Re: [PATCH V4 3/6] mdev: introduce device specific ops

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On 2019/10/17 下午11:07, Cornelia Huck wrote:
On Thu, 17 Oct 2019 18:48:33 +0800
Jason Wang <jasowang@xxxxxxxxxx> wrote:

Currently, except for the create and remove, the rest of
mdev_parent_ops is designed for vfio-mdev driver only and may not help
for kernel mdev driver. With the help of class id, this patch
introduces device specific callbacks inside mdev_device
structure. This allows different set of callback to be used by
vfio-mdev and virtio-mdev.

Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
---
  .../driver-api/vfio-mediated-device.rst       | 25 +++++----
  MAINTAINERS                                   |  1 +
  drivers/gpu/drm/i915/gvt/kvmgt.c              | 18 ++++---
  drivers/s390/cio/vfio_ccw_ops.c               | 18 ++++---
  drivers/s390/crypto/vfio_ap_ops.c             | 14 +++--
  drivers/vfio/mdev/mdev_core.c                 | 18 +++++--
  drivers/vfio/mdev/mdev_private.h              |  1 +
  drivers/vfio/mdev/vfio_mdev.c                 | 37 ++++++-------
  include/linux/mdev.h                          | 45 ++++------------
  include/linux/vfio_mdev.h                     | 52 +++++++++++++++++++
  samples/vfio-mdev/mbochs.c                    | 20 ++++---
  samples/vfio-mdev/mdpy.c                      | 20 ++++---
  samples/vfio-mdev/mtty.c                      | 18 ++++---
  13 files changed, 184 insertions(+), 103 deletions(-)
  create mode 100644 include/linux/vfio_mdev.h

diff --git a/Documentation/driver-api/vfio-mediated-device.rst b/Documentation/driver-api/vfio-mediated-device.rst
index f9a78d75a67a..0cca84d19603 100644
--- a/Documentation/driver-api/vfio-mediated-device.rst
+++ b/Documentation/driver-api/vfio-mediated-device.rst
@@ -152,11 +152,22 @@ callbacks per mdev parent device, per mdev type, or any other categorization.
  Vendor drivers are expected to be fully asynchronous in this respect or
  provide their own internal resource protection.)
-The callbacks in the mdev_parent_ops structure are as follows:
-
-* open: open callback of mediated device
-* close: close callback of mediated device
-* ioctl: ioctl callback of mediated device
+As multiple types of mediated devices may be supported, the device
+must set up the class id and the device specific callbacks in create()
s/in create()/in the create()/


Will fix.



+callback. E.g for vfio-mdev device it needs to be done through:
"Each class provides a helper function to do so; e.g. for vfio-mdev
devices, the function to be called is:"

?


This looks better.



+
+    int mdev_set_vfio_ops(struct mdev_device *mdev,
+                          const struct vfio_mdev_ops *vfio_ops);
+
+The class id (set to MDEV_CLASS_ID_VFIO) is used to match a device
"(set by this helper function to MDEV_CLASS_ID_VFIO)" ?


Yes.


+with an mdev driver via its id table. The device specific callbacks
+(specified in *ops) are obtainable via mdev_get_dev_ops() (for use by
"(specified in *vfio_ops by the caller)" ?


Yes.


+the mdev bus driver). A vfio-mdev device (class id MDEV_CLASS_ID_VFIO)
+uses the following device-specific ops:
+
+* open: open callback of vfio mediated device
+* close: close callback of vfio mediated device
+* ioctl: ioctl callback of vfio mediated device
  * read : read emulation callback
  * write: write emulation callback
  * mmap: mmap emulation callback
@@ -167,10 +178,6 @@ register itself with the mdev core driver::
  	extern int  mdev_register_device(struct device *dev,
  	                                 const struct mdev_parent_ops *ops);
-It is also required to specify the class_id in create() callback through::
-
-	int mdev_set_class(struct mdev_device *mdev, u16 id);
-
I'm wondering if this patch set should start out with introducing
helper functions already (i.e. don't introduce mdev_set_class(), but
start out with mdev_set_class_vfio() which will gain the *vfio_ops
argument in this patch.)


I think it doesn't harm to keep it as is since in patch 1 we introduce class_id and bus match method based on that without device ops there.  But if you stick I can change.

Thanks



  However, the mdev_parent_ops structure is not required in the function call
  that a driver should use to unregister itself with the mdev core driver::
(...)

diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c
index 3a9c52d71b4e..d0f3113c8071 100644
--- a/drivers/vfio/mdev/mdev_core.c
+++ b/drivers/vfio/mdev/mdev_core.c
@@ -45,15 +45,23 @@ void mdev_set_drvdata(struct mdev_device *mdev, void *data)
  }
  EXPORT_SYMBOL(mdev_set_drvdata);
-/* Specify the class for the mdev device, this must be called during
- * create() callback.
+/* Specify the VFIO device ops for the mdev device, this
+ * must be called during create() callback for VFIO mdev device.
   */
/*
  * Specify the mdev device to be a VFIO mdev device, and set the
  * VFIO devices ops for it. This must be called from the create()
  * callback for VFIO mdev devices.
  */

?

-void mdev_set_class(struct mdev_device *mdev, u16 id)
+void mdev_set_vfio_ops(struct mdev_device *mdev,
+		       const struct vfio_mdev_device_ops *vfio_ops)
  {
  	WARN_ON(mdev->class_id);
-	mdev->class_id = id;
+	mdev->class_id = MDEV_CLASS_ID_VFIO;
+	mdev->device_ops = vfio_ops;
  }
-EXPORT_SYMBOL(mdev_set_class);
+EXPORT_SYMBOL(mdev_set_vfio_ops);
+
+const void *mdev_get_dev_ops(struct mdev_device *mdev)
+{
+	return mdev->device_ops;
+}
+EXPORT_SYMBOL(mdev_get_dev_ops);
struct device *mdev_dev(struct mdev_device *mdev)
  {
(...)

The code change looks good to me; I'm just wondering if we should
introduce mdev_set_class() at all (see above).
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