Subject: Re: [PATCH net-next v2 1/5] virtio: add packed ring definitions

From: "Michael S. Tsirkin" <[email-masked]>
Date: Fri, 7 Sep 2018 09:51:23 -0400

On Wed, Jul 11, 2018 at 10:27:07AM +0800, Tiwei Bie wrote:
> Signed-off-by: Tiwei Bie <[email-masked]>
> ---
>  include/uapi/linux/virtio_config.h |  3 +++
>  include/uapi/linux/virtio_ring.h   | 43 ++++++++++++++++++++++++++++++
>  2 files changed, 46 insertions(+)
> 
> diff --git a/include/uapi/linux/virtio_config.h b/include/uapi/linux/virtio_config.h
> index 449132c76b1c..1196e1c1d4f6 100644
> --- a/include/uapi/linux/virtio_config.h
> +++ b/include/uapi/linux/virtio_config.h
> @@ -75,6 +75,9 @@
>   */
>  #define VIRTIO_F_IOMMU_PLATFORM		33
>  
> +/* This feature indicates support for the packed virtqueue layout. */
> +#define VIRTIO_F_RING_PACKED		34
> +
>  /*
>   * Does the device support Single Root I/O Virtualization?
>   */
> diff --git a/include/uapi/linux/virtio_ring.h b/include/uapi/linux/virtio_ring.h
> index 6d5d5faa989b..0254a2ba29cf 100644
> --- a/include/uapi/linux/virtio_ring.h
> +++ b/include/uapi/linux/virtio_ring.h
> @@ -44,6 +44,10 @@
>  /* This means the buffer contains a list of buffer descriptors. */
>  #define VRING_DESC_F_INDIRECT	4
>  
> +/* Mark a descriptor as available or used. */
> +#define VRING_DESC_F_AVAIL	(1ul << 7)
> +#define VRING_DESC_F_USED	(1ul << 15)
> +
>  /* The Host uses this in used->flags to advise the Guest: don't kick me when
>   * you add a buffer.  It's unreliable, so it's simply an optimization.  Guest
>   * will still kick if it's out of buffers. */
> @@ -53,6 +57,17 @@
>   * optimization.  */
>  #define VRING_AVAIL_F_NO_INTERRUPT	1
>  
> +/* Enable events. */
> +#define VRING_EVENT_F_ENABLE	0x0
> +/* Disable events. */
> +#define VRING_EVENT_F_DISABLE	0x1
> +/*
> + * Enable events for a specific descriptor
> + * (as specified by Descriptor Ring Change Event Offset/Wrap Counter).
> + * Only valid if VIRTIO_RING_F_EVENT_IDX has been negotiated.
> + */
> +#define VRING_EVENT_F_DESC	0x2
> +
>  /* We support indirect buffer descriptors */
>  #define VIRTIO_RING_F_INDIRECT_DESC	28
>  

These are for the packed ring, right? Pls prefix accordingly.
Also, you likely need macros for the wrap counters.

> @@ -171,4 +186,32 @@ static inline int vring_need_event(__u16 event_idx, __u16 new_idx, __u16 old)
>  	return (__u16)(new_idx - event_idx - 1) < (__u16)(new_idx - old);
>  }
>  
> +struct vring_packed_desc_event {
> +	/* Descriptor Ring Change Event Offset/Wrap Counter. */
> +	__virtio16 off_wrap;
> +	/* Descriptor Ring Change Event Flags. */
> +	__virtio16 flags;
> +};
> +
> +struct vring_packed_desc {
> +	/* Buffer Address. */
> +	__virtio64 addr;
> +	/* Buffer Length. */
> +	__virtio32 len;
> +	/* Buffer ID. */
> +	__virtio16 id;
> +	/* The flags depending on descriptor type. */
> +	__virtio16 flags;
> +};

Don't use __virtioXX types, just __leXX ones.

> +
> +struct vring_packed {
> +	unsigned int num;
> +
> +	struct vring_packed_desc *desc;
> +
> +	struct vring_packed_desc_event *driver;
> +
> +	struct vring_packed_desc_event *device;
> +};
> +
>  #endif /* _UAPI_LINUX_VIRTIO_RING_H */
> -- 
> 2.18.0