diff mbox series

[v4,5/5] vfio: Support IO page table replacement

Message ID 600343ffb282ff3bed5eb98a9255c0084d01a859.1678284812.git.nicolinc@nvidia.com
State New
Headers
Series Add IO page table replacement support |

Commit Message

Nicolin Chen March 8, 2023, 2:26 p.m. UTC 
  Now both the physical path and the emulated path should support an IO page
table replacement.

Call iommufd_device_replace() when vdev->iommufd_attached is true.

Also update the VFIO_DEVICE_ATTACH_IOMMUFD_PT kdoc in the uAPI header.

Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
---
 drivers/vfio/iommufd.c    | 6 +++---
 include/uapi/linux/vfio.h | 6 ++++++
 2 files changed, 9 insertions(+), 3 deletions(-)

Comments

Tian, Kevin March 10, 2023, 11:53 a.m. UTC | #1 
> From: Nicolin Chen <nicolinc@nvidia.com>
> Sent: Wednesday, March 8, 2023 10:26 PM
> 
> Now both the physical path and the emulated path should support an IO
> page
> table replacement.
> 
> Call iommufd_device_replace() when vdev->iommufd_attached is true.
> 

why is replace enabled only in physical path in this patch?
Nicolin Chen March 10, 2023, 11:38 p.m. UTC | #2 
On Fri, Mar 10, 2023 at 11:53:56AM +0000, Tian, Kevin wrote:
> External email: Use caution opening links or attachments
> 
> 
> > From: Nicolin Chen <nicolinc@nvidia.com>
> > Sent: Wednesday, March 8, 2023 10:26 PM
> >
> > Now both the physical path and the emulated path should support an IO
> > page
> > table replacement.
> >
> > Call iommufd_device_replace() when vdev->iommufd_attached is true.
> >
> 
> why is replace enabled only in physical path in this patch?

The emulated pathway does not call iommufd_device_attach() but
iommufd_access_set_ioas() in the other patch, which internally
takes care of the replacement for the access pointer.

Thanks
Nic
Tian, Kevin March 13, 2023, 2:04 a.m. UTC | #3 
> From: Nicolin Chen <nicolinc@nvidia.com>
> Sent: Saturday, March 11, 2023 7:38 AM
> 
> On Fri, Mar 10, 2023 at 11:53:56AM +0000, Tian, Kevin wrote:
> > External email: Use caution opening links or attachments
> >
> >
> > > From: Nicolin Chen <nicolinc@nvidia.com>
> > > Sent: Wednesday, March 8, 2023 10:26 PM
> > >
> > > Now both the physical path and the emulated path should support an IO
> > > page
> > > table replacement.
> > >
> > > Call iommufd_device_replace() when vdev->iommufd_attached is true.
> > >
> >
> > why is replace enabled only in physical path in this patch?
> 
> The emulated pathway does not call iommufd_device_attach() but
> iommufd_access_set_ioas() in the other patch, which internally
> takes care of the replacement for the access pointer.
> 

I thought there is a similar check as in physical path which should
be removed:

	if (vdev->iommufd_attached)
-		return -EBUSY;

but looks it's not the case for the emulated path.
diff mbox series

Patch

diff --git a/drivers/vfio/iommufd.c b/drivers/vfio/iommufd.c
index 8a9457d0a33c..a245a8e0c8ab 100644
--- a/drivers/vfio/iommufd.c
+++ b/drivers/vfio/iommufd.c
@@ -145,9 +145,9 @@  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;
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 692156a708bb..14375826a25b 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