[PATCH v6 4/4] vfio: Support IO page table replacement

Nicolin Chen
2023-03-27T18:05:58Z

Now both the physical path and the emulated path should support an IO page
table replacement. Call iommufd_device_replace/iommufd_access_replace(),
when vdev->iommufd_attached is true.

Also update the VFIO_DEVICE_ATTACH_IOMMUFD_PT kdoc in the uAPI header.

Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
---
drivers/vfio/iommufd.c | 11 ++++++-----
include/uapi/linux/vfio.h | 6 ++++++
2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/drivers/vfio/iommufd.c b/drivers/vfio/iommufd.c
index df4d6e0739b5..2d97424be582 100644
--- a/drivers/vfio/iommufd.c
+++ b/drivers/vfio/iommufd.c
@@ -121,9 +121,9 @@ int vfio_iommufd_physical_attach_ioas(struct vfio_device *vdev, u32 *pt_id)
return -EINVAL;

if (vdev->iommufd_attached)
- return -EBUSY;
-
- rc = iommufd_device_attach(vdev->iommufd_device, pt_id);
+ rc = iommufd_device_replace(vdev->iommufd_device, pt_id);
+ else
+ rc = iommufd_device_attach(vdev->iommufd_device, pt_id);
if (rc)
return rc;
vdev->iommufd_attached = true;
@@ -198,8 +198,9 @@ int vfio_iommufd_emulated_attach_ioas(struct vfio_device *vdev, u32 *pt_id)
lockdep_assert_held(&vdev->dev_set->lock);

if (vdev->iommufd_attached)
- return -EBUSY;
- rc = iommufd_access_attach(vdev->iommufd_access, *pt_id);
+ rc = iommufd_access_replace(vdev->iommufd_access, *pt_id);
+ else
+ rc = iommufd_access_attach(vdev->iommufd_access, *pt_id);
if (rc)
return rc;
vdev->iommufd_attached = true;
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index bf6c97e759c7..e067cc5ab0e5 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -243,6 +243,12 @@ struct vfio_device_bind_iommufd {
*
* Undo by VFIO_DEVICE_DETACH_IOMMUFD_PT or device fd close.
*
+ * If a vfio device is currently attached to a valid hw_pagetable, without doing
+ * a VFIO_DEVICE_DETACH_IOMMUFD_PT, a second VFIO_DEVICE_ATTACH_IOMMUFD_PT ioctl
+ * passing in another hw_pagetable (hwpt) id is allowed. This action, also known
+ * as a hw_pagetable replacement, will replace the device's currently attached
+ * hw_pagetable with a new hw_pagetable corresponding to the given pt_id.
+ *
* @argsz: user filled size of this data.
* @flags: must be 0.
* @pt_id: Input the target id which can represent an ioas or a hwpt
--
2.40.0