[RFC] vhost_mdev: add network control vq support

[RFC] vhost_mdev: add network control vq support

[Tiwei Bie]

This patch adds the network control vq support in vhost-mdev.
A vhost-mdev specific op is introduced to allow parent drivers
to handle the network control commands come from userspace.

Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
---
This patch depends on below patch:
https://lkml.org/lkml/2019/10/29/335

 drivers/vhost/mdev.c             | 37 ++++++++++++++++++++++++++++++--
 include/linux/virtio_mdev_ops.h  | 10 +++++++++
 include/uapi/linux/vhost.h       |  7 ++++++
 include/uapi/linux/vhost_types.h |  6 ++++++
 4 files changed, 58 insertions(+), 2 deletions(-)

diff --git a/drivers/vhost/mdev.c b/drivers/vhost/mdev.c
index 35b2fb33e686..c9b3eaa77405 100644
--- a/drivers/vhost/mdev.c
+++ b/drivers/vhost/mdev.c
@@ -47,6 +47,13 @@ enum {
 		(1ULL << VIRTIO_NET_F_HOST_UFO) |
 		(1ULL << VIRTIO_NET_F_MRG_RXBUF) |
 		(1ULL << VIRTIO_NET_F_STATUS) |
+		(1ULL << VIRTIO_NET_F_CTRL_GUEST_OFFLOADS) |
+		(1ULL << VIRTIO_NET_F_CTRL_VQ) |
+		(1ULL << VIRTIO_NET_F_CTRL_RX) |
+		(1ULL << VIRTIO_NET_F_CTRL_VLAN) |
+		(1ULL << VIRTIO_NET_F_CTRL_RX_EXTRA) |
+		(1ULL << VIRTIO_NET_F_GUEST_ANNOUNCE) |
+		(1ULL << VIRTIO_NET_F_CTRL_MAC_ADDR) |
 		(1ULL << VIRTIO_NET_F_SPEED_DUPLEX),
 };
 
@@ -362,6 +369,29 @@ static long vhost_mdev_vring_ioctl(struct vhost_mdev *m, unsigned int cmd,
 	return r;
 }
 
+/*
+ * Device specific (e.g. network) ioctls.
+ */
+static long vhost_mdev_dev_ioctl(struct vhost_mdev *m, unsigned int cmd,
+				 void __user *argp)
+{
+	struct mdev_device *mdev = m->mdev;
+	const struct virtio_mdev_device_ops *ops = mdev_get_vhost_ops(mdev);
+
+	switch (m->virtio_id) {
+	case VIRTIO_ID_NET:
+		switch (cmd) {
+		case VHOST_MDEV_NET_CTRL:
+			if (!ops->net.ctrl)
+				return -ENOTSUPP;
+			return ops->net.ctrl(mdev, argp);
+		}
+		break;
+	}
+
+	return -ENOIOCTLCMD;
+}
+
 static int vhost_mdev_open(void *device_data)
 {
 	struct vhost_mdev *m = device_data;
@@ -460,8 +490,11 @@ static long vhost_mdev_unlocked_ioctl(void *device_data,
 		 * VHOST_SET_LOG_FD are not used yet.
 		 */
 		r = vhost_dev_ioctl(&m->dev, cmd, argp);
-		if (r == -ENOIOCTLCMD)
-			r = vhost_mdev_vring_ioctl(m, cmd, argp);
+		if (r == -ENOIOCTLCMD) {
+			r = vhost_mdev_dev_ioctl(m, cmd, argp);
+			if (r == -ENOIOCTLCMD)
+				r = vhost_mdev_vring_ioctl(m, cmd, argp);
+		}
 	}
 
 	mutex_unlock(&m->mutex);
diff --git a/include/linux/virtio_mdev_ops.h b/include/linux/virtio_mdev_ops.h
index d417b41f2845..622861804ebd 100644
--- a/include/linux/virtio_mdev_ops.h
+++ b/include/linux/virtio_mdev_ops.h
@@ -20,6 +20,8 @@ struct virtio_mdev_callback {
 	void *private;
 };
 
+struct vhost_mdev_net_ctrl;
+
 /**
  * struct vfio_mdev_device_ops - Structure to be registered for each
  * mdev device to register the device for virtio/vhost drivers.
@@ -151,6 +153,14 @@ struct virtio_mdev_device_ops {
 
 	/* Mdev device ops */
 	u64 (*get_mdev_features)(struct mdev_device *mdev);
+
+	/* Vhost-mdev (MDEV_CLASS_ID_VHOST) specific ops */
+	union {
+		struct {
+			int (*ctrl)(struct mdev_device *mdev,
+				    struct vhost_mdev_net_ctrl __user *ctrl);
+		} net;
+	};
 };
 
 void mdev_set_virtio_ops(struct mdev_device *mdev,
diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
index 061a2824a1b3..3693b2cba0c4 100644
--- a/include/uapi/linux/vhost.h
+++ b/include/uapi/linux/vhost.h
@@ -134,4 +134,11 @@
 /* Get the max ring size. */
 #define VHOST_MDEV_GET_VRING_NUM	_IOR(VHOST_VIRTIO, 0x76, __u16)
 
+/* VHOST_MDEV device specific defines */
+
+/* Send virtio-net commands. The commands follow the same definition
+ * of the virtio-net commands defined in virtio-spec.
+ */
+#define VHOST_MDEV_NET_CTRL		_IOW(VHOST_VIRTIO, 0x77, struct vhost_mdev_net_ctrl *)
+
 #endif
diff --git a/include/uapi/linux/vhost_types.h b/include/uapi/linux/vhost_types.h
index 7b105d0b2fb9..e76b4d8e35e5 100644
--- a/include/uapi/linux/vhost_types.h
+++ b/include/uapi/linux/vhost_types.h
@@ -127,6 +127,12 @@ struct vhost_mdev_config {
 	__u8 buf[0];
 };
 
+struct vhost_mdev_net_ctrl {
+	__u8 class;
+	__u8 cmd;
+	__u8 cmd_data[0];
+} __attribute__((packed));
+
 /* Feature bits */
 /* Log all write descriptors. Can be changed while device is active. */
 #define VHOST_F_LOG_ALL 26
-- 
2.23.0

Re: [RFC] vhost_mdev: add network control vq support

[Jason Wang]

On 2019/10/29 下午6:17, Tiwei Bie wrote:
> This patch adds the network control vq support in vhost-mdev.
> A vhost-mdev specific op is introduced to allow parent drivers
> to handle the network control commands come from userspace.


Probably work for userspace driver but not kernel driver.


>
> Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
> ---
> This patch depends on below patch:
> https://lkml.org/lkml/2019/10/29/335
>
>  drivers/vhost/mdev.c             | 37 ++++++++++++++++++++++++++++++--
>  include/linux/virtio_mdev_ops.h  | 10 +++++++++
>  include/uapi/linux/vhost.h       |  7 ++++++
>  include/uapi/linux/vhost_types.h |  6 ++++++
>  4 files changed, 58 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/vhost/mdev.c b/drivers/vhost/mdev.c
> index 35b2fb33e686..c9b3eaa77405 100644
> --- a/drivers/vhost/mdev.c
> +++ b/drivers/vhost/mdev.c
> @@ -47,6 +47,13 @@ enum {
>  		(1ULL << VIRTIO_NET_F_HOST_UFO) |
>  		(1ULL << VIRTIO_NET_F_MRG_RXBUF) |
>  		(1ULL << VIRTIO_NET_F_STATUS) |
> +		(1ULL << VIRTIO_NET_F_CTRL_GUEST_OFFLOADS) |
> +		(1ULL << VIRTIO_NET_F_CTRL_VQ) |
> +		(1ULL << VIRTIO_NET_F_CTRL_RX) |
> +		(1ULL << VIRTIO_NET_F_CTRL_VLAN) |
> +		(1ULL << VIRTIO_NET_F_CTRL_RX_EXTRA) |
> +		(1ULL << VIRTIO_NET_F_GUEST_ANNOUNCE) |
> +		(1ULL << VIRTIO_NET_F_CTRL_MAC_ADDR) |
>  		(1ULL << VIRTIO_NET_F_SPEED_DUPLEX),
>  };
>  
> @@ -362,6 +369,29 @@ static long vhost_mdev_vring_ioctl(struct vhost_mdev *m, unsigned int cmd,
>  	return r;
>  }
>  
> +/*
> + * Device specific (e.g. network) ioctls.
> + */
> +static long vhost_mdev_dev_ioctl(struct vhost_mdev *m, unsigned int cmd,
> +				 void __user *argp)
> +{
> +	struct mdev_device *mdev = m->mdev;
> +	const struct virtio_mdev_device_ops *ops = mdev_get_vhost_ops(mdev);
> +
> +	switch (m->virtio_id) {
> +	case VIRTIO_ID_NET:
> +		switch (cmd) {
> +		case VHOST_MDEV_NET_CTRL:
> +			if (!ops->net.ctrl)
> +				return -ENOTSUPP;
> +			return ops->net.ctrl(mdev, argp);
> +		}
> +		break;
> +	}
> +
> +	return -ENOIOCTLCMD;
> +}


As you comment above, then vhost-mdev need device specific stuffs.


> +
>  static int vhost_mdev_open(void *device_data)
>  {
>  	struct vhost_mdev *m = device_data;
> @@ -460,8 +490,11 @@ static long vhost_mdev_unlocked_ioctl(void *device_data,
>  		 * VHOST_SET_LOG_FD are not used yet.
>  		 */
>  		r = vhost_dev_ioctl(&m->dev, cmd, argp);
> -		if (r == -ENOIOCTLCMD)
> -			r = vhost_mdev_vring_ioctl(m, cmd, argp);
> +		if (r == -ENOIOCTLCMD) {
> +			r = vhost_mdev_dev_ioctl(m, cmd, argp);
> +			if (r == -ENOIOCTLCMD)
> +				r = vhost_mdev_vring_ioctl(m, cmd, argp);
> +		}
>  	}
>  
>  	mutex_unlock(&m->mutex);
> diff --git a/include/linux/virtio_mdev_ops.h b/include/linux/virtio_mdev_ops.h
> index d417b41f2845..622861804ebd 100644
> --- a/include/linux/virtio_mdev_ops.h
> +++ b/include/linux/virtio_mdev_ops.h
> @@ -20,6 +20,8 @@ struct virtio_mdev_callback {
>  	void *private;
>  };
>  
> +struct vhost_mdev_net_ctrl;
> +
>  /**
>   * struct vfio_mdev_device_ops - Structure to be registered for each
>   * mdev device to register the device for virtio/vhost drivers.
> @@ -151,6 +153,14 @@ struct virtio_mdev_device_ops {
>  
>  	/* Mdev device ops */
>  	u64 (*get_mdev_features)(struct mdev_device *mdev);
> +
> +	/* Vhost-mdev (MDEV_CLASS_ID_VHOST) specific ops */
> +	union {
> +		struct {
> +			int (*ctrl)(struct mdev_device *mdev,
> +				    struct vhost_mdev_net_ctrl __user *ctrl);
> +		} net;
> +	};


And so did device_ops. I still think we'd try out best to avoid such thing.

Thanks


>  };
>  
>  void mdev_set_virtio_ops(struct mdev_device *mdev,
> diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
> index 061a2824a1b3..3693b2cba0c4 100644
> --- a/include/uapi/linux/vhost.h
> +++ b/include/uapi/linux/vhost.h
> @@ -134,4 +134,11 @@
>  /* Get the max ring size. */
>  #define VHOST_MDEV_GET_VRING_NUM	_IOR(VHOST_VIRTIO, 0x76, __u16)
>  
> +/* VHOST_MDEV device specific defines */
> +
> +/* Send virtio-net commands. The commands follow the same definition
> + * of the virtio-net commands defined in virtio-spec.
> + */
> +#define VHOST_MDEV_NET_CTRL		_IOW(VHOST_VIRTIO, 0x77, struct vhost_mdev_net_ctrl *)
> +
>  #endif
> diff --git a/include/uapi/linux/vhost_types.h b/include/uapi/linux/vhost_types.h
> index 7b105d0b2fb9..e76b4d8e35e5 100644
> --- a/include/uapi/linux/vhost_types.h
> +++ b/include/uapi/linux/vhost_types.h
> @@ -127,6 +127,12 @@ struct vhost_mdev_config {
>  	__u8 buf[0];
>  };
>  
> +struct vhost_mdev_net_ctrl {
> +	__u8 class;
> +	__u8 cmd;
> +	__u8 cmd_data[0];
> +} __attribute__((packed));
> +
>  /* Feature bits */
>  /* Log all write descriptors. Can be changed while device is active. */
>  #define VHOST_F_LOG_ALL 26

Re: [RFC] vhost_mdev: add network control vq support

[Tiwei Bie]

On Tue, Oct 29, 2019 at 06:51:32PM +0800, Jason Wang wrote:
> On 2019/10/29 下午6:17, Tiwei Bie wrote:
> > This patch adds the network control vq support in vhost-mdev.
> > A vhost-mdev specific op is introduced to allow parent drivers
> > to handle the network control commands come from userspace.
> 
> Probably work for userspace driver but not kernel driver.

Exactly. This is only for userspace.

I got your point now. In virtio-mdev kernel driver case,
the ctrl-vq can be special as well.

> 
> 
> >
> > Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
> > ---
> > This patch depends on below patch:
> > https://lkml.org/lkml/2019/10/29/335
> >
> >  drivers/vhost/mdev.c             | 37 ++++++++++++++++++++++++++++++--
> >  include/linux/virtio_mdev_ops.h  | 10 +++++++++
> >  include/uapi/linux/vhost.h       |  7 ++++++
> >  include/uapi/linux/vhost_types.h |  6 ++++++
> >  4 files changed, 58 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/vhost/mdev.c b/drivers/vhost/mdev.c
> > index 35b2fb33e686..c9b3eaa77405 100644
> > --- a/drivers/vhost/mdev.c
> > +++ b/drivers/vhost/mdev.c
> > @@ -47,6 +47,13 @@ enum {
> >  		(1ULL << VIRTIO_NET_F_HOST_UFO) |
> >  		(1ULL << VIRTIO_NET_F_MRG_RXBUF) |
> >  		(1ULL << VIRTIO_NET_F_STATUS) |
> > +		(1ULL << VIRTIO_NET_F_CTRL_GUEST_OFFLOADS) |
> > +		(1ULL << VIRTIO_NET_F_CTRL_VQ) |
> > +		(1ULL << VIRTIO_NET_F_CTRL_RX) |
> > +		(1ULL << VIRTIO_NET_F_CTRL_VLAN) |
> > +		(1ULL << VIRTIO_NET_F_CTRL_RX_EXTRA) |
> > +		(1ULL << VIRTIO_NET_F_GUEST_ANNOUNCE) |
> > +		(1ULL << VIRTIO_NET_F_CTRL_MAC_ADDR) |
> >  		(1ULL << VIRTIO_NET_F_SPEED_DUPLEX),
> >  };
> >  
> > @@ -362,6 +369,29 @@ static long vhost_mdev_vring_ioctl(struct vhost_mdev *m, unsigned int cmd,
> >  	return r;
> >  }
> >  
> > +/*
> > + * Device specific (e.g. network) ioctls.
> > + */
> > +static long vhost_mdev_dev_ioctl(struct vhost_mdev *m, unsigned int cmd,
> > +				 void __user *argp)
> > +{
> > +	struct mdev_device *mdev = m->mdev;
> > +	const struct virtio_mdev_device_ops *ops = mdev_get_vhost_ops(mdev);
> > +
> > +	switch (m->virtio_id) {
> > +	case VIRTIO_ID_NET:
> > +		switch (cmd) {
> > +		case VHOST_MDEV_NET_CTRL:
> > +			if (!ops->net.ctrl)
> > +				return -ENOTSUPP;
> > +			return ops->net.ctrl(mdev, argp);
> > +		}
> > +		break;
> > +	}
> > +
> > +	return -ENOIOCTLCMD;
> > +}
> 
> As you comment above, then vhost-mdev need device specific stuffs.

Yeah. But this device specific stuff is quite small and
simple. It's just to forward the settings between parent
and userspace. But I totally agree it would be really
great if we could avoid it in an elegant way.

> 
> 
> > +
> >  static int vhost_mdev_open(void *device_data)
> >  {
> >  	struct vhost_mdev *m = device_data;
> > @@ -460,8 +490,11 @@ static long vhost_mdev_unlocked_ioctl(void *device_data,
> >  		 * VHOST_SET_LOG_FD are not used yet.
> >  		 */
> >  		r = vhost_dev_ioctl(&m->dev, cmd, argp);
> > -		if (r == -ENOIOCTLCMD)
> > -			r = vhost_mdev_vring_ioctl(m, cmd, argp);
> > +		if (r == -ENOIOCTLCMD) {
> > +			r = vhost_mdev_dev_ioctl(m, cmd, argp);
> > +			if (r == -ENOIOCTLCMD)
> > +				r = vhost_mdev_vring_ioctl(m, cmd, argp);
> > +		}
> >  	}
> >  
> >  	mutex_unlock(&m->mutex);
> > diff --git a/include/linux/virtio_mdev_ops.h b/include/linux/virtio_mdev_ops.h
> > index d417b41f2845..622861804ebd 100644
> > --- a/include/linux/virtio_mdev_ops.h
> > +++ b/include/linux/virtio_mdev_ops.h
> > @@ -20,6 +20,8 @@ struct virtio_mdev_callback {
> >  	void *private;
> >  };
> >  
> > +struct vhost_mdev_net_ctrl;
> > +
> >  /**
> >   * struct vfio_mdev_device_ops - Structure to be registered for each
> >   * mdev device to register the device for virtio/vhost drivers.
> > @@ -151,6 +153,14 @@ struct virtio_mdev_device_ops {
> >  
> >  	/* Mdev device ops */
> >  	u64 (*get_mdev_features)(struct mdev_device *mdev);
> > +
> > +	/* Vhost-mdev (MDEV_CLASS_ID_VHOST) specific ops */
> > +	union {
> > +		struct {
> > +			int (*ctrl)(struct mdev_device *mdev,
> > +				    struct vhost_mdev_net_ctrl __user *ctrl);
> > +		} net;
> > +	};
> 
> And so did device_ops. I still think we'd try out best to avoid such thing.

I totally agree we should try our best to avoid it.
But in this case, I think it may be worth considering
as it does simplify the userspace API and the parent
driver implementation a lot..


> 
> Thanks
> 
> 
> >  };
> >  
> >  void mdev_set_virtio_ops(struct mdev_device *mdev,
> > diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
> > index 061a2824a1b3..3693b2cba0c4 100644
> > --- a/include/uapi/linux/vhost.h
> > +++ b/include/uapi/linux/vhost.h
> > @@ -134,4 +134,11 @@
> >  /* Get the max ring size. */
> >  #define VHOST_MDEV_GET_VRING_NUM	_IOR(VHOST_VIRTIO, 0x76, __u16)
> >  
> > +/* VHOST_MDEV device specific defines */
> > +
> > +/* Send virtio-net commands. The commands follow the same definition
> > + * of the virtio-net commands defined in virtio-spec.
> > + */
> > +#define VHOST_MDEV_NET_CTRL		_IOW(VHOST_VIRTIO, 0x77, struct vhost_mdev_net_ctrl *)
> > +
> >  #endif
> > diff --git a/include/uapi/linux/vhost_types.h b/include/uapi/linux/vhost_types.h
> > index 7b105d0b2fb9..e76b4d8e35e5 100644
> > --- a/include/uapi/linux/vhost_types.h
> > +++ b/include/uapi/linux/vhost_types.h
> > @@ -127,6 +127,12 @@ struct vhost_mdev_config {
> >  	__u8 buf[0];
> >  };
> >  
> > +struct vhost_mdev_net_ctrl {
> > +	__u8 class;
> > +	__u8 cmd;
> > +	__u8 cmd_data[0];
> > +} __attribute__((packed));
> > +
> >  /* Feature bits */
> >  /* Log all write descriptors. Can be changed while device is active. */
> >  #define VHOST_F_LOG_ALL 26
> 

Re: [RFC] vhost_mdev: add network control vq support

[Jason Wang]

On 2019/10/30 下午2:17, Tiwei Bie wrote:
> On Tue, Oct 29, 2019 at 06:51:32PM +0800, Jason Wang wrote:
>> On 2019/10/29 下午6:17, Tiwei Bie wrote:
>>> This patch adds the network control vq support in vhost-mdev.
>>> A vhost-mdev specific op is introduced to allow parent drivers
>>> to handle the network control commands come from userspace.
>> Probably work for userspace driver but not kernel driver.
> Exactly. This is only for userspace.
>
> I got your point now. In virtio-mdev kernel driver case,
> the ctrl-vq can be special as well.
>

Then maybe it's better to introduce vhost-mdev-net on top?

Looking at the other type of virtio device:

- console have two control virtqueues when multiqueue port is enabled

- SCSI has controlq + eventq

- GPU has controlq

- Crypto device has one controlq

- Socket has eventq

...

Thanks

Re: [RFC] vhost_mdev: add network control vq support

[Tiwei Bie]

On Wed, Oct 30, 2019 at 03:04:37PM +0800, Jason Wang wrote:
> On 2019/10/30 下午2:17, Tiwei Bie wrote:
> > On Tue, Oct 29, 2019 at 06:51:32PM +0800, Jason Wang wrote:
> >> On 2019/10/29 下午6:17, Tiwei Bie wrote:
> >>> This patch adds the network control vq support in vhost-mdev.
> >>> A vhost-mdev specific op is introduced to allow parent drivers
> >>> to handle the network control commands come from userspace.
> >> Probably work for userspace driver but not kernel driver.
> > Exactly. This is only for userspace.
> >
> > I got your point now. In virtio-mdev kernel driver case,
> > the ctrl-vq can be special as well.
> >
> 
> Then maybe it's better to introduce vhost-mdev-net on top?
> 
> Looking at the other type of virtio device:
> 
> - console have two control virtqueues when multiqueue port is enabled
> 
> - SCSI has controlq + eventq
> 
> - GPU has controlq
> 
> - Crypto device has one controlq
> 
> - Socket has eventq
> 
> ...

Thanks for the list! It looks dirty to define specific
commands and types in vhost UAPI for each of them in the
future. It's definitely much better to find an approach
to solve it once for all if possible..

Just a quick thought, considering all vhost-mdev does
is just to forward settings between parent and userspace,
I'm wondering whether it's possible to make the argp
opaque in vhost-mdev UAPI and just introduce one generic
ioctl command to deliver these device specific commands
(which are opaque in vhost-mdev as vhost-mdev just pass
the pointer -- argp) defined by spec.

I'm also fine with exposing ctrlq to userspace directly.
PS. It's interesting that some devices have more than
one ctrlq. I need to take a close look first..


> 
> Thanks
> 

Re: [RFC] vhost_mdev: add network control vq support

[Jason Wang]

On 2019/10/30 下午7:54, Tiwei Bie wrote:
> On Wed, Oct 30, 2019 at 03:04:37PM +0800, Jason Wang wrote:
>> On 2019/10/30 下午2:17, Tiwei Bie wrote:
>>> On Tue, Oct 29, 2019 at 06:51:32PM +0800, Jason Wang wrote:
>>>> On 2019/10/29 下午6:17, Tiwei Bie wrote:
>>>>> This patch adds the network control vq support in vhost-mdev.
>>>>> A vhost-mdev specific op is introduced to allow parent drivers
>>>>> to handle the network control commands come from userspace.
>>>> Probably work for userspace driver but not kernel driver.
>>> Exactly. This is only for userspace.
>>>
>>> I got your point now. In virtio-mdev kernel driver case,
>>> the ctrl-vq can be special as well.
>>>
>> Then maybe it's better to introduce vhost-mdev-net on top?
>>
>> Looking at the other type of virtio device:
>>
>> - console have two control virtqueues when multiqueue port is enabled
>>
>> - SCSI has controlq + eventq
>>
>> - GPU has controlq
>>
>> - Crypto device has one controlq
>>
>> - Socket has eventq
>>
>> ...
> Thanks for the list! It looks dirty to define specific
> commands and types in vhost UAPI for each of them in the
> future. It's definitely much better to find an approach
> to solve it once for all if possible..
>
> Just a quick thought, considering all vhost-mdev does
> is just to forward settings between parent and userspace,
> I'm wondering whether it's possible to make the argp
> opaque in vhost-mdev UAPI and just introduce one generic
> ioctl command to deliver these device specific commands
> (which are opaque in vhost-mdev as vhost-mdev just pass
> the pointer -- argp) defined by spec.


It looks that using opaque pointer is probably not good for UAPI. And we 
need also invent API for eventq.


>
> I'm also fine with exposing ctrlq to userspace directly.
> PS. It's interesting that some devices have more than
> one ctrlq. I need to take a close look first..


Thanks.


>
>
>> Thanks
>>