Re: [PATCH V5 1/6] mdev: class id support

From: Jason Wang
Date: Thu Oct 24 2019 - 21:43:12 EST

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In reply to: Alex Williamson: "Re: [PATCH V5 1/6] mdev: class id support"
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On 2019/10/25 äå4:13, Alex Williamson wrote:

On Thu, 24 Oct 2019 13:46:36 -0600
Alex Williamson <alex.williamson@xxxxxxxxxx> wrote:

On Thu, 24 Oct 2019 11:27:36 +0800
Jason Wang <jasowang@xxxxxxxxxx> wrote:

On 2019/10/24 äå5:42, Alex Williamson wrote:

On Wed, 23 Oct 2019 21:07:47 +0800
Jason Wang <jasowang@xxxxxxxxxx> wrote:

Mdev bus only supports vfio driver right now, so it doesn't implement
match method. But in the future, we may add drivers other than vfio,
the first driver could be virtio-mdev. This means we need to add
device class id support in bus match method to pair the mdev device
and mdev driver correctly.

So this patch adds id_table to mdev_driver and class_id for mdev
device with the match method for mdev bus.

Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
---
.../driver-api/vfio-mediated-device.rst | 5 +++++
drivers/gpu/drm/i915/gvt/kvmgt.c | 1 +
drivers/s390/cio/vfio_ccw_ops.c | 1 +
drivers/s390/crypto/vfio_ap_ops.c | 1 +
drivers/vfio/mdev/mdev_core.c | 18 +++++++++++++++
drivers/vfio/mdev/mdev_driver.c | 22 +++++++++++++++++++
drivers/vfio/mdev/mdev_private.h | 1 +
drivers/vfio/mdev/vfio_mdev.c | 6 +++++
include/linux/mdev.h | 8 +++++++
include/linux/mod_devicetable.h | 8 +++++++
samples/vfio-mdev/mbochs.c | 1 +
samples/vfio-mdev/mdpy.c | 1 +
samples/vfio-mdev/mtty.c | 1 +
13 files changed, 74 insertions(+)

diff --git a/Documentation/driver-api/vfio-mediated-device.rst b/Documentation/driver-api/vfio-mediated-device.rst
index 25eb7d5b834b..6709413bee29 100644
--- a/Documentation/driver-api/vfio-mediated-device.rst
+++ b/Documentation/driver-api/vfio-mediated-device.rst
@@ -102,12 +102,14 @@ structure to represent a mediated device's driver::
* @probe: called when new device created
* @remove: called when device removed
* @driver: device driver structure
+ * @id_table: the ids serviced by this driver
*/
struct mdev_driver {
const char *name;
int (*probe) (struct device *dev);
void (*remove) (struct device *dev);
struct device_driver driver;
+ const struct mdev_class_id *id_table;
};
A mediated bus driver for mdev should use this structure in the function calls
@@ -170,6 +172,9 @@ that a driver should use to unregister itself with the mdev core driver::
extern void mdev_unregister_device(struct device *dev);
+It is also required to specify the class_id in create() callback through::
+
+ int mdev_set_class(struct mdev_device *mdev, u16 id);
Mediated Device Management Interface Through sysfs
==================================================
diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
index 343d79c1cb7e..6420f0dbd31b 100644
--- a/drivers/gpu/drm/i915/gvt/kvmgt.c
+++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
@@ -678,6 +678,7 @@ static int intel_vgpu_create(struct kobject *kobj, struct mdev_device *mdev)
dev_name(mdev_dev(mdev)));
ret = 0;
+ mdev_set_class(mdev, MDEV_CLASS_ID_VFIO);
out:
return ret;
}
diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_ops.c
index f0d71ab77c50..cf2c013ae32f 100644
--- a/drivers/s390/cio/vfio_ccw_ops.c
+++ b/drivers/s390/cio/vfio_ccw_ops.c
@@ -129,6 +129,7 @@ static int vfio_ccw_mdev_create(struct kobject *kobj, struct mdev_device *mdev)
private->sch->schid.ssid,
private->sch->schid.sch_no);
+ mdev_set_class(mdev, MDEV_CLASS_ID_VFIO);
return 0;
}
diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index 5c0f53c6dde7..07c31070afeb 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -343,6 +343,7 @@ static int vfio_ap_mdev_create(struct kobject *kobj, struct mdev_device *mdev)
list_add(&matrix_mdev->node, &matrix_dev->mdev_list);
mutex_unlock(&matrix_dev->lock);
+ mdev_set_class(mdev, MDEV_CLASS_ID_VFIO);
return 0;
}
diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c
index b558d4cfd082..3a9c52d71b4e 100644
--- a/drivers/vfio/mdev/mdev_core.c
+++ b/drivers/vfio/mdev/mdev_core.c
@@ -45,6 +45,16 @@ 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.
+ */
+void mdev_set_class(struct mdev_device *mdev, u16 id)
+{
+ WARN_ON(mdev->class_id);
+ mdev->class_id = id;
+}
+EXPORT_SYMBOL(mdev_set_class);
+
struct device *mdev_dev(struct mdev_device *mdev)
{
return &mdev->dev;
@@ -135,6 +145,7 @@ static int mdev_device_remove_cb(struct device *dev, void *data)
* mdev_register_device : Register a device
* @dev: device structure representing parent device.
* @ops: Parent device operation structure to be registered.
+ * @id: class id.
*
* Add device to list of registered parent devices.
* Returns a negative value on error, otherwise 0.
@@ -324,6 +335,13 @@ int mdev_device_create(struct kobject *kobj,
if (ret)
goto ops_create_fail;
+ if (!mdev->class_id) {
+ ret = -EINVAL;
+ WARN(1, "class id must be specified for device %s\n",
+ dev_name(dev));

Nit, dev_warn(dev, "mdev vendor driver failed to specify device class\n");

Will fix.

+ goto add_fail;
+ }
+
ret = device_add(&mdev->dev);
if (ret)
goto add_fail;
diff --git a/drivers/vfio/mdev/mdev_driver.c b/drivers/vfio/mdev/mdev_driver.c
index 0d3223aee20b..319d886ffaf7 100644
--- a/drivers/vfio/mdev/mdev_driver.c
+++ b/drivers/vfio/mdev/mdev_driver.c
@@ -69,8 +69,30 @@ static int mdev_remove(struct device *dev)
return 0;
}
+static int mdev_match(struct device *dev, struct device_driver *drv)
+{
+ unsigned int i;
+ struct mdev_device *mdev = to_mdev_device(dev);
+ struct mdev_driver *mdrv = to_mdev_driver(drv);
+ const struct mdev_class_id *ids = mdrv->id_table;
+

Nit, as we start to allow new mdev bus drivers, mdev-core might want to
protect itself from a NULL id_table, by either failing the
mdev_register_driver() or failing the match here. I think such a
condition would segfault as written here, but clearly we don't have
such external drivers yet. Thanks,

I'm not sure I get the point here. My understanding is that mdev-core
won't try to be matched here since it was not a complete mdev device.

The parent driver failing to set a type vs the parent driver failing to

Correction, the second half of this should be in reference to the mdev
bus driver.

register with a struct mdev_driver where id_table is not null are
different issues. I agree that if a vendor driver was not updated for
this series that they'd never successfully create a device because the
mdev-core would reject it for not setting a class, but mdev_match() is
called for devices that might be created by other vendor drivers, so
loading a parent driver with a null id_table potentially breaks
matching for everyone. Thanks,

The point is still valid though, for example if vfio-mdev registered
with a null id_table it would break matching for virtio-mdev depending
on the order we iterate through drivers as we call mdev_match().
Thanks,

Alex

I see the point, so I can check the existence of id_table before trying to do the match here.

Thanks

Next message: Jason Wang: "Re: [PATCH V5 2/6] modpost: add support for mdev class id"
Previous message: Steven Rostedt: "Re: [PATCH v2 16/17] arm64: disable SCS for hypervisor code"
In reply to: Alex Williamson: "Re: [PATCH V5 1/6] mdev: class id support"
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