Re: [PATCH net-next v3 01/13] virtio: add packed ring types and macros

[Jason Wang <jasowang@redhat.com>]

On 2018/11/21 下午6:03, Tiwei Bie wrote:
> Add types and macros for packed ring.
>
> Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
> ---
>   include/uapi/linux/virtio_config.h |  3 +++
>   include/uapi/linux/virtio_ring.h   | 52 ++++++++++++++++++++++++++++++++++++++
>   2 files changed, 55 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..2414f8af26b3 100644
> --- a/include/uapi/linux/virtio_ring.h
> +++ b/include/uapi/linux/virtio_ring.h
> @@ -44,6 +44,13 @@
>   /* This means the buffer contains a list of buffer descriptors. */
>   #define VRING_DESC_F_INDIRECT	4
>   
> +/*
> + * Mark a descriptor as available or used in packed ring.
> + * Notice: they are defined as shifts instead of shifted values.


This looks inconsistent to previous flags, any reason for using shifts?


> + */
> +#define VRING_PACKED_DESC_F_AVAIL	7
> +#define VRING_PACKED_DESC_F_USED	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 +60,23 @@
>    * optimization.  */
>   #define VRING_AVAIL_F_NO_INTERRUPT	1
>   
> +/* Enable events in packed ring. */
> +#define VRING_PACKED_EVENT_FLAG_ENABLE	0x0
> +/* Disable events in packed ring. */
> +#define VRING_PACKED_EVENT_FLAG_DISABLE	0x1
> +/*
> + * Enable events for a specific descriptor in packed ring.
> + * (as specified by Descriptor Ring Change Event Offset/Wrap Counter).
> + * Only valid if VIRTIO_RING_F_EVENT_IDX has been negotiated.
> + */
> +#define VRING_PACKED_EVENT_FLAG_DESC	0x2


Any reason for using _FLAG_ instead of _F_?

Thanks


> +
> +/*
> + * Wrap counter bit shift in event suppression structure
> + * of packed ring.
> + */
> +#define VRING_PACKED_EVENT_F_WRAP_CTR	15
> +
>   /* We support indirect buffer descriptors */
>   #define VIRTIO_RING_F_INDIRECT_DESC	28
>   
> @@ -171,4 +195,32 @@ 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. */
> +	__le16 off_wrap;
> +	/* Descriptor Ring Change Event Flags. */
> +	__le16 flags;
> +};
> +
> +struct vring_packed_desc {
> +	/* Buffer Address. */
> +	__le64 addr;
> +	/* Buffer Length. */
> +	__le32 len;
> +	/* Buffer ID. */
> +	__le16 id;
> +	/* The flags depending on descriptor type. */
> +	__le16 flags;
> +};
> +
> +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 */