Re: [PATCH v4 5/9] vfio: Mark cdev usage in vfio_device

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

On Wed, 26 Apr 2023 07:54:15 -0700
Yi Liu <yi.l.liu@intel.com> wrote:

> Use it to differentiate whether to report group_id or dev_id in revised
> VFIO_DEVICE_GET_PCI_HOT_RESET_INFO ioctl. Though it is not set at this
> moment introducing it now allows us to get hot reset ready for cdev.
> 
> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
> ---
>  include/linux/vfio.h | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> index 4ee613924435..298f4ef16be7 100644
> --- a/include/linux/vfio.h
> +++ b/include/linux/vfio.h
> @@ -63,6 +63,7 @@ struct vfio_device {
>  	bool iommufd_attached;
>  #endif
>  	bool noiommu;
> +	bool cdev_opened;
>  };
>  
>  /**
> @@ -140,6 +141,12 @@ int vfio_iommufd_emulated_attach_ioas(struct vfio_device *vdev, u32 *pt_id);
>  	((int (*)(struct vfio_device *vdev, u32 *pt_id)) NULL)
>  #endif
>  
> +static inline bool vfio_device_cdev_opened(struct vfio_device *device)
> +{
> +	lockdep_assert_held(&device->dev_set->lock);
> +	return device->cdev_opened;
> +}

The lockdep test doesn't make much sense here, the method of opening
the device can't change from an ioctl called on the device, which is
the only path using this.  If there needs to be a placeholder for
future code, it should probably statically return false here and we can
save adding the structure field and locking checks based on the
semantics of how the field is actually used later.  Thanks,

Alex