[PATCH RFC 2/3] vfio: report group noiommu status

[Michael S. Tsirkin]

When using vfio, callers might want to know whether device is added to a
regular group or an non-iommu group.

Report this status from vfio_add_group_dev.

Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
---
 drivers/vfio/pci/vfio_pci.c                  | 2 +-
 drivers/vfio/platform/vfio_platform_common.c | 2 +-
 drivers/vfio/vfio.c                          | 5 ++++-
 Documentation/vfio.txt                       | 4 +++-
 4 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 712a849..d622a41 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -1119,7 +1119,7 @@ static int vfio_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	spin_lock_init(&vdev->irqlock);
 
 	ret = vfio_add_group_dev(&pdev->dev, &vfio_pci_ops, vdev);
-	if (ret) {
+	if (ret < 0) {
 		vfio_iommu_group_put(group, &pdev->dev);
 		kfree(vdev);
 		return ret;
diff --git a/drivers/vfio/platform/vfio_platform_common.c b/drivers/vfio/platform/vfio_platform_common.c
index e65b142..bf74e21 100644
--- a/drivers/vfio/platform/vfio_platform_common.c
+++ b/drivers/vfio/platform/vfio_platform_common.c
@@ -568,7 +568,7 @@ int vfio_platform_probe_common(struct vfio_platform_device *vdev,
 	}
 
 	ret = vfio_add_group_dev(dev, &vfio_platform_ops, vdev);
-	if (ret) {
+	if (ret < 0) {
 		iommu_group_put(group);
 		return ret;
 	}
diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 6fd6fa5..67db231 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -756,6 +756,7 @@ int vfio_add_group_dev(struct device *dev,
 	struct iommu_group *iommu_group;
 	struct vfio_group *group;
 	struct vfio_device *device;
+	int noiommu;
 
 	iommu_group = iommu_group_get(dev);
 	if (!iommu_group)
@@ -791,6 +792,8 @@ int vfio_add_group_dev(struct device *dev,
 		return PTR_ERR(device);
 	}
 
+	noiommu = group->noiommu;
+
 	/*
 	 * Drop all but the vfio_device reference.  The vfio_device holds
 	 * a reference to the vfio_group, which holds a reference to the
@@ -798,7 +801,7 @@ int vfio_add_group_dev(struct device *dev,
 	 */
 	vfio_group_put(group);
 
-	return 0;
+	return noiommu;
 }
 EXPORT_SYMBOL_GPL(vfio_add_group_dev);
 
diff --git a/Documentation/vfio.txt b/Documentation/vfio.txt
index 1dd3fdd..d76be0f 100644
--- a/Documentation/vfio.txt
+++ b/Documentation/vfio.txt
@@ -259,7 +259,9 @@ extern void *vfio_del_group_dev(struct device *dev);
 
 vfio_add_group_dev() indicates to the core to begin tracking the
 specified iommu_group and register the specified dev as owned by
-a VFIO bus driver.  The driver provides an ops structure for callbacks
+a VFIO bus driver.  A negative return value indicates failure.
+A positive return value indicates that an unsafe noiommu mode
+is in use.  The driver provides an ops structure for callbacks
 similar to a file operations structure:
 
 struct vfio_device_ops {
-- 
MST