[dpdk-dev] [RFC] Enable primary/secondary model for vdev

[Tan, Jianfeng]

Any comments please?

> -----Original Message-----
> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Tan, Jianfeng
> Sent: Thursday, May 11, 2017 2:20 PM
> To: dev at dpdk.org
> Cc: Thomas Monjalon; Richardson, Bruce; Ananyev, Konstantin; Stephen
> Hemminger; Yuanhan Liu; Yigit, Ferruh; Yang, Zhiyong;
> huanghuai at meituan.com
> Subject: [dpdk-dev] [RFC] Enable primary/secondary model for vdev
> 
> Hi,
> 
> Status quo:
> Almost none of vdev supports primary/secondary model. Two exceptions
> are
> rte_ring, virtio-user (limited support). Two problems facing this issue.
> 
> P1: How to attach vdev in secondary process?
> 
> Previous discussion: http://dpdk.org/ml/archives/dev/2017-
> April/063370.html
> According current implementation, vdev can be recognized on vdev bus
> only if it is explicitly assigned in the parameters, or invokes call
> rte_eal_vdev_init() to create one. Assigning --vdev parameter explicitly
> on secondary process is not the optimal way. Instead, we can iterate
> rte_eth_dev_data array to discover/obtain all devices, which seems a
> more unified solution with PCI devices.
> 
> If we only need to obtain the statistics of vdev in secondary process
> (like what dpdk-procinfo does), solving above issue is enough, but if we
> need to Rx/Tx packets in secondary process for vdev, we need to solve
> the following problem too.
> 
> P2: How to share dev-specific FDs to secondary process?
> 
> We need to share the FDs which are opened at primary process, for
> example, the socket file of pcap, the char device of tap, the QEMU
> memory region fds of vhost-user, etc. The only (as far as we know) way
> to share FD between processes in Linux is to use ancillary data of
> sendmsg/recvmsg on unix socket. That means we propose a new socket file
> created for each primary proess, and secondary processes will connect
> with this unix socket; and for simplicity, we also propose a new API to
> share FD, so that vdev can make use of it to share FDs.
> 
> Another problem I'd like to make clear is: can secondary processes own
> ports that does not belong to primary?
> 
> Besides, there are two errors in documents: (1) rte_ring supports
> primary/secondary model but the document does not state that; (2) pcap
> does not support primary/secondary model but the document states it
> supports.
> 
> Thanks,
> Jianfeng