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Message-ID: <20191024134636.253131c5@x1.home>
Date: Thu, 24 Oct 2019 13:46:36 -0600
From: Alex Williamson <alex.williamson@...hat.com>
To: Jason Wang <jasowang@...hat.com>
Cc: kvm@...r.kernel.org, linux-s390@...r.kernel.org,
linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
intel-gfx@...ts.freedesktop.org,
intel-gvt-dev@...ts.freedesktop.org, kwankhede@...dia.com,
mst@...hat.com, tiwei.bie@...el.com,
virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
cohuck@...hat.com, maxime.coquelin@...hat.com,
cunming.liang@...el.com, zhihong.wang@...el.com,
rob.miller@...adcom.com, xiao.w.wang@...el.com,
haotian.wang@...ive.com, zhenyuw@...ux.intel.com,
zhi.a.wang@...el.com, jani.nikula@...ux.intel.com,
joonas.lahtinen@...ux.intel.com, rodrigo.vivi@...el.com,
airlied@...ux.ie, daniel@...ll.ch, farman@...ux.ibm.com,
pasic@...ux.ibm.com, sebott@...ux.ibm.com, oberpar@...ux.ibm.com,
heiko.carstens@...ibm.com, gor@...ux.ibm.com,
borntraeger@...ibm.com, akrowiak@...ux.ibm.com,
freude@...ux.ibm.com, lingshan.zhu@...el.com, idos@...lanox.com,
eperezma@...hat.com, lulu@...hat.com, parav@...lanox.com,
christophe.de.dinechin@...il.com, kevin.tian@...el.com,
stefanha@...hat.com
Subject: Re: [PATCH V5 1/6] mdev: class id support
On Thu, 24 Oct 2019 11:27:36 +0800
Jason Wang <jasowang@...hat.com> wrote:
> On 2019/10/24 上午5:42, Alex Williamson wrote:
> > On Wed, 23 Oct 2019 21:07:47 +0800
> > Jason Wang <jasowang@...hat.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@...hat.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
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