgpu_iommu_notifier;
 
-	events = VFIO_IOMMU_NOTIFY_DMA_UNMAP;
-	ret = vfio_register_notifier(vfio_dev, VFIO_IOMMU_NOTIFY, &events,
-				     &vgpu->iommu_notifier);
-	if (ret != 0) {
-		gvt_vgpu_err("vfio_register_notifier for iommu failed: %d\n",
-			ret);
-		goto out;
-	}
-
-	ret = -EEXIST;
 	if (vgpu->attached)
-		goto undo_iommu;
+		return -EEXIST;
 
-	ret = -ESRCH;
 	if (!vgpu->vfio_device.kvm ||
 	    vgpu->vfio_device.kvm->mm != current->mm) {
 		gvt_vgpu_err("KVM is required to use Intel vGPU\n");
-		goto undo_iommu;
+		return -ESRCH;
 	}
 
 	kvm_get_kvm(vgpu->vfio_device.kvm);
 
-	ret = -EEXIST;
 	if (__kvmgt_vgpu_exist(vgpu))
-		goto undo_iommu;
+		return -EEXIST;
 
 	vgpu->attached = true;
 
@@ -831,12 +808,6 @@ static int intel_vgpu_open_device(struct vfio_device *vfio_dev)
 
 	atomic_set(&vgpu->released, 0);
 	return 0;
-
-undo_iommu:
-	vfio_unregister_notifier(vfio_dev, VFIO_IOMMU_NOTIFY,
-				 &vgpu->iommu_notifier);
-out:
-	return ret;
 }
 
 static void intel_vgpu_release_msi_eventfd_ctx(struct intel_vgpu *vgpu)
@@ -853,8 +824,6 @@ static void intel_vgpu_release_msi_eventfd_ctx(struct intel_vgpu *vgpu)
 static void intel_vgpu_close_device(struct vfio_device *vfio_dev)
 {
 	struct intel_vgpu *vgpu = vfio_dev_to_vgpu(vfio_dev);
-	struct drm_i915_private *i915 = vgpu->gvt->gt->i915;
-	int ret;
 
 	if (!vgpu->attached)
 		return;
@@ -864,11 +833,6 @@ static void intel_vgpu_close_device(struct vfio_device *vfio_dev)
 
 	intel_gvt_release_vgpu(vgpu);
 
-	ret = vfio_unregister_notifier(&vgpu->vfio_device, VFIO_IOMMU_NOTIFY,
-				       &vgpu->iommu_notifier);
-	drm_WARN(&i915->drm, ret,
-		 "vfio_unregister_notifier for iommu failed: %d\n", ret);
-
 	debugfs_remove(debugfs_lookup(KVMGT_DEBUGFS_FILENAME, vgpu->debugfs));
 
 	kvm_page_track_unregister_notifier(vgpu->vfio_device.kvm,
@@ -1610,6 +1574,7 @@ static const struct vfio_device_ops intel_vgpu_dev_ops = {
 	.write		= intel_vgpu_write,
 	.mmap		= intel_vgpu_mmap,
 	.ioctl		= intel_vgpu_ioctl,
+	.dma_unmap	= intel_vgpu_dma_unmap,
 };
 
 static int intel_vgpu_probe(struct mdev_device *mdev)
diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_ops.c
index b49e2e9db2dc6f..d7e3c3ea98518f 100644
--- a/drivers/s390/cio/vfio_ccw_ops.c
+++ b/drivers/s390/cio/vfio_ccw_ops.c
@@ -44,31 +44,19 @@ static int vfio_ccw_mdev_reset(struct vfio_ccw_private *private)
 	return ret;
 }
 
-static int vfio_ccw_mdev_notifier(struct notifier_block *nb,
-				  unsigned long action,
-				  void *data)
+static void vfio_ccw_dma_unmap(struct vfio_device *vdev, u64 iova, u64 length)
 {
 	struct vfio_ccw_private *private =
-		container_of(nb, struct vfio_ccw_private, nb);
-
-	/*
-	 * Vendor drivers MUST unpin pages in response to an
-	 * invalidation.
-	 */
-	if (action == VFIO_IOMMU_NOTIFY_DMA_UNMAP) {
-		struct vfio_iommu_type1_dma_unmap *unmap = data;
-
-		if (!cp_iova_pinned(&private->cp, unmap->iova))
-			return NOTIFY_OK;
+		container_of(vdev, struct vfio_ccw_private, vdev);
 
-		if (vfio_ccw_mdev_reset(private))
-			return NOTIFY_BAD;
+	/* Vendor drivers MUST unpin pages in response to an invalidation. */
+	if (!cp_iova_pinned(&private->cp, iova))
+		return;
 
-		cp_free(&private->cp);
-		return NOTIFY_OK;
-	}
+	if (vfio_ccw_mdev_reset(private))
+		return;
 
-	return NOTIFY_DONE;
+	cp_free(&private->cp);
 }
 
 static ssize_t name_show(struct mdev_type *mtype,
@@ -178,19 +166,11 @@ static int vfio_ccw_mdev_open_device(struct vfio_device *vdev)
 {
 	struct vfio_ccw_private *private =
 		container_of(vdev, struct vfio_ccw_private, vdev);
-	unsigned long events = VFIO_IOMMU_NOTIFY_DMA_UNMAP;
 	int ret;
 
-	private->nb.notifier_call = vfio_ccw_mdev_notifier;
-
-	ret = vfio_register_notifier(vdev, VFIO_IOMMU_NOTIFY,
-				     &events, &private->nb);
-	if (ret)
-		return ret;
-
 	ret = vfio_ccw_register_async_dev_regions(private);
 	if (ret)
-		goto out_unregister;
+		return ret;
 
 	ret = vfio_ccw_register_schib_dev_regions(private);
 	if (ret)
@@ -204,7 +184,6 @@ static int vfio_ccw_mdev_open_device(struct vfio_device *vdev)
 
 out_unregister:
 	vfio_ccw_unregister_dev_regions(private);
-	vfio_unregister_notifier(vdev, VFIO_IOMMU_NOTIFY, &private->nb);
 	return ret;
 }
 
@@ -222,7 +201,6 @@ static void vfio_ccw_mdev_close_device(struct vfio_device *vdev)
 
 	cp_free(&private->cp);
 	vfio_ccw_unregister_dev_regions(private);
-	vfio_unregister_notifier(vdev, VFIO_IOMMU_NOTIFY, &private->nb);
 }
 
 static ssize_t vfio_ccw_mdev_read_io_region(struct vfio_ccw_private *private,
@@ -645,6 +623,7 @@ static const struct vfio_device_ops vfio_ccw_dev_ops = {
 	.write = vfio_ccw_mdev_write,
 	.ioctl = vfio_ccw_mdev_ioctl,
 	.request = vfio_ccw_mdev_request,
+	.dma_unmap = vfio_ccw_dma_unmap,
 };
 
 struct mdev_driver vfio_ccw_mdev_driver = {
diff --git a/drivers/s390/cio/vfio_ccw_private.h b/drivers/s390/cio/vfio_ccw_private.h
index 7272eb78861244..2627791c9006d4 100644
--- a/drivers/s390/cio/vfio_ccw_private.h
+++ b/drivers/s390/cio/vfio_ccw_private.h
@@ -98,7 +98,6 @@ struct vfio_ccw_private {
 	struct completion	*completion;
 	atomic_t		avail;
 	struct mdev_device	*mdev;
-	struct notifier_block	nb;
 	struct ccw_io_region	*io_region;
 	struct mutex		io_mutex;
 	struct vfio_ccw_region *region;
diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index a7d2a95796d360..65b2bd44dd35b8 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -1227,33 +1227,20 @@ static int vfio_ap_mdev_set_kvm(struct ap_matrix_mdev *matrix_mdev,
 }
 
 /**
- * vfio_ap_mdev_iommu_notifier - IOMMU notifier callback
+ * vfio_ap_mdev_dma_unmap - Notifier that IOVA has been unmapped
+ * @vdev: The VFIO device
+ * @unmap: IOVA range unmapped
  *
- * @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.
- *
- * Return: for an UNMAP request, NOFITY_OK; otherwise NOTIFY_DONE.
+ * Unpin the guest IOVA (the NIB guest address we pinned before).
  */
-static int vfio_ap_mdev_iommu_notifier(struct notifier_block *nb,
-				       unsigned long action, void *data)
+static void vfio_ap_mdev_dma_unmap(struct vfio_device *vdev, u64 iova,
+				   u64 length)
 {
-	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(&matrix_mdev->vdev, &g_pfn, 1);
-		return NOTIFY_OK;
-	}
+	struct ap_matrix_mdev *matrix_mdev =
+		container_of(vdev, struct ap_matrix_mdev, vdev);
+	unsigned long g_pfn = iova >> PAGE_SHIFT;
 
-	return NOTIFY_DONE;
+	vfio_unpin_pages(&matrix_mdev->vdev, &g_pfn, 1);
 }
 
 /**
@@ -1380,27 +1367,11 @@ static int vfio_ap_mdev_open_device(struct vfio_device *vdev)
 {
 	struct ap_matrix_mdev *matrix_mdev =
 		container_of(vdev, struct ap_matrix_mdev, vdev);
-	unsigned long events;
-	int ret;
 
 	if (!vdev->kvm)
 		return -EINVAL;
 
-	ret = vfio_ap_mdev_set_kvm(matrix_mdev, vdev->kvm);
-	if (ret)
-		return ret;
-
-	matrix_mdev->iommu_notifier.notifier_call = vfio_ap_mdev_iommu_notifier;
-	events = VFIO_IOMMU_NOTIFY_DMA_UNMAP;
-	ret = vfio_register_notifier(vdev, VFIO_IOMMU_NOTIFY, &events,
-				     &matrix_mdev->iommu_notifier);
-	if (ret)
-		goto err_kvm;
-	return 0;
-
-err_kvm:
-	vfio_ap_mdev_unset_kvm(matrix_mdev);
-	return ret;
+	return vfio_ap_mdev_set_kvm(matrix_mdev, vdev->kvm);
 }
 
 static void vfio_ap_mdev_close_device(struct vfio_device *vdev)
@@ -1408,8 +1379,6 @@ static void vfio_ap_mdev_close_device(struct vfio_device *vdev)
 	struct ap_matrix_mdev *matrix_mdev =
 		container_of(vdev, struct ap_matrix_mdev, vdev);
 
-	vfio_unregister_notifier(vdev, VFIO_IOMMU_NOTIFY,
-				 &matrix_mdev->iommu_notifier);
 	vfio_ap_mdev_unset_kvm(matrix_mdev);
 }
 
@@ -1461,6 +1430,7 @@ static const struct vfio_device_ops vfio_ap_matrix_dev_ops = {
 	.open_device = vfio_ap_mdev_open_device,
 	.close_device = vfio_ap_mdev_close_device,
 	.ioctl = vfio_ap_mdev_ioctl,
+	.dma_unmap = vfio_ap_mdev_dma_unmap,
 };
 
 static struct mdev_driver vfio_ap_matrix_driver = {
diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
index a26efd804d0df3..abb59d59f81b20 100644
--- a/drivers/s390/crypto/vfio_ap_private.h
+++ b/drivers/s390/crypto/vfio_ap_private.h
@@ -81,8 +81,6 @@ struct ap_matrix {
  * @node:	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.
- * @iommu_notifier: notifier block used for specifying callback function for
- *		    handling the VFIO_IOMMU_NOTIFY_DMA_UNMAP even
  * @kvm:	the struct holding guest's state
  * @pqap_hook:	the function pointer to the interception handler for the
  *		PQAP(AQIC) instruction.
@@ -92,7 +90,6 @@ struct ap_matrix_mdev {
 	struct vfio_device vdev;
 	struct list_head node;
 	struct ap_matrix matrix;
-	struct notifier_block iommu_notifier;
 	struct kvm *kvm;
 	crypto_hook pqap_hook;
 	struct mdev_device *mdev;
diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 61e71c1154be67..f005b644ab9e69 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -1077,8 +1077,20 @@ static void vfio_device_unassign_container(struct vfio_device *device)
 	up_write(&device->group->group_rwsem);
 }
 
+static int vfio_iommu_notifier(struct notifier_block *nb, unsigned long action,
+			       void *data)
+{
+	struct vfio_device *vfio_device =
+		container_of(nb, struct vfio_device, iommu_nb);
+	struct vfio_iommu_type1_dma_unmap *unmap = data;
+
+	vfio_device->ops->dma_unmap(vfio_device, unmap->iova, unmap->size);
+	return NOTIFY_OK;
+}
+
 static struct file *vfio_device_open(struct vfio_device *device)
 {
+	struct vfio_iommu_driver *iommu_driver;
 	struct file *filep;
 	int ret;
 
@@ -1109,6 +1121,18 @@ static struct file *vfio_device_open(struct vfio_device *device)
 			if (ret)
 				goto err_undo_count;
 		}
+
+		iommu_driver = device->group->container->iommu_driver;
+		if (device->ops->dma_unmap && iommu_driver &&
+		    iommu_driver->ops->register_notifier) {
+			unsigned long events = VFIO_IOMMU_NOTIFY_DMA_UNMAP;
+
+			device->iommu_nb.notifier_call = vfio_iommu_notifier;
+			iommu_driver->ops->register_notifier(
+				device->group->container->iommu_data, &events,
+				&device->iommu_nb);
+		}
+
 		up_read(&device->group->group_rwsem);
 	}
 	mutex_unlock(&device->dev_set->lock);
@@ -1143,8 +1167,16 @@ static struct file *vfio_device_open(struct vfio_device *device)
 err_close_device:
 	mutex_lock(&device->dev_set->lock);
 	down_read(&device->group->group_rwsem);
-	if (device->open_count == 1 && device->ops->close_device)
+	if (device->open_count == 1 && device->ops->close_device) {
 		device->ops->close_device(device);
+
+		iommu_driver = device->group->container->iommu_driver;
+		if (device->ops->dma_unmap && iommu_driver &&
+		    iommu_driver->ops->register_notifier)
+			iommu_driver->ops->unregister_notifier(
+				device->group->container->iommu_data,
+				&device->iommu_nb);
+	}
 err_undo_count:
 	device->open_count--;
 	if (device->open_count == 0 && device->kvm)
@@ -1339,12 +1371,20 @@ static const struct file_operations vfio_group_fops = {
 static int vfio_device_fops_release(struct inode *inode, struct file *filep)
 {
 	struct vfio_device *device = filep->private_data;
+	struct vfio_iommu_driver *iommu_driver;
 
 	mutex_lock(&device->dev_set->lock);
 	vfio_assert_device_open(device);
 	down_read(&device->group->group_rwsem);
 	if (device->open_count == 1 && device->ops->close_device)
 		device->ops->close_device(device);
+
+	iommu_driver = device->group->container->iommu_driver;
+	if (device->ops->dma_unmap && iommu_driver &&
+	    iommu_driver->ops->register_notifier)
+		iommu_driver->ops->unregister_notifier(
+			device->group->container->iommu_data,
+			&device->iommu_nb);
 	up_read(&device->group->group_rwsem);
 	device->open_count--;
 	if (device->open_count == 0)
@@ -2027,90 +2067,6 @@ int vfio_dma_rw(struct vfio_device *device, dma_addr_t user_iova, void *data,
 }
 EXPORT_SYMBOL(vfio_dma_rw);
 
-static int vfio_register_iommu_notifier(struct vfio_group *group,
-					unsigned long *events,
-					struct notifier_block *nb)
-{
-	struct vfio_container *container;
-	struct vfio_iommu_driver *driver;
-	int ret;
-
-	lockdep_assert_held_read(&group->group_rwsem);
-
-	container = group->container;
-	driver = container->iommu_driver;
-	if (likely(driver && driver->ops->register_notifier))
-		ret = driver->ops->register_notifier(container->iommu_data,
-						     events, nb);
-	else
-		ret = -ENOTTY;
-
-	return ret;
-}
-
-static int vfio_unregister_iommu_notifier(struct vfio_group *group,
-					  struct notifier_block *nb)
-{
-	struct vfio_container *container;
-	struct vfio_iommu_driver *driver;
-	int ret;
-
-	lockdep_assert_held_read(&group->group_rwsem);
-
-	container = group->container;
-	driver = container->iommu_driver;
-	if (likely(driver && driver->ops->unregister_notifier))
-		ret = driver->ops->unregister_notifier(container->iommu_data,
-						       nb);
-	else
-		ret = -ENOTTY;
-
-	return ret;
-}
-
-int vfio_register_notifier(struct vfio_device *device,
-			   enum vfio_notify_type type, unsigned long *events,
-			   struct notifier_block *nb)
-{
-	struct vfio_group *group = device->group;
-	int ret;
-
-	if (!nb || !events || (*events == 0) ||
-	    !vfio_assert_device_open(device))
-		return -EINVAL;
-
-	switch (type) {
-	case VFIO_IOMMU_NOTIFY:
-		ret = vfio_register_iommu_notifier(group, events, nb);
-		break;
-	default:
-		ret = -EINVAL;
-	}
-	return ret;
-}
-EXPORT_SYMBOL(vfio_register_notifier);
-
-int vfio_unregister_notifier(struct vfio_device *device,
-			     enum vfio_notify_type type,
-			     struct notifier_block *nb)
-{
-	struct vfio_group *group = device->group;
-	int ret;
-
-	if (!nb || !vfio_assert_device_open(device))
-		return -EINVAL;
-
-	switch (type) {
-	case VFIO_IOMMU_NOTIFY:
-		ret = vfio_unregister_iommu_notifier(group, nb);
-		break;
-	default:
-		ret = -EINVAL;
-	}
-	return ret;
-}
-EXPORT_SYMBOL(vfio_unregister_notifier);
-
 /*
  * Module/class support
  */
diff --git a/drivers/vfio/vfio.h b/drivers/vfio/vfio.h
index a6713022115155..cb2e4e9baa8fe8 100644
--- a/drivers/vfio/vfio.h
+++ b/drivers/vfio/vfio.h
@@ -33,6 +33,11 @@ enum vfio_iommu_notify_type {
 	VFIO_IOMMU_CONTAINER_CLOSE = 0,
 };
 
+/* events for register_notifier() */
+enum {
+	VFIO_IOMMU_NOTIFY_DMA_UNMAP = 1,
+};
+
 /**
  * struct vfio_iommu_driver_ops - VFIO IOMMU driver callbacks
  */
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index aa888cc517578e..b76623e3b92fca 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -44,6 +44,7 @@ struct vfio_device {
 	unsigned int open_count;
 	struct completion comp;
 	struct list_head group_next;
+	struct notifier_block iommu_nb;
 };
 
 /**
@@ -60,6 +61,8 @@ struct vfio_device {
  * @match: Optional device name match callback (return: 0 for no-match, >0 for
  *         match, -errno for abort (ex. match with insufficient or incorrect
  *         additional args)
+ * @dma_unmap: Called when userspace unmaps IOVA from the container
+ *             this device is attached to.
  * @device_feature: Optional, fill in the VFIO_DEVICE_FEATURE ioctl
  * @migration_set_state: Optional callback to change the migration state for
  *         devices that support migration. It's mandatory for
@@ -85,6 +88,7 @@ struct vfio_device_ops {
 	int	(*mmap)(struct vfio_device *vdev, struct vm_area_struct *vma);
 	void	(*request)(struct vfio_device *vdev, unsigned int count);
 	int	(*match)(struct vfio_device *vdev, char *buf);
+	void	(*dma_unmap)(struct vfio_device *vdev, u64 iova, u64 length);
 	int	(*device_feature)(struct vfio_device *device, u32 flags,
 				  void __user *arg, size_t argsz);
 	struct file *(*migration_set_state)(
@@ -154,23 +158,6 @@ extern int vfio_unpin_pages(struct vfio_device *device, unsigned long *user_pfn,
 extern int vfio_dma_rw(struct vfio_device *device, dma_addr_t user_iova,
 		       void *data, size_t len, bool write);
 
-/* each type has independent events */
-enum vfio_notify_type {
-	VFIO_IOMMU_NOTIFY = 0,
-};
-
-/* events for VFIO_IOMMU_NOTIFY */
-#define VFIO_IOMMU_NOTIFY_DMA_UNMAP	BIT(0)
-
-extern int vfio_register_notifier(struct vfio_device *device,
-				  enum vfio_notify_type type,
-				  unsigned long *required_events,
-				  struct notifier_block *nb);
-extern int vfio_unregister_notifier(struct vfio_device *device,
-				    enum vfio_notify_type type,
-				    struct notifier_block *nb);
-
-
 /*
  * Sub-module helpers
  */
-- 
2.36.1

Re: [PATCH 1/2] vfio: Replace the DMA unmapping notifier with a callback

[Christoph Hellwig]

On Mon, Jun 06, 2022 at 09:34:35PM -0300, Jason Gunthorpe wrote:
> +static void intel_vgpu_dma_unmap(struct vfio_device *vfio_dev, u64 iova,
> +				 u64 length)
>  {
> +	struct intel_vgpu *vgpu = vfio_dev_to_vgpu(vfio_dev);
> +	struct gvt_dma *entry;
> +	u64 iov_pfn, end_iov_pfn;
>  
> +	iov_pfn = iova >> PAGE_SHIFT;
> +	end_iov_pfn = iov_pfn + length / PAGE_SIZE;

I'd just initialize these at declaration time.  The mix between
shifting and division here is also kind weird, but we probably
shouldn't change too much from the original version.

> +	/* Vendor drivers MUST unpin pages in response to an invalidation. */

s/Vendor//g

>  /**
> + * vfio_ap_mdev_dma_unmap - Notifier that IOVA has been unmapped
> + * @vdev: The VFIO device
> + * @unmap: IOVA range unmapped
>   *
> + * Unpin the guest IOVA (the NIB guest address we pinned before).
>   */

kerneldoc comments for method instances are a bit silly..

> +static int vfio_iommu_notifier(struct notifier_block *nb, unsigned long action,
> +			       void *data)
> +{
> +	struct vfio_device *vfio_device =
> +		container_of(nb, struct vfio_device, iommu_nb);
> +	struct vfio_iommu_type1_dma_unmap *unmap = data;

Using the iommu type 1 UAPI structure in the core vfio code for a
subset of its field is kinda weird.  But we can fix this later.

Otherwise looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [Intel-gfx] [PATCH 1/2] vfio: Replace the DMA unmapping notifier with a callback

[Christoph Hellwig]

On Mon, Jun 06, 2022 at 09:34:35PM -0300, Jason Gunthorpe wrote:
> +static void intel_vgpu_dma_unmap(struct vfio_device *vfio_dev, u64 iova,
> +				 u64 length)
>  {
> +	struct intel_vgpu *vgpu = vfio_dev_to_vgpu(vfio_dev);
> +	struct gvt_dma *entry;
> +	u64 iov_pfn, end_iov_pfn;
>  
> +	iov_pfn = iova >> PAGE_SHIFT;
> +	end_iov_pfn = iov_pfn + length / PAGE_SIZE;

I'd just initialize these at declaration time.  The mix between
shifting and division here is also kind weird, but we probably
shouldn't change too much from the original version.

> +	/* Vendor drivers MUST unpin pages in response to an invalidation. */

s/Vendor//g

>  /**
> + * vfio_ap_mdev_dma_unmap - Notifier that IOVA has been unmapped
> + * @vdev: The VFIO device
> + * @unmap: IOVA range unmapped
>   *
> + * Unpin the guest IOVA (the NIB guest address we pinned before).
>   */

kerneldoc comments for method instances are a bit silly..

> +static int vfio_iommu_notifier(struct notifier_block *nb, unsigned long action,
> +			       void *data)
> +{
> +	struct vfio_device *vfio_device =
> +		container_of(nb, struct vfio_device, iommu_nb);
> +	struct vfio_iommu_type1_dma_unmap *unmap = data;

Using the iommu type 1 UAPI structure in the core vfio code for a
subset of its field is kinda weird.  But we can fix this later.

Otherwise looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH 1/2] vfio: Replace the DMA unmapping notifier with a callback

[Jason Gunthorpe]

On Tue, Jun 07, 2022 at 07:39:55AM +0200, Christoph Hellwig wrote:

> > +static int vfio_iommu_notifier(struct notifier_block *nb, unsigned long action,
> > +			       void *data)
> > +{
> > +	struct vfio_device *vfio_device =
> > +		container_of(nb, struct vfio_device, iommu_nb);
> > +	struct vfio_iommu_type1_dma_unmap *unmap = data;
> 
> Using the iommu type 1 UAPI structure in the core vfio code for a
> subset of its field is kinda weird.  But we can fix this later.

Ah, I did type this in at one point.. It was small lets include it in
this patch

Thanks,
Jason

Re: [PATCH 1/2] vfio: Replace the DMA unmapping notifier with a callback

[Jason Gunthorpe]

On Tue, Jun 07, 2022 at 07:39:55AM +0200, Christoph Hellwig wrote:

> > +static int vfio_iommu_notifier(struct notifier_block *nb, unsigned long action,
> > +			       void *data)
> > +{
> > +	struct vfio_device *vfio_device =
> > +		container_of(nb, struct vfio_device, iommu_nb);
> > +	struct vfio_iommu_type1_dma_unmap *unmap = data;
> 
> Using the iommu type 1 UAPI structure in the core vfio code for a
> subset of its field is kinda weird.  But we can fix this later.

Ah, I did type this in at one point.. It was small lets include it in
this patch

Thanks,
Jason

Re: [Intel-gfx] [PATCH 1/2] vfio: Replace the DMA unmapping notifier with a callback

[Jason Gunthorpe]

On Tue, Jun 07, 2022 at 07:39:55AM +0200, Christoph Hellwig wrote:

> > +static int vfio_iommu_notifier(struct notifier_block *nb, unsigned long action,
> > +			       void *data)
> > +{
> > +	struct vfio_device *vfio_device =
> > +		container_of(nb, struct vfio_device, iommu_nb);
> > +	struct vfio_iommu_type1_dma_unmap *unmap = data;
> 
> Using the iommu type 1 UAPI structure in the core vfio code for a
> subset of its field is kinda weird.  But we can fix this later.

Ah, I did type this in at one point.. It was small lets include it in
this patch

Thanks,
Jason

Re: [PATCH 1/2] vfio: Replace the DMA unmapping notifier with a callback

[Jason Gunthorpe]

On Tue, Jun 07, 2022 at 08:57:52AM -0300, Jason Gunthorpe wrote:
> On Tue, Jun 07, 2022 at 07:39:55AM +0200, Christoph Hellwig wrote:
> 
> > > +static int vfio_iommu_notifier(struct notifier_block *nb, unsigned long action,
> > > +			       void *data)
> > > +{
> > > +	struct vfio_device *vfio_device =
> > > +		container_of(nb, struct vfio_device, iommu_nb);
> > > +	struct vfio_iommu_type1_dma_unmap *unmap = data;
> > 
> > Using the iommu type 1 UAPI structure in the core vfio code for a
> > subset of its field is kinda weird.  But we can fix this later.
> 
> Ah, I did type this in at one point.. It was small lets include it in
> this patch

Oh I got this explanation mixed up - forgot about this vesitgual bit

The patch is split in two: this patch removes the
vfio_iommu_type1_dma_unmap from all the drivers but leaves the type1
code as-is and bridges it here, the next patch changes the type1 code
to direcly call the op and deletes this function. So this weirdness is
fully deleted by the end of the series.

Jason

Re: [PATCH 1/2] vfio: Replace the DMA unmapping notifier with a callback

[Jason Gunthorpe]

On Tue, Jun 07, 2022 at 08:57:52AM -0300, Jason Gunthorpe wrote:
> On Tue, Jun 07, 2022 at 07:39:55AM +0200, Christoph Hellwig wrote:
> 
> > > +static int vfio_iommu_notifier(struct notifier_block *nb, unsigned long action,
> > > +			       void *data)
> > > +{
> > > +	struct vfio_device *vfio_device =
> > > +		container_of(nb, struct vfio_device, iommu_nb);
> > > +	struct vfio_iommu_type1_dma_unmap *unmap = data;
> > 
> > Using the iommu type 1 UAPI structure in the core vfio code for a
> > subset of its field is kinda weird.  But we can fix this later.
> 
> Ah, I did type this in at one point.. It was small lets include it in
> this patch

Oh I got this explanation mixed up - forgot about this vesitgual bit

The patch is split in two: this patch removes the
vfio_iommu_type1_dma_unmap from all the drivers but leaves the type1
code as-is and bridges it here, the next patch changes the type1 code
to direcly call the op and deletes this function. So this weirdness is
fully deleted by the end of the series.

Jason

Re: [Intel-gfx] [PATCH 1/2] vfio: Replace the DMA unmapping notifier with a callback

[Jason Gunthorpe]

On Tue, Jun 07, 2022 at 08:57:52AM -0300, Jason Gunthorpe wrote:
> On Tue, Jun 07, 2022 at 07:39:55AM +0200, Christoph Hellwig wrote:
> 
> > > +static int vfio_iommu_notifier(struct notifier_block *nb, unsigned long action,
> > > +			       void *data)
> > > +{
> > > +	struct vfio_device *vfio_device =
> > > +		container_of(nb, struct vfio_device, iommu_nb);
> > > +	struct vfio_iommu_type1_dma_unmap *unmap = data;
> > 
> > Using the iommu type 1 UAPI structure in the core vfio code for a
> > subset of its field is kinda weird.  But we can fix this later.
> 
> Ah, I did type this in at one point.. It was small lets include it in
> this patch

Oh I got this explanation mixed up - forgot about this vesitgual bit

The patch is split in two: this patch removes the
vfio_iommu_type1_dma_unmap from all the drivers but leaves the type1
code as-is and bridges it here, the next patch changes the type1 code
to direcly call the op and deletes this function. So this weirdness is
fully deleted by the end of the series.

Jason

[PATCH 2/2] vfio: Replace the iommu notifier with a device list

[Jason Gunthorpe]

Instead of bouncing the function call to the driver op through a blocking
notifier just have the iommu layer call it directly.

Register each device that is being attached to the iommu with the lower
driver which then threads them on a linked list and calls the appropriate
driver op at the right time.

Currently the only use is if dma_unmap() is defined.

Also, fully lock all the debugging tests on the pinning path that a
dma_unmap is registered.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
 drivers/vfio/vfio.c             | 39 ++++-------------
 drivers/vfio/vfio.h             | 14 ++-----
 drivers/vfio/vfio_iommu_type1.c | 74 ++++++++++++++++++++-------------
 include/linux/vfio.h            |  2 +-
 4 files changed, 58 insertions(+), 71 deletions(-)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index f005b644ab9e69..05623f52e38d32 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -1077,17 +1077,6 @@ static void vfio_device_unassign_container(struct vfio_device *device)
 	up_write(&device->group->group_rwsem);
 }
 
-static int vfio_iommu_notifier(struct notifier_block *nb, unsigned long action,
-			       void *data)
-{
-	struct vfio_device *vfio_device =
-		container_of(nb, struct vfio_device, iommu_nb);
-	struct vfio_iommu_type1_dma_unmap *unmap = data;
-
-	vfio_device->ops->dma_unmap(vfio_device, unmap->iova, unmap->size);
-	return NOTIFY_OK;
-}
-
 static struct file *vfio_device_open(struct vfio_device *device)
 {
 	struct vfio_iommu_driver *iommu_driver;
@@ -1123,15 +1112,9 @@ static struct file *vfio_device_open(struct vfio_device *device)
 		}
 
 		iommu_driver = device->group->container->iommu_driver;
-		if (device->ops->dma_unmap && iommu_driver &&
-		    iommu_driver->ops->register_notifier) {
-			unsigned long events = VFIO_IOMMU_NOTIFY_DMA_UNMAP;
-
-			device->iommu_nb.notifier_call = vfio_iommu_notifier;
-			iommu_driver->ops->register_notifier(
-				device->group->container->iommu_data, &events,
-				&device->iommu_nb);
-		}
+		if (iommu_driver && iommu_driver->ops->register_device)
+			iommu_driver->ops->register_device(
+				device->group->container->iommu_data, device);
 
 		up_read(&device->group->group_rwsem);
 	}
@@ -1171,11 +1154,9 @@ static struct file *vfio_device_open(struct vfio_device *device)
 		device->ops->close_device(device);
 
 		iommu_driver = device->group->container->iommu_driver;
-		if (device->ops->dma_unmap && iommu_driver &&
-		    iommu_driver->ops->register_notifier)
-			iommu_driver->ops->unregister_notifier(
-				device->group->container->iommu_data,
-				&device->iommu_nb);
+		if (iommu_driver && iommu_driver->ops->register_device)
+			iommu_driver->ops->unregister_device(
+				device->group->container->iommu_data, device);
 	}
 err_undo_count:
 	device->open_count--;
@@ -1380,11 +1361,9 @@ static int vfio_device_fops_release(struct inode *inode, struct file *filep)
 		device->ops->close_device(device);
 
 	iommu_driver = device->group->container->iommu_driver;
-	if (device->ops->dma_unmap && iommu_driver &&
-	    iommu_driver->ops->register_notifier)
-		iommu_driver->ops->unregister_notifier(
-			device->group->container->iommu_data,
-			&device->iommu_nb);
+	if (iommu_driver && iommu_driver->ops->unregister_device)
+		iommu_driver->ops->unregister_device(
+			device->group->container->iommu_data, device);
 	up_read(&device->group->group_rwsem);
 	device->open_count--;
 	if (device->open_count == 0)
diff --git a/drivers/vfio/vfio.h b/drivers/vfio/vfio.h
index cb2e4e9baa8fe8..4a7db1f3c33e7e 100644
--- a/drivers/vfio/vfio.h
+++ b/drivers/vfio/vfio.h
@@ -33,11 +33,6 @@ enum vfio_iommu_notify_type {
 	VFIO_IOMMU_CONTAINER_CLOSE = 0,
 };
 
-/* events for register_notifier() */
-enum {
-	VFIO_IOMMU_NOTIFY_DMA_UNMAP = 1,
-};
-
 /**
  * struct vfio_iommu_driver_ops - VFIO IOMMU driver callbacks
  */
@@ -60,11 +55,10 @@ struct vfio_iommu_driver_ops {
 				     unsigned long *phys_pfn);
 	int		(*unpin_pages)(void *iommu_data,
 				       unsigned long *user_pfn, int npage);
-	int		(*register_notifier)(void *iommu_data,
-					     unsigned long *events,
-					     struct notifier_block *nb);
-	int		(*unregister_notifier)(void *iommu_data,
-					       struct notifier_block *nb);
+	void		(*register_device)(void *iommu_data,
+					   struct vfio_device *vdev);
+	void		(*unregister_device)(void *iommu_data,
+					     struct vfio_device *vdev);
 	int		(*dma_rw)(void *iommu_data, dma_addr_t user_iova,
 				  void *data, size_t count, bool write);
 	struct iommu_domain *(*group_iommu_domain)(void *iommu_data,
diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index c13b9290e35759..7011fdeaf7db08 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -67,7 +67,8 @@ struct vfio_iommu {
 	struct list_head	iova_list;
 	struct mutex		lock;
 	struct rb_root		dma_list;
-	struct blocking_notifier_head notifier;
+	struct list_head	device_list;
+	struct mutex		device_list_lock;
 	unsigned int		dma_avail;
 	unsigned int		vaddr_invalid_count;
 	uint64_t		pgsize_bitmap;
@@ -865,8 +866,8 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
 		}
 	}
 
-	/* Fail if notifier list is empty */
-	if (!iommu->notifier.head) {
+	/* Fail if no dma_umap notifier is registered */
+	if (list_empty(&iommu->device_list)) {
 		ret = -EINVAL;
 		goto pin_done;
 	}
@@ -1406,7 +1407,7 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
 		}
 
 		if (!RB_EMPTY_ROOT(&dma->pfn_list)) {
-			struct vfio_iommu_type1_dma_unmap nb_unmap;
+			struct vfio_device *device;
 
 			if (dma_last == dma) {
 				BUG_ON(++retries > 10);
@@ -1415,20 +1416,25 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
 				retries = 0;
 			}
 
-			nb_unmap.iova = dma->iova;
-			nb_unmap.size = dma->size;
-
 			/*
 			 * Notify anyone (mdev vendor drivers) to invalidate and
 			 * unmap iovas within the range we're about to unmap.
 			 * Vendor drivers MUST unpin pages in response to an
 			 * invalidation.
 			 */
-			mutex_unlock(&iommu->lock);
-			blocking_notifier_call_chain(&iommu->notifier,
-						    VFIO_IOMMU_NOTIFY_DMA_UNMAP,
-						    &nb_unmap);
-			mutex_lock(&iommu->lock);
+			if (!list_empty(&iommu->device_list)) {
+				mutex_lock(&iommu->device_list_lock);
+				mutex_unlock(&iommu->lock);
+
+				list_for_each_entry(device,
+						    &iommu->device_list,
+						    iommu_entry)
+					device->ops->dma_unmap(
+						device, dma->iova, dma->size);
+
+				mutex_unlock(&iommu->device_list_lock);
+				mutex_lock(&iommu->lock);
+			}
 			goto again;
 		}
 
@@ -2478,7 +2484,7 @@ static void vfio_iommu_type1_detach_group(void *iommu_data,
 
 		if (list_empty(&iommu->emulated_iommu_groups) &&
 		    list_empty(&iommu->domain_list)) {
-			WARN_ON(iommu->notifier.head);
+			WARN_ON(!list_empty(&iommu->device_list));
 			vfio_iommu_unmap_unpin_all(iommu);
 		}
 		goto detach_group_done;
@@ -2510,7 +2516,8 @@ static void vfio_iommu_type1_detach_group(void *iommu_data,
 		if (list_empty(&domain->group_list)) {
 			if (list_is_singular(&iommu->domain_list)) {
 				if (list_empty(&iommu->emulated_iommu_groups)) {
-					WARN_ON(iommu->notifier.head);
+					WARN_ON(!list_empty(
+						&iommu->device_list));
 					vfio_iommu_unmap_unpin_all(iommu);
 				} else {
 					vfio_iommu_unmap_unpin_reaccount(iommu);
@@ -2571,7 +2578,8 @@ static void *vfio_iommu_type1_open(unsigned long arg)
 	iommu->dma_avail = dma_entry_limit;
 	iommu->container_open = true;
 	mutex_init(&iommu->lock);
-	BLOCKING_INIT_NOTIFIER_HEAD(&iommu->notifier);
+	mutex_init(&iommu->device_list_lock);
+	INIT_LIST_HEAD(&iommu->device_list);
 	init_waitqueue_head(&iommu->vaddr_wait);
 	iommu->pgsize_bitmap = PAGE_MASK;
 	INIT_LIST_HEAD(&iommu->emulated_iommu_groups);
@@ -3008,28 +3016,34 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
 	}
 }
 
-static int vfio_iommu_type1_register_notifier(void *iommu_data,
-					      unsigned long *events,
-					      struct notifier_block *nb)
+static void vfio_iommu_type1_register_device(void *iommu_data,
+					     struct vfio_device *vdev)
 {
 	struct vfio_iommu *iommu = iommu_data;
 
-	/* clear known events */
-	*events &= ~VFIO_IOMMU_NOTIFY_DMA_UNMAP;
-
-	/* refuse to register if still events remaining */
-	if (*events)
-		return -EINVAL;
+	if (!vdev->ops->dma_unmap)
+		return;
 
-	return blocking_notifier_chain_register(&iommu->notifier, nb);
+	mutex_lock(&iommu->lock);
+	mutex_lock(&iommu->device_list_lock);
+	list_add(&vdev->iommu_entry, &iommu->device_list);
+	mutex_unlock(&iommu->device_list_lock);
+	mutex_unlock(&iommu->lock);
 }
 
-static int vfio_iommu_type1_unregister_notifier(void *iommu_data,
-						struct notifier_block *nb)
+static void vfio_iommu_type1_unregister_device(void *iommu_data,
+					       struct vfio_device *vdev)
 {
 	struct vfio_iommu *iommu = iommu_data;
 
-	return blocking_notifier_chain_unregister(&iommu->notifier, nb);
+	if (!vdev->ops->dma_unmap)
+		return;
+
+	mutex_lock(&iommu->lock);
+	mutex_lock(&iommu->device_list_lock);
+	list_del(&vdev->iommu_entry);
+	mutex_unlock(&iommu->device_list_lock);
+	mutex_unlock(&iommu->lock);
 }
 
 static int vfio_iommu_type1_dma_rw_chunk(struct vfio_iommu *iommu,
@@ -3163,8 +3177,8 @@ static const struct vfio_iommu_driver_ops vfio_iommu_driver_ops_type1 = {
 	.detach_group		= vfio_iommu_type1_detach_group,
 	.pin_pages		= vfio_iommu_type1_pin_pages,
 	.unpin_pages		= vfio_iommu_type1_unpin_pages,
-	.register_notifier	= vfio_iommu_type1_register_notifier,
-	.unregister_notifier	= vfio_iommu_type1_unregister_notifier,
+	.register_device	= vfio_iommu_type1_register_device,
+	.unregister_device	= vfio_iommu_type1_unregister_device,
 	.dma_rw			= vfio_iommu_type1_dma_rw,
 	.group_iommu_domain	= vfio_iommu_type1_group_iommu_domain,
 	.notify			= vfio_iommu_type1_notify,
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index b76623e3b92fca..c22d3f1e13b66c 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -44,7 +44,7 @@ struct vfio_device {
 	unsigned int open_count;
 	struct completion comp;
 	struct list_head group_next;
-	struct notifier_block iommu_nb;
+	struct list_head iommu_entry;
 };
 
 /**
-- 
2.36.1

[Intel-gfx] [PATCH 2/2] vfio: Replace the iommu notifier with a device list

[Jason Gunthorpe]

Instead of bouncing the function call to the driver op through a blocking
notifier just have the iommu layer call it directly.

Register each device that is being attached to the iommu with the lower
driver which then threads them on a linked list and calls the appropriate
driver op at the right time.

Currently the only use is if dma_unmap() is defined.

Also, fully lock all the debugging tests on the pinning path that a
dma_unmap is registered.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
 drivers/vfio/vfio.c             | 39 ++++-------------
 drivers/vfio/vfio.h             | 14 ++-----
 drivers/vfio/vfio_iommu_type1.c | 74 ++++++++++++++++++++-------------
 include/linux/vfio.h            |  2 +-
 4 files changed, 58 insertions(+), 71 deletions(-)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index f005b644ab9e69..05623f52e38d32 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -1077,17 +1077,6 @@ static void vfio_device_unassign_container(struct vfio_device *device)
 	up_write(&device->group->group_rwsem);
 }
 
-static int vfio_iommu_notifier(struct notifier_block *nb, unsigned long action,
-			       void *data)
-{
-	struct vfio_device *vfio_device =
-		container_of(nb, struct vfio_device, iommu_nb);
-	struct vfio_iommu_type1_dma_unmap *unmap = data;
-
-	vfio_device->ops->dma_unmap(vfio_device, unmap->iova, unmap->size);
-	return NOTIFY_OK;
-}
-
 static struct file *vfio_device_open(struct vfio_device *device)
 {
 	struct vfio_iommu_driver *iommu_driver;
@@ -1123,15 +1112,9 @@ static struct file *vfio_device_open(struct vfio_device *device)
 		}
 
 		iommu_driver = device->group->container->iommu_driver;
-		if (device->ops->dma_unmap && iommu_driver &&
-		    iommu_driver->ops->register_notifier) {
-			unsigned long events = VFIO_IOMMU_NOTIFY_DMA_UNMAP;
-
-			device->iommu_nb.notifier_call = vfio_iommu_notifier;
-			iommu_driver->ops->register_notifier(
-				device->group->container->iommu_data, &events,
-				&device->iommu_nb);
-		}
+		if (iommu_driver && iommu_driver->ops->register_device)
+			iommu_driver->ops->register_device(
+				device->group->container->iommu_data, device);
 
 		up_read(&device->group->group_rwsem);
 	}
@@ -1171,11 +1154,9 @@ static struct file *vfio_device_open(struct vfio_device *device)
 		device->ops->close_device(device);
 
 		iommu_driver = device->group->container->iommu_driver;
-		if (device->ops->dma_unmap && iommu_driver &&
-		    iommu_driver->ops->register_notifier)
-			iommu_driver->ops->unregister_notifier(
-				device->group->container->iommu_data,
-				&device->iommu_nb);
+		if (iommu_driver && iommu_driver->ops->register_device)
+			iommu_driver->ops->unregister_device(
+				device->group->container->iommu_data, device);
 	}
 err_undo_count:
 	device->open_count--;
@@ -1380,11 +1361,9 @@ static int vfio_device_fops_release(struct inode *inode, struct file *filep)
 		device->ops->close_device(device);
 
 	iommu_driver = device->group->container->iommu_driver;
-	if (device->ops->dma_unmap && iommu_driver &&
-	    iommu_driver->ops->register_notifier)
-		iommu_driver->ops->unregister_notifier(
-			device->group->container->iommu_data,
-			&device->iommu_nb);
+	if (iommu_driver && iommu_driver->ops->unregister_device)
+		iommu_driver->ops->unregister_device(
+			device->group->container->iommu_data, device);
 	up_read(&device->group->group_rwsem);
 	device->open_count--;
 	if (device->open_count == 0)
diff --git a/drivers/vfio/vfio.h b/drivers/vfio/vfio.h
index cb2e4e9baa8fe8..4a7db1f3c33e7e 100644
--- a/drivers/vfio/vfio.h
+++ b/drivers/vfio/vfio.h
@@ -33,11 +33,6 @@ enum vfio_iommu_notify_type {
 	VFIO_IOMMU_CONTAINER_CLOSE = 0,
 };
 
-/* events for register_notifier() */
-enum {
-	VFIO_IOMMU_NOTIFY_DMA_UNMAP = 1,
-};
-
 /**
  * struct vfio_iommu_driver_ops - VFIO IOMMU driver callbacks
  */
@@ -60,11 +55,10 @@ struct vfio_iommu_driver_ops {
 				     unsigned long *phys_pfn);
 	int		(*unpin_pages)(void *iommu_data,
 				       unsigned long *user_pfn, int npage);
-	int		(*register_notifier)(void *iommu_data,
-					     unsigned long *events,
-					     struct notifier_block *nb);
-	int		(*unregister_notifier)(void *iommu_data,
-					       struct notifier_block *nb);
+	void		(*register_device)(void *iommu_data,
+					   struct vfio_device *vdev);
+	void		(*unregister_device)(void *iommu_data,
+					     struct vfio_device *vdev);
 	int		(*dma_rw)(void *iommu_data, dma_addr_t user_iova,
 				  void *data, size_t count, bool write);
 	struct iommu_domain *(*group_iommu_domain)(void *iommu_data,
diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index c13b9290e35759..7011fdeaf7db08 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -67,7 +67,8 @@ struct vfio_iommu {
 	struct list_head	iova_list;
 	struct mutex		lock;
 	struct rb_root		dma_list;
-	struct blocking_notifier_head notifier;
+	struct list_head	device_list;
+	struct mutex		device_list_lock;
 	unsigned int		dma_avail;
 	unsigned int		vaddr_invalid_count;
 	uint64_t		pgsize_bitmap;
@@ -865,8 +866,8 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
 		}
 	}
 
-	/* Fail if notifier list is empty */
-	if (!iommu->notifier.head) {
+	/* Fail if no dma_umap notifier is registered */
+	if (list_empty(&iommu->device_list)) {
 		ret = -EINVAL;
 		goto pin_done;
 	}
@@ -1406,7 +1407,7 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
 		}
 
 		if (!RB_EMPTY_ROOT(&dma->pfn_list)) {
-			struct vfio_iommu_type1_dma_unmap nb_unmap;
+			struct vfio_device *device;
 
 			if (dma_last == dma) {
 				BUG_ON(++retries > 10);
@@ -1415,20 +1416,25 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
 				retries = 0;
 			}
 
-			nb_unmap.iova = dma->iova;
-			nb_unmap.size = dma->size;
-
 			/*
 			 * Notify anyone (mdev vendor drivers) to invalidate and
 			 * unmap iovas within the range we're about to unmap.
 			 * Vendor drivers MUST unpin pages in response to an
 			 * invalidation.
 			 */
-			mutex_unlock(&iommu->lock);
-			blocking_notifier_call_chain(&iommu->notifier,
-						    VFIO_IOMMU_NOTIFY_DMA_UNMAP,
-						    &nb_unmap);
-			mutex_lock(&iommu->lock);
+			if (!list_empty(&iommu->device_list)) {
+				mutex_lock(&iommu->device_list_lock);
+				mutex_unlock(&iommu->lock);
+
+				list_for_each_entry(device,
+						    &iommu->device_list,
+						    iommu_entry)
+					device->ops->dma_unmap(
+						device, dma->iova, dma->size);
+
+				mutex_unlock(&iommu->device_list_lock);
+				mutex_lock(&iommu->lock);
+			}
 			goto again;
 		}
 
@@ -2478,7 +2484,7 @@ static void vfio_iommu_type1_detach_group(void *iommu_data,
 
 		if (list_empty(&iommu->emulated_iommu_groups) &&
 		    list_empty(&iommu->domain_list)) {
-			WARN_ON(iommu->notifier.head);
+			WARN_ON(!list_empty(&iommu->device_list));
 			vfio_iommu_unmap_unpin_all(iommu);
 		}
 		goto detach_group_done;
@@ -2510,7 +2516,8 @@ static void vfio_iommu_type1_detach_group(void *iommu_data,
 		if (list_empty(&domain->group_list)) {
 			if (list_is_singular(&iommu->domain_list)) {
 				if (list_empty(&iommu->emulated_iommu_groups)) {
-					WARN_ON(iommu->notifier.head);
+					WARN_ON(!list_empty(
+						&iommu->device_list));
 					vfio_iommu_unmap_unpin_all(iommu);
 				} else {
 					vfio_iommu_unmap_unpin_reaccount(iommu);
@@ -2571,7 +2578,8 @@ static void *vfio_iommu_type1_open(unsigned long arg)
 	iommu->dma_avail = dma_entry_limit;
 	iommu->container_open = true;
 	mutex_init(&iommu->lock);
-	BLOCKING_INIT_NOTIFIER_HEAD(&iommu->notifier);
+	mutex_init(&iommu->device_list_lock);
+	INIT_LIST_HEAD(&iommu->device_list);
 	init_waitqueue_head(&iommu->vaddr_wait);
 	iommu->pgsize_bitmap = PAGE_MASK;
 	INIT_LIST_HEAD(&iommu->emulated_iommu_groups);
@@ -3008,28 +3016,34 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
 	}
 }
 
-static int vfio_iommu_type1_register_notifier(void *iommu_data,
-					      unsigned long *events,
-					      struct notifier_block *nb)
+static void vfio_iommu_type1_register_device(void *iommu_data,
+					     struct vfio_device *vdev)
 {
 	struct vfio_iommu *iommu = iommu_data;
 
-	/* clear known events */
-	*events &= ~VFIO_IOMMU_NOTIFY_DMA_UNMAP;
-
-	/* refuse to register if still events remaining */
-	if (*events)
-		return -EINVAL;
+	if (!vdev->ops->dma_unmap)
+		return;
 
-	return blocking_notifier_chain_register(&iommu->notifier, nb);
+	mutex_lock(&iommu->lock);
+	mutex_lock(&iommu->device_list_lock);
+	list_add(&vdev->iommu_entry, &iommu->device_list);
+	mutex_unlock(&iommu->device_list_lock);
+	mutex_unlock(&iommu->lock);
 }
 
-static int vfio_iommu_type1_unregister_notifier(void *iommu_data,
-						struct notifier_block *nb)
+static void vfio_iommu_type1_unregister_device(void *iommu_data,
+					       struct vfio_device *vdev)
 {
 	struct vfio_iommu *iommu = iommu_data;
 
-	return blocking_notifier_chain_unregister(&iommu->notifier, nb);
+	if (!vdev->ops->dma_unmap)
+		return;
+
+	mutex_lock(&iommu->lock);
+	mutex_lock(&iommu->device_list_lock);
+	list_del(&vdev->iommu_entry);
+	mutex_unlock(&iommu->device_list_lock);
+	mutex_unlock(&iommu->lock);
 }
 
 static int vfio_iommu_type1_dma_rw_chunk(struct vfio_iommu *iommu,
@@ -3163,8 +3177,8 @@ static const struct vfio_iommu_driver_ops vfio_iommu_driver_ops_type1 = {
 	.detach_group		= vfio_iommu_type1_detach_group,
 	.pin_pages		= vfio_iommu_type1_pin_pages,
 	.unpin_pages		= vfio_iommu_type1_unpin_pages,
-	.register_notifier	= vfio_iommu_type1_register_notifier,
-	.unregister_notifier	= vfio_iommu_type1_unregister_notifier,
+	.register_device	= vfio_iommu_type1_register_device,
+	.unregister_device	= vfio_iommu_type1_unregister_device,
 	.dma_rw			= vfio_iommu_type1_dma_rw,
 	.group_iommu_domain	= vfio_iommu_type1_group_iommu_domain,
 	.notify			= vfio_iommu_type1_notify,
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index b76623e3b92fca..c22d3f1e13b66c 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -44,7 +44,7 @@ struct vfio_device {
 	unsigned int open_count;
 	struct completion comp;
 	struct list_head group_next;
-	struct notifier_block iommu_nb;
+	struct list_head iommu_entry;
 };
 
 /**
-- 
2.36.1

Re: [PATCH 2/2] vfio: Replace the iommu notifier with a device list

[Christoph Hellwig]

On Mon, Jun 06, 2022 at 09:34:36PM -0300, Jason Gunthorpe wrote:
> +			if (!list_empty(&iommu->device_list)) {
> +				mutex_lock(&iommu->device_list_lock);
> +				mutex_unlock(&iommu->lock);
> +
> +				list_for_each_entry(device,
> +						    &iommu->device_list,
> +						    iommu_entry)
> +					device->ops->dma_unmap(
> +						device, dma->iova, dma->size);
> +
> +				mutex_unlock(&iommu->device_list_lock);
> +				mutex_lock(&iommu->lock);
> +			}

I wonder if factoring this into a little helper instead of the
very deep indentation might be a bit better for readability.

> +static void vfio_iommu_type1_register_device(void *iommu_data,
> +					     struct vfio_device *vdev)
>  {
>  	struct vfio_iommu *iommu = iommu_data;
>  
> +	if (!vdev->ops->dma_unmap)
> +		return;
>  
> +	mutex_lock(&iommu->lock);
> +	mutex_lock(&iommu->device_list_lock);
> +	list_add(&vdev->iommu_entry, &iommu->device_list);
> +	mutex_unlock(&iommu->device_list_lock);
> +	mutex_unlock(&iommu->lock);

Why do we need both iommu->lock and the device_list_lock everywhere?
Maybe explain the locking scheme somewhere so that people don't have
to guess, because it seems to me that just using iommu->lock would
be enough right now.

Re: [Intel-gfx] [PATCH 2/2] vfio: Replace the iommu notifier with a device list

[Christoph Hellwig]

On Mon, Jun 06, 2022 at 09:34:36PM -0300, Jason Gunthorpe wrote:
> +			if (!list_empty(&iommu->device_list)) {
> +				mutex_lock(&iommu->device_list_lock);
> +				mutex_unlock(&iommu->lock);
> +
> +				list_for_each_entry(device,
> +						    &iommu->device_list,
> +						    iommu_entry)
> +					device->ops->dma_unmap(
> +						device, dma->iova, dma->size);
> +
> +				mutex_unlock(&iommu->device_list_lock);
> +				mutex_lock(&iommu->lock);
> +			}

I wonder if factoring this into a little helper instead of the
very deep indentation might be a bit better for readability.

> +static void vfio_iommu_type1_register_device(void *iommu_data,
> +					     struct vfio_device *vdev)
>  {
>  	struct vfio_iommu *iommu = iommu_data;
>  
> +	if (!vdev->ops->dma_unmap)
> +		return;
>  
> +	mutex_lock(&iommu->lock);
> +	mutex_lock(&iommu->device_list_lock);
> +	list_add(&vdev->iommu_entry, &iommu->device_list);
> +	mutex_unlock(&iommu->device_list_lock);
> +	mutex_unlock(&iommu->lock);

Why do we need both iommu->lock and the device_list_lock everywhere?
Maybe explain the locking scheme somewhere so that people don't have
to guess, because it seems to me that just using iommu->lock would
be enough right now.

Re: [PATCH 2/2] vfio: Replace the iommu notifier with a device list

[Jason Gunthorpe]

On Tue, Jun 07, 2022 at 07:44:37AM +0200, Christoph Hellwig wrote:
> On Mon, Jun 06, 2022 at 09:34:36PM -0300, Jason Gunthorpe wrote:
> > +			if (!list_empty(&iommu->device_list)) {
> > +				mutex_lock(&iommu->device_list_lock);
> > +				mutex_unlock(&iommu->lock);
> > +
> > +				list_for_each_entry(device,
> > +						    &iommu->device_list,
> > +						    iommu_entry)
> > +					device->ops->dma_unmap(
> > +						device, dma->iova, dma->size);
> > +
> > +				mutex_unlock(&iommu->device_list_lock);
> > +				mutex_lock(&iommu->lock);
> > +			}
> 
> I wonder if factoring this into a little helper instead of the
> very deep indentation might be a bit better for readability.
> 
> > +static void vfio_iommu_type1_register_device(void *iommu_data,
> > +					     struct vfio_device *vdev)
> >  {
> >  	struct vfio_iommu *iommu = iommu_data;
> >  
> > +	if (!vdev->ops->dma_unmap)
> > +		return;
> >  
> > +	mutex_lock(&iommu->lock);
> > +	mutex_lock(&iommu->device_list_lock);
> > +	list_add(&vdev->iommu_entry, &iommu->device_list);
> > +	mutex_unlock(&iommu->device_list_lock);
> > +	mutex_unlock(&iommu->lock);
> 
> Why do we need both iommu->lock and the device_list_lock everywhere?

Not everwhere, all the readers are using only one of the locks.  The
list empty calls that were previously unlocked are done under the
iommu->lock and only the list iteration was done under the
device_list.

> Maybe explain the locking scheme somewhere so that people don't have
> to guess, because it seems to me that just using iommu->lock would
> be enough right now.

The expectation is that the dma_umap callback will re-enter the type1
driver via vfio_unpin_pages calls and this will recurse back onto the
iommu->lock - so it must be dropped before invoking the callback.

I'll add a note

Jason

Re: [Intel-gfx] [PATCH 2/2] vfio: Replace the iommu notifier with a device list

[Jason Gunthorpe]

On Tue, Jun 07, 2022 at 07:44:37AM +0200, Christoph Hellwig wrote:
> On Mon, Jun 06, 2022 at 09:34:36PM -0300, Jason Gunthorpe wrote:
> > +			if (!list_empty(&iommu->device_list)) {
> > +				mutex_lock(&iommu->device_list_lock);
> > +				mutex_unlock(&iommu->lock);
> > +
> > +				list_for_each_entry(device,
> > +						    &iommu->device_list,
> > +						    iommu_entry)
> > +					device->ops->dma_unmap(
> > +						device, dma->iova, dma->size);
> > +
> > +				mutex_unlock(&iommu->device_list_lock);
> > +				mutex_lock(&iommu->lock);
> > +			}
> 
> I wonder if factoring this into a little helper instead of the
> very deep indentation might be a bit better for readability.
> 
> > +static void vfio_iommu_type1_register_device(void *iommu_data,
> > +					     struct vfio_device *vdev)
> >  {
> >  	struct vfio_iommu *iommu = iommu_data;
> >  
> > +	if (!vdev->ops->dma_unmap)
> > +		return;
> >  
> > +	mutex_lock(&iommu->lock);
> > +	mutex_lock(&iommu->device_list_lock);
> > +	list_add(&vdev->iommu_entry, &iommu->device_list);
> > +	mutex_unlock(&iommu->device_list_lock);
> > +	mutex_unlock(&iommu->lock);
> 
> Why do we need both iommu->lock and the device_list_lock everywhere?

Not everwhere, all the readers are using only one of the locks.  The
list empty calls that were previously unlocked are done under the
iommu->lock and only the list iteration was done under the
device_list.

> Maybe explain the locking scheme somewhere so that people don't have
> to guess, because it seems to me that just using iommu->lock would
> be enough right now.

The expectation is that the dma_umap callback will re-enter the type1
driver via vfio_unpin_pages calls and this will recurse back onto the
iommu->lock - so it must be dropped before invoking the callback.

I'll add a note

Jason

Re: [PATCH 2/2] vfio: Replace the iommu notifier with a device list

[Jason Gunthorpe]

On Tue, Jun 07, 2022 at 07:44:37AM +0200, Christoph Hellwig wrote:
> On Mon, Jun 06, 2022 at 09:34:36PM -0300, Jason Gunthorpe wrote:
> > +			if (!list_empty(&iommu->device_list)) {
> > +				mutex_lock(&iommu->device_list_lock);
> > +				mutex_unlock(&iommu->lock);
> > +
> > +				list_for_each_entry(device,
> > +						    &iommu->device_list,
> > +						    iommu_entry)
> > +					device->ops->dma_unmap(
> > +						device, dma->iova, dma->size);
> > +
> > +				mutex_unlock(&iommu->device_list_lock);
> > +				mutex_lock(&iommu->lock);
> > +			}
> 
> I wonder if factoring this into a little helper instead of the
> very deep indentation might be a bit better for readability.
> 
> > +static void vfio_iommu_type1_register_device(void *iommu_data,
> > +					     struct vfio_device *vdev)
> >  {
> >  	struct vfio_iommu *iommu = iommu_data;
> >  
> > +	if (!vdev->ops->dma_unmap)
> > +		return;
> >  
> > +	mutex_lock(&iommu->lock);
> > +	mutex_lock(&iommu->device_list_lock);
> > +	list_add(&vdev->iommu_entry, &iommu->device_list);
> > +	mutex_unlock(&iommu->device_list_lock);
> > +	mutex_unlock(&iommu->lock);
> 
> Why do we need both iommu->lock and the device_list_lock everywhere?

Not everwhere, all the readers are using only one of the locks.  The
list empty calls that were previously unlocked are done under the
iommu->lock and only the list iteration was done under the
device_list.

> Maybe explain the locking scheme somewhere so that people don't have
> to guess, because it seems to me that just using iommu->lock would
> be enough right now.

The expectation is that the dma_umap callback will re-enter the type1
driver via vfio_unpin_pages calls and this will recurse back onto the
iommu->lock - so it must be dropped before invoking the callback.

I'll add a note

Jason

[Intel-gfx] ✗ Fi.CI.BUILD: failure for Remove the VFIO_IOMMU_NOTIFY_DMA_UNMAP notifier

[Patchwork]

== Series Details ==

Series: Remove the VFIO_IOMMU_NOTIFY_DMA_UNMAP notifier
URL   : https://patchwork.freedesktop.org/series/104793/
State : failure

== Summary ==

Error: patch https://patchwork.freedesktop.org/api/1.0/series/104793/revisions/1/mbox/ not applied
Applying: vfio: Replace the DMA unmapping notifier with a callback
Using index info to reconstruct a base tree...
M	drivers/gpu/drm/i915/gvt/gvt.h
M	drivers/gpu/drm/i915/gvt/kvmgt.c
M	drivers/s390/cio/vfio_ccw_ops.c
M	drivers/s390/crypto/vfio_ap_ops.c
M	drivers/s390/crypto/vfio_ap_private.h
M	drivers/vfio/vfio.c
M	include/linux/vfio.h
Falling back to patching base and 3-way merge...
Auto-merging include/linux/vfio.h
CONFLICT (content): Merge conflict in include/linux/vfio.h
Auto-merging drivers/vfio/vfio.c
CONFLICT (content): Merge conflict in drivers/vfio/vfio.c
Auto-merging drivers/s390/crypto/vfio_ap_private.h
CONFLICT (content): Merge conflict in drivers/s390/crypto/vfio_ap_private.h
Auto-merging drivers/s390/crypto/vfio_ap_ops.c
CONFLICT (content): Merge conflict in drivers/s390/crypto/vfio_ap_ops.c
Auto-merging drivers/s390/cio/vfio_ccw_ops.c
CONFLICT (content): Merge conflict in drivers/s390/cio/vfio_ccw_ops.c
Auto-merging drivers/gpu/drm/i915/gvt/kvmgt.c
CONFLICT (content): Merge conflict in drivers/gpu/drm/i915/gvt/kvmgt.c
Auto-merging drivers/gpu/drm/i915/gvt/gvt.h
CONFLICT (content): Merge conflict in drivers/gpu/drm/i915/gvt/gvt.h
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
Patch failed at 0001 vfio: Replace the DMA unmapping notifier with a callback
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".