# Re: \[PATCH V2 RESEND 2/4\] virtio-pci library: introduce vp\_modern\_get\_driver\_features()

- From: Eli Cohen \<hidden\>
- Date: 2021-06-02 07:46:21 
- List: netdev
- Page: https://ratatoskr.run/netdev/2021/06/1399442
- Thread: https://ratatoskr.run/kvm/2021/06/1399202/t.md

```text
On Wed, Jun 02, 2021 at 10:15:34AM +0800, Jason Wang wrote:
> This patch introduce a helper to get driver/guest features from the
> device.
> 
> Signed-off-by: Jason Wang <redacted>
Reviewed-by: Eli Cohen <redacted>
> ---
>  drivers/virtio/virtio_pci_modern_dev.c | 21 +++++++++++++++++++++
>  include/linux/virtio_pci_modern.h      |  1 +
>  2 files changed, 22 insertions(+)
> 
> diff --git a/drivers/virtio/virtio_pci_modern_dev.c b/drivers/virtio/virtio_pci_modern_dev.c
> index 54f297028586..e11ed748e661 100644
> --- a/drivers/virtio/virtio_pci_modern_dev.c
> +++ b/drivers/virtio/virtio_pci_modern_dev.c
> @@ -383,6 +383,27 @@ u64 vp_modern_get_features(struct virtio_pci_modern_device *mdev)
>  }
>  EXPORT_SYMBOL_GPL(vp_modern_get_features);
>  
> +/*
> + * vp_modern_get_driver_features - get driver features from device
> + * @mdev: the modern virtio-pci device
> + *
> + * Returns the driver features read from the device
> + */
> +u64 vp_modern_get_driver_features(struct virtio_pci_modern_device *mdev)
> +{
> +	struct virtio_pci_common_cfg __iomem *cfg = mdev->common;
> +
> +	u64 features;
> +
> +	vp_iowrite32(0, &cfg->guest_feature_select);
> +	features = vp_ioread32(&cfg->guest_feature);
> +	vp_iowrite32(1, &cfg->guest_feature_select);
> +	features |= ((u64)vp_ioread32(&cfg->guest_feature) << 32);
> +
> +	return features;
> +}
> +EXPORT_SYMBOL_GPL(vp_modern_get_driver_features);
> +
>  /*
>   * vp_modern_set_features - set features to device
>   * @mdev: the modern virtio-pci device
> diff --git a/include/linux/virtio_pci_modern.h b/include/linux/virtio_pci_modern.h
> index 6a95b58fd0f4..eb2bd9b4077d 100644
> --- a/include/linux/virtio_pci_modern.h
> +++ b/include/linux/virtio_pci_modern.h
> @@ -79,6 +79,7 @@ static inline void vp_iowrite64_twopart(u64 val,
>  }
>  
>  u64 vp_modern_get_features(struct virtio_pci_modern_device *mdev);
> +u64 vp_modern_get_driver_features(struct virtio_pci_modern_device *mdev);
>  void vp_modern_set_features(struct virtio_pci_modern_device *mdev,
>  		     u64 features);
>  u32 vp_modern_generation(struct virtio_pci_modern_device *mdev);
> -- 
> 2.25.1
> 
```