[05/14] vfio: refactor noiommu group creation

Commit Message

Christoph Hellwig Aug. 24, 2021, 2:46 p.m. UTC

Split the actual noiommu group creation from vfio_iommu_group_get into a
new helper, and open code the rest of vfio_iommu_group_get in its only
caller.  This creates an antirely separate and clear code path for the
noiommu group creation.

Signed-off-by: Christoph Hellwig <[e-mail]>
---
 drivers/vfio/vfio.c | 100 +++++++++++++++++++++++---------------------
 1 file changed, 53 insertions(+), 47 deletions(-)

Comments

Jason Gunthorpe Aug. 24, 2021, 11:43 p.m. UTC | #1

On Tue, Aug 24, 2021 at 04:46:40PM +0200, Christoph Hellwig wrote:
> Split the actual noiommu group creation from vfio_iommu_group_get into a
> new helper, and open code the rest of vfio_iommu_group_get in its only
> caller.  This creates an antirely separate and clear code path for the
> noiommu group creation.
> 
> Signed-off-by: Christoph Hellwig <[e-mail]>
> ---
>  drivers/vfio/vfio.c | 100 +++++++++++++++++++++++---------------------
>  1 file changed, 53 insertions(+), 47 deletions(-)

Reviewed-by: Jason Gunthorpe <[e-mail]>

Jason

Patch

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 9e97ad36a1c052..53e0d52f3b0209 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -169,50 +169,6 @@  static void vfio_release_device_set(struct vfio_device *device)
 	xa_unlock(&vfio_device_set_xa);
 }
 
-static struct iommu_group *vfio_iommu_group_get(struct device *dev)
-{
-	struct iommu_group *group;
-	int __maybe_unused ret;
-
-	group = iommu_group_get(dev);
-
-#ifdef CONFIG_VFIO_NOIOMMU
-	/*
-	 * With noiommu enabled, an IOMMU group will be created for a device
-	 * that doesn't already have one and doesn't have an iommu_ops on their
-	 * bus.  We set iommudata simply to be able to identify these groups
-	 * as special use and for reclamation later.
-	 */
-	if (group || !noiommu || iommu_present(dev->bus))
-		return group;
-
-	group = iommu_group_alloc();
-	if (IS_ERR(group))
-		return NULL;
-
-	iommu_group_set_name(group, "vfio-noiommu");
-	iommu_group_set_iommudata(group, &noiommu, NULL);
-	ret = iommu_group_add_device(group, dev);
-	if (ret) {
-		iommu_group_put(group);
-		return NULL;
-	}
-
-	/*
-	 * Where to taint?  At this point we've added an IOMMU group for a
-	 * device that is not backed by iommu_ops, therefore any iommu_
-	 * callback using iommu_ops can legitimately Oops.  So, while we may
-	 * be about to give a DMA capable device to a user without IOMMU
-	 * protection, which is clearly taint-worthy, let's go ahead and do
-	 * it here.
-	 */
-	add_taint(TAINT_USER, LOCKDEP_STILL_OK);
-	dev_warn(dev, "Adding kernel taint for vfio-noiommu group on device\n");
-#endif
-
-	return group;
-}
-
 static void vfio_iommu_group_put(struct iommu_group *group, struct device *dev)
 {
 #ifdef CONFIG_VFIO_NOIOMMU
@@ -833,12 +789,61 @@  void vfio_uninit_group_dev(struct vfio_device *device)
 }
 EXPORT_SYMBOL_GPL(vfio_uninit_group_dev);
 
-struct vfio_group *vfio_group_find_or_alloc(struct device *dev)
+#ifdef CONFIG_VFIO_NOIOMMU
+static struct vfio_group *vfio_noiommu_group_alloc(struct device *dev)
 {
 	struct iommu_group *iommu_group;
 	struct vfio_group *group;
+	int ret;
+
+	iommu_group = iommu_group_alloc();
+	if (IS_ERR(iommu_group))
+		return ERR_CAST(iommu_group);
 
-	iommu_group = vfio_iommu_group_get(dev);
+	iommu_group_set_name(iommu_group, "vfio-noiommu");
+	iommu_group_set_iommudata(iommu_group, &noiommu, NULL);
+	ret = iommu_group_add_device(iommu_group, dev);
+	if (ret)
+		goto out_put_group;
+
+	group = vfio_create_group(iommu_group);
+	if (IS_ERR(group)) {
+		ret = PTR_ERR(group);
+		goto out_remove_device;
+	}
+
+	return group;
+
+out_remove_device:
+	iommu_group_remove_device(dev);
+out_put_group:
+	iommu_group_put(iommu_group);
+	return ERR_PTR(ret);
+}
+#endif
+
+static struct vfio_group *vfio_group_find_or_alloc(struct device *dev)
+{
+	struct iommu_group *iommu_group;
+	struct vfio_group *group;
+
+	iommu_group = iommu_group_get(dev);
+#ifdef CONFIG_VFIO_NOIOMMU
+	if (!iommu_group && noiommu && !iommu_present(dev->bus)) {
+		/*
+		 * With noiommu enabled, create an IOMMU group for devices that
+		 * don't already have one and don't have an iommu_ops on their
+		 * bus.  Taint the kernel because we're about to give a DMA
+		 * capable device to a user without IOMMU protection.
+		 */
+		group = vfio_noiommu_group_alloc(dev);
+		if (group) {
+			add_taint(TAINT_USER, LOCKDEP_STILL_OK);
+			dev_warn(dev, "Adding kernel taint for vfio-noiommu group on device\n");
+		}
+		return group;
+	}
+#endif
 	if (!iommu_group)
 		return ERR_PTR(-EINVAL);
 
@@ -852,7 +857,8 @@  struct vfio_group *vfio_group_find_or_alloc(struct device *dev)
 		if (!IS_ERR(group))
 			return group;
 	}
-	vfio_iommu_group_put(iommu_group, dev);
+
+	iommu_group_put(iommu_group);
 	return group;
 }