Re: [PATCH V3 4/7] mdev: introduce device specific ops

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On 2019/10/15 下午6:41, Cornelia Huck wrote:
On Fri, 11 Oct 2019 16:15:54 +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       | 22 +++++---
  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                 |  9 +++-
  drivers/vfio/mdev/mdev_private.h              |  1 +
  drivers/vfio/mdev/vfio_mdev.c                 | 37 ++++++-------
  include/linux/mdev.h                          | 42 +++------------
  include/linux/vfio_mdev.h                     | 52 +++++++++++++++++++
  samples/vfio-mdev/mbochs.c                    | 20 ++++---
  samples/vfio-mdev/mdpy.c                      | 21 +++++---
  samples/vfio-mdev/mtty.c                      | 18 ++++---
  13 files changed, 177 insertions(+), 96 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 2035e48da7b2..553574ebba73 100644
--- a/Documentation/driver-api/vfio-mediated-device.rst
+++ b/Documentation/driver-api/vfio-mediated-device.rst
@@ -152,11 +152,20 @@ 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:
+In order to support multiple types of device/driver, device needs to
+provide both class_id and device_ops through:
"As multiple types of mediated devices may be supported, the device
needs to set up the class id and the device specific callbacks via:"

?

-* open: open callback of mediated device
-* close: close callback of mediated device
-* ioctl: ioctl callback of mediated device
+    void mdev_set_class(struct mdev_device *mdev, u16 id, const void *ops);
+
+The class_id is used to be paired with ids in id_table in mdev_driver
+structure for probing the correct driver.
"The class id  (specified in id) is used to match a device with an mdev
driver via its id table."

?

The device_ops is device
+specific callbacks which can be get through mdev_get_dev_ops()
+function by mdev bus driver.
"The device specific callbacks (specified in *ops) are obtainable via
mdev_get_dev_ops() (for use by the mdev bus driver.)"

?

For vfio-mdev device, its device specific
+ops are as follows:
"A vfio-mdev device (class id MDEV_ID_VFIO) uses the following
device-specific ops:"

?


All you propose is better than what I wrote, will change the docs.



+
+* 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
@@ -167,9 +176,10 @@ 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 through::
+It is also required to specify the class_id and device specific ops through::
- extern int mdev_set_class(struct device *dev, u16 id);
+	extern int mdev_set_class(struct device *dev, u16 id,
+	                          const void *ops);
Apologies if that has already been discussed, but do we want a 1:1
relationship between id and ops, or can different devices with the same
id register different ops?


I think we have a N:1 mapping between id and ops, e.g we want both virtio-mdev and vhost-mdev use a single set of device ops.

Thanks


If the former, would it make sense to first
register the ops for an id (once), and then have the ->create callback
only set the class id (with the core doing the lookup of the ops)?

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::
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