Re: [PATCH v8 22/24] vfio: Add VFIO_DEVICE_AT[DE]TACH_IOMMUFD_PT

[Alex Williamson <alex.williamson@redhat.com>]

Nit, ATDETACH?  [AT|DE]TACH?

On Mon, 27 Mar 2023 02:40:45 -0700
Yi Liu <yi.l.liu@intel.com> wrote:

> This adds ioctl for userspace to attach device cdev fd to and detach
> from IOAS/hw_pagetable managed by iommufd.
> 
>     VFIO_DEVICE_ATTACH_IOMMUFD_PT: attach vfio device to IOAS, hw_pagetable
> 				   managed by iommufd. Attach can be
> 				   undo by VFIO_DEVICE_DETACH_IOMMUFD_PT
> 				   or device fd close.
>     VFIO_DEVICE_DETACH_IOMMUFD_PT: detach vfio device from the current attached
> 				   IOAS or hw_pagetable managed by iommufd.
> 
> Reviewed-by: Kevin Tian <kevin.tian@intel.com>
> Tested-by: Terrence Xu <terrence.xu@intel.com>
> Tested-by: Nicolin Chen <nicolinc@nvidia.com>
> Tested-by: Matthew Rosato <mjrosato@linux.ibm.com>
> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
> ---
>  drivers/vfio/device_cdev.c | 85 ++++++++++++++++++++++++++++++++++++++
>  drivers/vfio/vfio.h        | 16 +++++++
>  drivers/vfio/vfio_main.c   |  8 ++++
>  include/uapi/linux/vfio.h  | 52 +++++++++++++++++++++++
>  4 files changed, 161 insertions(+)
> 
> diff --git a/drivers/vfio/device_cdev.c b/drivers/vfio/device_cdev.c
> index 2b563bac50b9..b5de997bff6d 100644
> --- a/drivers/vfio/device_cdev.c
> +++ b/drivers/vfio/device_cdev.c
> @@ -197,6 +197,91 @@ long vfio_device_ioctl_bind_iommufd(struct vfio_device_file *df,
>  	return ret;
>  }
>  
> +int vfio_ioctl_device_attach(struct vfio_device_file *df,
> +			     struct vfio_device_attach_iommufd_pt __user *arg)
> +{
> +	struct vfio_device *device = df->device;
> +	struct vfio_device_attach_iommufd_pt attach;
> +	unsigned long minsz;
> +	int ret;
> +
> +	static_assert(__same_type(arg->pt_id, attach.pt_id));

Same comment as previous, given these are the same field of the same
structure, I don't understand how this could ever assert.

> +
> +	minsz = offsetofend(struct vfio_device_attach_iommufd_pt, pt_id);
> +
> +	if (copy_from_user(&attach, arg, minsz))
> +		return -EFAULT;
> +
> +	if (attach.argsz < minsz || attach.flags)
> +		return -EINVAL;
> +
> +	if (!device->ops->bind_iommufd)
> +		return -ENODEV;

Same as previous, we already require this to enable cdev support, so
this seems ultra paranoid.

> +
> +	/* ATTACH only allowed for cdev fds */
> +	if (df->group)
> +		return -EINVAL;
> +
> +	mutex_lock(&device->dev_set->lock);
> +	/* noiommufd mode doesn't allow attach */
> +	if (!df->iommufd) {
> +		ret = -EOPNOTSUPP;
> +		goto out_unlock;
> +	}
> +
> +	ret = device->ops->attach_ioas(device, &attach.pt_id);
> +	if (ret)
> +		goto out_unlock;
> +
> +	ret = copy_to_user(&arg->pt_id, &attach.pt_id,
> +			   sizeof(attach.pt_id)) ? -EFAULT : 0;
> +	if (ret)
> +		goto out_detach;
> +	mutex_unlock(&device->dev_set->lock);
> +
> +	return 0;
> +
> +out_detach:
> +	device->ops->detach_ioas(device);
> +out_unlock:
> +	mutex_unlock(&device->dev_set->lock);
> +	return ret;
> +}
> +
> +int vfio_ioctl_device_detach(struct vfio_device_file *df,
> +			     struct vfio_device_detach_iommufd_pt __user *arg)
> +{
> +	struct vfio_device *device = df->device;
> +	struct vfio_device_detach_iommufd_pt detach;
> +	unsigned long minsz;
> +
> +	minsz = offsetofend(struct vfio_device_detach_iommufd_pt, flags);
> +
> +	if (copy_from_user(&detach, arg, minsz))
> +		return -EFAULT;
> +
> +	if (detach.argsz < minsz || detach.flags)
> +		return -EINVAL;
> +
> +	if (!device->ops->bind_iommufd)
> +		return -ENODEV;
> +
> +	/* DETACH only allowed for cdev fds */
> +	if (df->group)
> +		return -EINVAL;
> +
> +	mutex_lock(&device->dev_set->lock);
> +	/* noiommufd mode doesn't support detach */
> +	if (!df->iommufd) {
> +		mutex_unlock(&device->dev_set->lock);
> +		return -EOPNOTSUPP;
> +	}
> +	device->ops->detach_ioas(device);
> +	mutex_unlock(&device->dev_set->lock);
> +
> +	return 0;
> +}

For both of these, can't a user trigger the
WARN_ON(!vdev->iommufd_device) if they call either of these before
VFIO_DEVICE_BIND_IOMMUFD?  Thanks,

Alex

> +
>  static char *vfio_device_devnode(const struct device *dev, umode_t *mode)
>  {
>  	return kasprintf(GFP_KERNEL, "vfio/devices/%s", dev_name(dev));
> diff --git a/drivers/vfio/vfio.h b/drivers/vfio/vfio.h
> index ace3d52b0928..c199e410db18 100644
> --- a/drivers/vfio/vfio.h
> +++ b/drivers/vfio/vfio.h
> @@ -284,6 +284,10 @@ int vfio_device_fops_cdev_open(struct inode *inode, struct file *filep);
>  void vfio_device_cdev_close(struct vfio_device_file *df);
>  long vfio_device_ioctl_bind_iommufd(struct vfio_device_file *df,
>  				    struct vfio_device_bind_iommufd __user *arg);
> +int vfio_ioctl_device_attach(struct vfio_device_file *df,
> +			     struct vfio_device_attach_iommufd_pt __user *arg);
> +int vfio_ioctl_device_detach(struct vfio_device_file *df,
> +			     struct vfio_device_detach_iommufd_pt __user *arg);
>  int vfio_cdev_init(struct class *device_class);
>  void vfio_cdev_cleanup(void);
>  #else
> @@ -317,6 +321,18 @@ static inline long vfio_device_ioctl_bind_iommufd(struct vfio_device_file *df,
>  	return -EOPNOTSUPP;
>  }
>  
> +static inline int vfio_ioctl_device_attach(struct vfio_device_file *df,
> +					   struct vfio_device_attach_iommufd_pt __user *arg)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
> +static inline int vfio_ioctl_device_detach(struct vfio_device_file *df,
> +					   struct vfio_device_detach_iommufd_pt __user *arg)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
>  static inline int vfio_cdev_init(struct class *device_class)
>  {
>  	return 0;
> diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
> index 375086c8803f..896d8bb49585 100644
> --- a/drivers/vfio/vfio_main.c
> +++ b/drivers/vfio/vfio_main.c
> @@ -1150,6 +1150,14 @@ static long vfio_device_fops_unl_ioctl(struct file *filep,
>  		ret = vfio_ioctl_device_feature(device, (void __user *)arg);
>  		break;
>  
> +	case VFIO_DEVICE_ATTACH_IOMMUFD_PT:
> +		ret = vfio_ioctl_device_attach(df, (void __user *)arg);
> +		break;
> +
> +	case VFIO_DEVICE_DETACH_IOMMUFD_PT:
> +		ret = vfio_ioctl_device_detach(df, (void __user *)arg);
> +		break;
> +
>  	default:
>  		if (unlikely(!device->ops->ioctl))
>  			ret = -EINVAL;
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 62b2f2497525..bf6c97e759c7 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -231,6 +231,58 @@ struct vfio_device_bind_iommufd {
>  
>  #define VFIO_DEVICE_BIND_IOMMUFD	_IO(VFIO_TYPE, VFIO_BASE + 19)
>  
> +/*
> + * VFIO_DEVICE_ATTACH_IOMMUFD_PT - _IOW(VFIO_TYPE, VFIO_BASE + 20,
> + *					struct vfio_device_attach_iommufd_pt)
> + *
> + * Attach a vfio device to an iommufd address space specified by IOAS
> + * id or hw_pagetable (hwpt) id.
> + *
> + * Available only after a device has been bound to iommufd via
> + * VFIO_DEVICE_BIND_IOMMUFD
> + *
> + * Undo by VFIO_DEVICE_DETACH_IOMMUFD_PT or device fd close.
> + *
> + * @argsz:	user filled size of this data.
> + * @flags:	must be 0.
> + * @pt_id:	Input the target id which can represent an ioas or a hwpt
> + *		allocated via iommufd subsystem.
> + *		Output the attached hwpt id which could be the specified
> + *		hwpt itself or a hwpt automatically created for the
> + *		specified ioas by kernel during the attachment.
> + *
> + * Return: 0 on success, -errno on failure.
> + */
> +struct vfio_device_attach_iommufd_pt {
> +	__u32	argsz;
> +	__u32	flags;
> +	__u32	pt_id;
> +};
> +
> +#define VFIO_DEVICE_ATTACH_IOMMUFD_PT		_IO(VFIO_TYPE, VFIO_BASE + 20)
> +
> +/*
> + * VFIO_DEVICE_DETACH_IOMMUFD_PT - _IOW(VFIO_TYPE, VFIO_BASE + 21,
> + *					struct vfio_device_detach_iommufd_pt)
> + *
> + * Detach a vfio device from the iommufd address space it has been
> + * attached to. After it, device should be in a blocking DMA state.
> + *
> + * Available only after a device has been bound to iommufd via
> + * VFIO_DEVICE_BIND_IOMMUFD.
> + *
> + * @argsz:	user filled size of this data.
> + * @flags:	must be 0.
> + *
> + * Return: 0 on success, -errno on failure.
> + */
> +struct vfio_device_detach_iommufd_pt {
> +	__u32	argsz;
> +	__u32	flags;
> +};
> +
> +#define VFIO_DEVICE_DETACH_IOMMUFD_PT		_IO(VFIO_TYPE, VFIO_BASE + 21)
> +
>  /**
>   * VFIO_DEVICE_GET_INFO - _IOR(VFIO_TYPE, VFIO_BASE + 7,
>   *						struct vfio_device_info)