On Thu, 24 Oct 2019 11:27:36 +0800 Jason Wang <jasowang at redhat.com> wrote:> On 2019/10/24 ??5:42, Alex Williamson wrote: > > On Wed, 23 Oct 2019 21:07:47 +0800 > > Jason Wang <jasowang at redhat.com> 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 at redhat.com> > >> --- > >> .../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 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, Alex
On Thu, 24 Oct 2019 13:46:36 -0600 Alex Williamson <alex.williamson at redhat.com> wrote:> On Thu, 24 Oct 2019 11:27:36 +0800 > Jason Wang <jasowang at redhat.com> wrote: > > > On 2019/10/24 ??5:42, Alex Williamson wrote: > > > On Wed, 23 Oct 2019 21:07:47 +0800 > > > Jason Wang <jasowang at redhat.com> 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 at redhat.com> > > >> --- > > >> .../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 toCorrection, 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
On 2019/10/25 ??4:13, Alex Williamson wrote:> On Thu, 24 Oct 2019 13:46:36 -0600 > Alex Williamson <alex.williamson at redhat.com> wrote: > >> On Thu, 24 Oct 2019 11:27:36 +0800 >> Jason Wang <jasowang at redhat.com> wrote: >> >>> On 2019/10/24 ??5:42, Alex Williamson wrote: >>>> On Wed, 23 Oct 2019 21:07:47 +0800 >>>> Jason Wang <jasowang at redhat.com> 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 at redhat.com> >>>>> --- >>>>> .../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, > > AlexI see the point, so I can check the existence of id_table before trying to do the match here. Thanks