Re: [dpdk-dev] [PATCH v2 1/2] vhost: support inflight share memory protocol feature

["Yu, Jin" <jin.yu@intel.com>]

Hi Tiwei， thanks.

> -----Original Message-----
> From: Bie, Tiwei
> Sent: Wednesday, July 10, 2019 3:18 PM
> To: Yu, Jin <jin.yu@intel.com>
> Cc: dev@dpdk.org; Liu, Changpeng <changpeng.liu@intel.com>;
> maxime.coquelin@redhat.com; Wang, Zhihong <zhihong.wang@intel.com>;
> LinLi <lilin24@baidu.com>; XunNi <nixun@baidu.com>; YuZhang
> <zhangyu31@baidu.com>
> Subject: Re: [PATCH v2 1/2] vhost: support inflight share memory protocol
> feature
> 
> On Wed, Jul 10, 2019 at 06:43:55PM +0800, JinYu wrote:
> > This patch introduces two new messages VHOST_USER_GET_INFLIGHT_FD
> and
> > VHOST_USER_SET_INFLIGHT_FD to support transferring a shared buffer
> > between qemu and backend.
> >
> > Firstly, qemu uses VHOST_USER_GET_INFLIGHT_FD to get the shared buffer
> > from backend. Then qemu should send it back through
> > VHOST_USER_SET_INFLIGHT_FD each time we start vhost-user.
> >
> > This shared buffer is used to process inflight I/O when backend
> > reconnect.
> 
> I saw you send several patch sets for v2. It's a bit confusing. Please bump the
> version when you send a new series. Besides, please keep the cover letter.
Sorry for the confusion. There are some misoperations and I have set them superseded.
> 
> >
> > Signed-off-by: LinLi <lilin24@baidu.com>
> > Signed-off-by: XunNi <nixun@baidu.com>
> > Signed-off-by: YuZhang <zhangyu31@baidu.com>
> > Signed-off-by: JinYu <jin.yu@intel.com>
> 
> There should be a space between FirstName and LastName.
Got it.
> 
> [...]
> >
> > +struct inflight_desc_split {
> > +	uint8_t		inflight;
> > +	uint8_t		padding[5];
> > +	uint16_t	next;
> > +	uint64_t	counter;
> > +};
> > +
> > +struct inflight_info_split {
> > +	uint64_t		features;
> > +	uint16_t		version;
> > +	uint16_t		desc_num;
> > +	uint16_t		last_inflight_io;
> > +	uint16_t		used_idx;
> > +	struct inflight_desc_split desc[0];
> > +};
> 
> I haven't looked into the details yet. Is it necessary to expose above
> definitions to applications? It seems they are not used in your example code.
Will revise in the next version.
> 
> > +
> > +struct resubmit_desc {
> > +	uint16_t index;
> > +	uint64_t counter;
> > +};
> > +
> > +struct resubmit_info {
> > +	struct resubmit_desc	*resubmit_list;
> > +	uint16_t		resubmit_num;
> > +};
> 
> The rte_vhost_ prefix is needed for vhost APIs.
> 
> > +
> > +struct rte_vhost_ring_inflight_split {
> > +	union {
> > +		struct inflight_info_split *inflight_split;
> > +		/* TODO */
> > +	};
> 
> Ditto. Seems it's not used in example code.
> 
> > +
> > +	struct resubmit_info *resubmit_inflight_split; };
> > +
> >  struct rte_vhost_vring {
> >  	struct vring_desc	*desc;
> >  	struct vring_avail	*avail;
> > @@ -603,6 +642,22 @@ uint16_t rte_vhost_dequeue_burst(int vid,
> uint16_t queue_id,
> >   */
> >  int rte_vhost_get_mem_table(int vid, struct rte_vhost_memory **mem);
> >
> > +/**
> > + * Get guest inflight vring info, including inflight ring and resubmit list.
> > + *
> > + * @param vid
> > + *  vhost device ID
> > + * @param vring_idx
> > + *  vring index
> > + * @param vring
> > + *  the structure to hold the requested inflight vring info
> > + * @return
> > + *  0 on success, -1 on failure
> > + */
> > +int __rte_experimental
> > +rte_vhost_get_vhost_ring_inflight_split(int vid, uint16_t vring_idx,
> > +			      struct rte_vhost_ring_inflight_split *vring);
> > +
> >  /**
> >   * Get guest vring info, including the vring address, vring size, etc.
> >   *
> > @@ -631,6 +686,56 @@ int rte_vhost_get_vhost_vring(int vid, uint16_t
> vring_idx,
> >   */
> >  int rte_vhost_vring_call(int vid, uint16_t vring_idx);
> >
> > +/**
> > + * set inflight flag for a desc.
> > + *
> > + * @param vid
> > + *  vhost device ID
> > + * @param vring_idx
> > + *  vring index
> > + * @param idx
> > + *  inflight entry index
> > + * @return
> > + *  0 on success, -1 on failure
> > + */
> > +int __rte_experimental
> > +rte_vhost_set_inflight_desc_split(int vid, uint16_t vring_idx,
> > +		uint16_t idx);
> [...]
> > +int __rte_experimental
> > +rte_vhost_clr_inflight_desc_split(int vid, uint16_t vring_idx,
> > +		uint16_t last_used_idx, uint16_t idx);
> [...]
> > +int __rte_experimental
> > +rte_vhost_set_last_inflight_io_split(int vid, uint16_t vring_idx,
> > +		uint16_t idx);
> 
> What will be different in the function prototype when we design above three
> APIs for packed ring?
The whole process is quite different as there are no avail ring and userd ring.