OVS DPDK vhost-user详解（十三）
vhost user协议的控制和数据通道
所有的控制信息通过UNIX套接口（控制通道）交互。包括为进行直接内存访问而交换的内存映射信息，以及当数据填入virtio队列后需要出发的kick事件和中断信息。在Neutron中此UNIX套接口命名为vhuxxxxxxxx-xx；
数据通道事实上由内存直接访问实现。客户机中的virtio-net驱动分配一部分内存用于virtio的队列。virtio标准定义了此队列的结构。QEMU通过控制通道将此部分内存的地址共享给OVS DPDK。DPDK自身映射一个相同标准的virtio队列结构到此内存上，藉此来读写客户机巨页内存中的virtio队列。直接内存访问的实现需要在OVS DPDK和QEMU之间使用巨页内存。如果QEMU设置正确，但是没有配置巨页内存，OVS DPDK将不能访问QEMU的内存，二者也就不能交换数据报文。如果用户忘记了请求客户机巨页内存，nova将通过宏数据通知用户。
当OVS DPDK向客户机发送数据包时，这些数据包在OVS DPDK的统计里面显示为接口vhuxxxxxxxx-xx的发送Tx流量。在客户机中，显示为接收Rx流量。
当客户机向OVS DPDK发送数据包时，这些数据包在客户机中显示为发送Tx流量，而在OVS DPDK中显示为接口vhuxxxxxxxx-xx的接收Rx流量。
客户机并没有硬件的统计计数。ethtool工具的-s选项未实现。所有的底层统计计数只能使用OVS的命令显示（ovs-vsctl list get interfave vhuxxxxxxxx-xx statistics），因此显示的数据都是基于OVS DPDK的视角。
虽然数据包可通过共享内存传输，但是还需要一种方法告知对端数据包已经拷贝到virtio队列中。通过vhost user套接口vhuxxxxxxxx-xx实现的控制通道可用来完成通知（kicking）对方的功能。通知必然有代价。首先，需要一个写套接口的系统调用；之后对端需要处理一个中断操作。所以，接收双方都会在控制通道上消耗时间。
为避免控制通道的通知消耗，OpenvSwitch和QEMU都可以设置特殊标志以告知对方其不愿接收中断。尽管如此，只有在采用临时或者固定查询virtio队列方式时才能使用不接收中断的功能。
为客户机的性能考虑其本身可采用DPDK处理数据包。尽管Linux内核采用轮询处理和中断相结合的NAPI机制，但是产生的中断数量仍然很多。OVS DPDK以非常高的速率发送数据包到客户机。同时，QEMU的virtio队列的收发缓存数被限制在了默认的256与最大1024之间。结果，客户机必须以非常快的速度处理数据包。理想的实现就是使用DPDK的PMD驱动不停的轮询客户机端口进行数据包处理。
vhost user协议标准
Vhost-user协议
Copyright (c) 2014 Virtual Open Systems Sarl.
This work is licensed under the terms of the GNU GPL, version 2 or later.
See the COPYING file in the top-level directory.
此协议旨在补充实现在Linux内核中的vhost的ioctl接口。
实现了与同一宿主机中的用户进程交互建立virtqueue队列的控制平面。通过UNIX套接口消息中的附加数据字段来共享文件描述符。
协议定义了通信的两端：主和从。主时要共享其virtqueues队列的进程，即QEMU。从为virtqueues队列的消费者。
当前实现中QEMU作为主，从为运行在用户空间的软件交换机，如Snabbswitch。
主和从在通信时都可以作为客户端（主动连接）或者服务端（监听）。
vhost user协议由两方组成：
- 主方 - QEMU
- 从方 - Open vSwitch或者其它软件交换机
vhost user各方都可运行在2种模式下：
- vhostuser-client - QEMU作为服务端，软件交换机作为客户端
- vhostuser - 软件交换机作为服务端，QEMU作为客户端。
vhost user实现基于内核的vhost架构，将所有特性实现在用户空间。
当QEMU客户机启动时，它将所有的客户机内存分配为共享的巨页内存。其操作系统的半虚拟化驱动virtio将保留这些巨页内存的一部分用作virtio环形缓存。这样OVS DPDK将可以直接读写客户机的virtio环形缓存。OVS DPDK和QEMU可通过此保留的内存空间交换网络数据包。
用户空间进程接收到客户机预先分配的共享内存文件描述符后，可直接存取与之关联的客户机内存空间中的vrings环结构。(http://www.virtualopensystems.com/en/solutions/guides/snabbswitch-qemu/).
参见以下的VM虚拟机，模式为vhostuser：
$ /usr/libexec/qemu-kvm
-name guest=instance-00000028,debug-threads=on-S
-object secret,id=masterKey0,format=raw,file=/var/lib/libvirt/qemu/domain-58-instance-00000028/master-key.aes-machine pc-i440fx-rhel7.4.0,accel=kvm,usb=off,dump-guest-core=off
-cpu Skylake-Client,ss=on,hypervisor=on,tsc_adjust=on,pdpe1gb=on,mpx=off,xsavec=off,xgetbv1=off-m 2048
-realtime mlock=off
-smp 8,sockets=4,cores=1,threads=2
-object memory-backend-file,id=ram-node0,prealloc=yes,mem-path=/dev/hugepages/libvirt/qemu/58-instance-00000028,share=yes,size=1073741824,host-nodes=0,policy=bind-numa node,nodeid=0,cpus=0-3,memdev=ram-node0
-object memory-backend-file,id=ram-node1,prealloc=yes,mem-path=/dev/hugepages/libvirt/qemu/58-instance-00000028,share=yes,size=1073741824,host-nodes=1,policy=bind-numa node,nodeid=1,cpus=4-7,memdev=ram-node1
-uuid 48888226-7b6b-415c-bcf7-b278ba0bca62 -smbios type=1,manufacturer=Red Hat,product=OpenStack Compute,version=14.1.0-3.el7ost,serial=3d5e138a-8193-41e4-ac95-de9bfc1a3ef1,uuid=48888226-7b6b-415c-bcf7-b278ba0bca62,family=Virtual Machine
-no-user-config
-nodefaults
-chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/domain-58-instance-00000028/monitor.sock,server,nowait-mon chardev=charmonitor,id=monitor,mode=control
-rtc base=utc,driftfix=slew
-global kvm-pit.lost_tick_policy=delay
-no-hpet
-no-shutdown
-boot strict=on
-device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2
-drive file=/var/lib/nova/instances/48888226-7b6b-415c-bcf7-b278ba0bca62/disk,format=qcow2,if=none,id=drive-virtio-disk0,cache=none
-device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x4,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1
-chardev socket,id=charnet0,path=/var/run/openvswitch/vhuc26fd3c6-4b
-netdev vhost-user,chardev=charnet0,queues=8,id=hostnet0
-device virtio-net-pci,mq=on,vectors=18,netdev=hostnet0,id=net0,mac=fa:16:3e:52:30:73,bus=pci.0,addr=0x3
-add-fd set=0,fd=33 -chardev file,id=charserial0,path=/dev/fdset/0,append=on
-device isa-serial,chardev=charserial0,id=serial0 -chardev pty,id=charserial1
-device isa-serial,chardev=charserial1,id=serial1
-device usb-tablet,id=input0,bus=usb.0,port=1
-vnc 172.16.2.10:1 -k en-us
-device cirrus-vga,id=video0,bus=pci.0,addr=0x2
-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x5
-msg timestamp=on
指定QEMU从巨页池中分配内存，并设置为共享内存。
-object memory-backend-file,id=ram-node0,prealloc=yes,mem-path=/dev/hugepages/libvirt/qemu/58-instance-00000028,share=yes,size=1073741824,host-nodes=0,policy=bind
-numa node,nodeid=0,cpus=0-3,memdev=ram-node0
-object memory-backend-file,id=ram-node1,prealloc=yes,mem-path=/dev/hugepages/libvirt/qemu/58-instance-00000028,share=yes,size=1073741824,host-nodes=1,policy=bind
尽管如此，简单的拷贝数据包到对方的缓存中还不足够。另外，vhost user协议使用一个UNIX套接口（vhu[a-f0-9-]）处理vswitch和QEMU之间的通信，包括在初始化过程中，和数据包拷贝到共享内存的virtio环中需要通知对方时。所以两者的交互包括基于控制通道（vhu）的创建操作和通知机制，与拷贝数据包的数据通道（直接内存访问）。
所述virtio机制要能工作，我们需要建立一个接口来初始化共享内存区域和交换event事件描述符。UNIX套接口提供的API接口可实现此要求。此套接口可用于初始化用户空间virtio传输（vhost-user），特别是：
- 初始化时确定Vrings，并且放入两个进程间的共享内存中；
- 使用eventfd映射到Vring事件。这样就可与QEMU/KVM中的实现相兼容，KVM可以关联客户机系统中virtio_pci驱动所触发事件与宿主机的eventfd（ioventfd和irqfd）文件描述符。
在两个进程间共享文件描述符与在一个进程和内核直接不相同。前者需要在UNIX套接口的sendmsg系统调用中设置SCM_RIGHTS标志。
vhostuser模式下，OVS创建vhu套接口，QEMU主动进行连接。vhostuser client模式下，QEMU创建vhu套接口，OVS进行连接。
在上面创建的vhostuser模式客户机实例中，指示QEMU连接一个类型为vhost-user的netdev到套接口/var/run/openvswitch/vhuc26fd3c6-4b:
-chardev socket,id=charnet0,path=/var/run/openvswitch/vhuc26fd3c6-4b \
-netdev vhost-user,chardev=charnet0,queues=8,id=hostnet0 \
-device virtio-net-pci,mq=on,vectors=18, \
netdev=hostnet0,id=net0,mac=fa:16:3e:52:30:73,bus=pci.0,addr=0x3
使用lsof命令显示此套接口为OVS所创建：
[root@overcloud-0 ~]# lsof -nn | grep vhuc26fd3c6-4b | awk '{print $1}' | uniq
当一方拷贝一个数据报文到共享内存的virtio环中时，另一方有两种选择：
- 类似(e.g. Linux kernel’s NAPI)或者 (e.g. DPDK’s PMD)的轮询队列，不需要通知就可取得新的数据报文；
- 非队列轮询，必须得到新报文到达的通知。
针对第二种情况，可通过独立的vhu套接口控制通道发送通知到客户机。通过交换eventfd文件描述符数据，控制通道可在用户空间实现中断。套接口的写操作要求系统调用，必将引起PMDs花费时间在内核空间。客户机可通过设置VRING_AVAIL_F_NO_INTERRUPT标志关闭控制通道中断通知。否则，当Open vSwitch网virtio环中填入新数据包时，将发送中断通知到客户机。
详情可参加此博客文章：http://blog.vmsplice.net/2011/09/qemu-internals-vhost-architecture.html
用户空间的vhost接口
vhost架构的一个惊人的特性是其并没有绑定在KVM上。其仅是一个用户空间接口并不依赖于KVM内核模块。这意味着其它的用户空间程序，比如libpcap，如果要获得高性能I/O接口，理论上也可以使用vhost设备。
当客户机通知宿主机其已在virtqueue中填入了数据时，需要通知vhost的工作进程有数据要进行处理（对于内核的virtio-net驱动，vhost工作进程为一个内核线程，名称为vhost-$pid，其中pid为QEMU的进程号）。既然vhost不依赖于KVM内核模块，二者就不能直接通信。所以vhost实例创建了一个eventfd文件描述符，提供给vhost工作进程去监听。KVM内核模块的ioeventfd特性可将一个eventfd文件描述符关联到一个特殊的客户机I/O操作上。QEMU用户空间在硬件寄存器VIRTIO_PCI_QUEUE_NOTIFY的I/O访问上注册了virtqueue的通知ioeventfd。当客户机写VIRTIO_PCI_QUEUE_NOTIFY寄存器时将会发送virtqueue队列通知，vhost工作进程将接收到KVM内核模块通过ioeventfd发来的通知。
在vhost工作进程需要发送中断到客户机的反向路径上使用相同的方式。vhost通过写一个“call”文件描述符去通知客户机。KVM内核模块的另一个特性irqfd中断描述符可使eventfd出发客户机中断。QEMU用户空间为virtio的PCI设备中断注册了一个irqfd文件描述符，并将此irqfd交于vhost实例。vhost工作进程即可通过此“call”文件描述符去中断客户机。
最终，vhost实例仅了解到客户机的内存映射、kick通知eventfd文件描述符和call中断文件描述符。
更多细节，参考Linux内核中内核相关代码：
drivers/vhost/vhost.c - 通用vhost驱动代码
drivers/vhost/net.c - vhost-net网络设备驱动代码
virt/kvm/eventfd.c - ioeventfd事件和irqfd中断文件描述符实现
QEMU初始化vhost实例的用户空间代码：
hw/vhost.c - 通用vhost初始化代码
hw/vhost_net.c - vhost-net网络设备初始化代码
数据通道-直接内存访问
virtqueue的内存映射
virtio官方标准定义了virtqueue的结构。
virtqueues
2.4 Virtqueues
virtio设备的大数据传输机制命名为virtqueue虚拟队列。每个设备可以有多个virtqueues，也可以没有
virtqueue队列。16位的队列大小参数指定了队列内成员的数量，也限定了队列的总大小。
每个virtqueue队列有三个部分组成：
Descriptor Table - 描述符表
Available Ring - 可用环
Used Ring - 已用环
virtio标志精确的定义了描述符表、可用环和已用环的结构。例如，可用环的定义：
http://docs.oasis-open.org/virtio/virtio/v1.0/virtio-v1.0.html
virtq_avail
2.4.6 virtqueue可用环结构
struct virtq_avail {
#define VIRTQ_AVAIL_F_NO_INTERRUPT 1
le16 flags;
le16 idx;
le16 ring[ /* Queue Size */ ];
le16 used_event; /* Only if VIRTIO_F_EVENT_IDX */
};
驱动程序使用可用环提供发送缓存给设备。其中每个环项指向一个描述符链的开头。可用环只能由驱动程序写，由设备读。
idx成员指示驱动程序将下一个描述符入口项放在了ring成员的哪个位置（不超过队列长度）。其从0开始增加。
传统的标准[Virtio PCI Draft]将此结构定义为vring_avail，将宏定义命名为
VRING_AVAIL_F_NO_INTERRUPT，但是本质结构都还是相同的。
DPDK的virtio标准实现代码，其也是使用传统virtio标准中的结构定义：
dpdk-18.08/drivers/net/virtio/virtio_ring.h
vring、vring_desc、vring_avail、vring_used
/* VirtIO ring descriptors: 16 bytes.
* These can chain together via "next".
*/
struct vring_desc {
uint64_t addr; /* Address (guest-physical). */
uint32_t len; /* Length. */
uint16_t flags; /* The flags as indicated above. */
uint16_t next; /* We chain unused descriptors via this. */
};
struct vring_avail {
uint16_t flags;
uint16_t idx;
uint16_t ring[0];
};
/* id is a 16bit index. uint32_t is used here for ids for padding reasons. */
struct vring_used_elem {
/* Index of start of used descriptor chain. */
uint32_t id;
/* Total length of the descriptor chain which was written to. */
uint32_t len;
};
struct vring_used {
uint16_t flags;
volatile uint16_t idx;
struct vring_used_elem ring[0];
};
struct vring {
unsigned int num;
struct vring_desc *desc;
struct vring_avail *avail;
struct vring_used *used;
};
dpdk-18.08/lib/librte_vhost/vhost.h
vhost_virtqueue
/**
* Structure contains variables relevant to RX/TX virtqueues.
*/
struct vhost_virtqueue {
union {
struct vring_desc *desc;
struct vring_packed_desc *desc_packed;
};
union {
struct vring_avail *avail;
struct vring_packed_desc_event *driver_event;
};
union {
struct vring_used *used;
struct vring_packed_desc_event *device_event;
};
uint32_t size;
uint16_t last_avail_idx;
uint16_t last_used_idx;
/* Last used index we notify to front end. */
uint16_t signalled_used;
bool signalled_used_valid;
#define VIRTIO_INVALID_EVENTFD (-1)
#define VIRTIO_UNINITIALIZED_EVENTFD (-2)
/* Backend value to determine if device should started/stopped */
int backend;
int enabled;
int access_ok;
rte_spinlock_t access_lock;
/* Used to notify the guest (trigger interrupt) */
int callfd;
/* Currently unused as polling mode is enabled */
int kickfd;
/* Physical address of used ring, for logging */
uint64_t log_guest_addr;
uint16_t nr_zmbuf;
uint16_t zmbuf_size;
uint16_t last_zmbuf_idx;
struct zcopy_mbuf *zmbufs;
struct zcopy_mbuf_list zmbuf_list;
union {
struct vring_used_elem *shadow_used_split;
struct vring_used_elem_packed *shadow_used_packed;
};
uint16_t shadow_used_idx;
struct vhost_vring_addr ring_addrs;
struct batch_copy_elem *batch_copy_elems;
uint16_t batch_copy_nb_elems;
bool used_wrap_counter;
bool avail_wrap_counter;
struct log_cache_entry log_cache[VHOST_LOG_CACHE_NR];
uint16_t log_cache_nb_elem;
rte_rwlock_t iotlb_lock;
rte_rwlock_t iotlb_pending_lock;
struct rte_mempool *iotlb_pool;
TAILQ_HEAD(, vhost_iotlb_entry) iotlb_list;
int iotlb_cache_nr;
TAILQ_HEAD(, vhost_iotlb_entry) iotlb_pending_list;
} __rte_cache_aligned;
内存映射完成之后，DPDK就可像客户机的virtio-net驱动一样直接操作其共享内存中的同一结构了。
控制通道-UNIX套接口
QEMU与DPDK通过vhost user套接口交换消息。
DPDK与QEMU的通信遵照标准的vhost-user协议。
消息类型如下：
dpdk-18.08/lib/librte_vhost/vhost_user.h
VhostUserRequest
typedef enum VhostUserRequest {
VHOST_USER_NONE = 0,
VHOST_USER_GET_FEATURES = 1,
VHOST_USER_SET_FEATURES = 2,
VHOST_USER_SET_OWNER = 3,
VHOST_USER_RESET_OWNER = 4,
VHOST_USER_SET_MEM_TABLE = 5,
VHOST_USER_SET_LOG_BASE = 6,
VHOST_USER_SET_LOG_FD = 7,
VHOST_USER_SET_VRING_NUM = 8,
VHOST_USER_SET_VRING_ADDR = 9,
VHOST_USER_SET_VRING_BASE = 10,
VHOST_USER_GET_VRING_BASE = 11,
VHOST_USER_SET_VRING_KICK = 12,
VHOST_USER_SET_VRING_CALL = 13,
VHOST_USER_SET_VRING_ERR = 14,
VHOST_USER_GET_PROTOCOL_FEATURES = 15,
VHOST_USER_SET_PROTOCOL_FEATURES = 16,
VHOST_USER_GET_QUEUE_NUM = 17,
VHOST_USER_SET_VRING_ENABLE = 18,
VHOST_USER_SEND_RARP = 19,
VHOST_USER_NET_SET_MTU = 20,
VHOST_USER_SET_SLAVE_REQ_FD = 21,
VHOST_USER_IOTLB_MSG = 22,
VHOST_USER_CRYPTO_CREATE_SESS = 26,
VHOST_USER_CRYPTO_CLOSE_SESS = 27,
VHOST_USER_MAX = 28
} VhostUserRequest;
VhostUserMsg
typedef struct VhostUserMsg {
union {
uint32_t master; /* a VhostUserRequest value */
uint32_t slave; /* a VhostUserSlaveRequest value*/
} request;
#define VHOST_USER_VERSION_MASK 0x3
#define VHOST_USER_REPLY_MASK (0x1 << 2)
#define VHOST_USER_NEED_REPLY (0x1 << 3)
uint32_t flags;
uint32_t size; /* the following payload size */
union {
#define VHOST_USER_VRING_IDX_MASK 0xff
#define VHOST_USER_VRING_NOFD_MASK (0x1<<8)
uint64_t u64;
struct vhost_vring_state state;
struct vhost_vring_addr addr;
VhostUserMemory memory;
VhostUserLog log;
struct vhost_iotlb_msg iotlb;
VhostUserCryptoSessionParam crypto_session;
VhostUserVringArea area;
} payload;
int fds[VHOST_MEMORY_MAX_NREGIONS];
} __attribute((packed)) VhostUserMsg;
DPDK使用如下函数处理接收到的消息：
dpdk-18.08/lib/librte_vhost/vhost_user.c
vhost_user_msg_handler()
int
vhost_user_msg_handler(int vid, int fd)
{
struct virtio_net *dev;
struct VhostUserMsg msg;
struct rte_vdpa_device *vdpa_dev;
int did = -1;
int ret;
int unlock_required = 0;
uint32_t skip_master = 0;
dev = get_device(vid);
if (dev == NULL)
return -1;
if (!dev->notify_ops) {
dev->notify_ops = vhost_driver_callback_get(dev->ifname);
if (!dev->notify_ops) {
RTE_LOG(ERR, VHOST_CONFIG,
"failed to get callback ops for driver %s\n",
dev->ifname);
return -1;
}
}
ret = read_vhost_message(fd, &msg);
if (ret <= 0 || msg.request.master >= VHOST_USER_MAX) {
if (ret < 0)
RTE_LOG(ERR, VHOST_CONFIG,
"vhost read message failed\n");
else if (ret == 0)
RTE_LOG(INFO, VHOST_CONFIG,
"vhost peer closed\n");
else
RTE_LOG(ERR, VHOST_CONFIG,
"vhost read incorrect message\n");
return -1;
}
ret = 0;
if (msg.request.master != VHOST_USER_IOTLB_MSG)
RTE_LOG(INFO, VHOST_CONFIG, "read message %s\n",
vhost_message_str[msg.request.master]);
else
RTE_LOG(DEBUG, VHOST_CONFIG, "read message %s\n",
vhost_message_str[msg.request.master]);
ret = vhost_user_check_and_alloc_queue_pair(dev, &msg);
if (ret < 0) {
RTE_LOG(ERR, VHOST_CONFIG,
"failed to alloc queue\n");
return -1;
}
/*
* Note: we don't lock all queues on VHOST_USER_GET_VRING_BASE
* and VHOST_USER_RESET_OWNER, since it is sent when virtio stops
* and device is destroyed. destroy_device waits for queues to be
* inactive, so it is safe. Otherwise taking the access_lock
* would cause a dead lock.
*/
switch (msg.request.master) {
case VHOST_USER_SET_FEATURES:
case VHOST_USER_SET_PROTOCOL_FEATURES:
case VHOST_USER_SET_OWNER:
case VHOST_USER_SET_MEM_TABLE:
case VHOST_USER_SET_LOG_BASE:
case VHOST_USER_SET_LOG_FD:
case VHOST_USER_SET_VRING_NUM:
case VHOST_USER_SET_VRING_ADDR:
case VHOST_USER_SET_VRING_BASE:
case VHOST_USER_SET_VRING_KICK:
case VHOST_USER_SET_VRING_CALL:
case VHOST_USER_SET_VRING_ERR:
case VHOST_USER_SET_VRING_ENABLE:
case VHOST_USER_SEND_RARP:
case VHOST_USER_NET_SET_MTU:
case VHOST_USER_SET_SLAVE_REQ_FD:
vhost_user_lock_all_queue_pairs(dev);
unlock_required = 1;
break;
default:
break;
}
if (dev->extern_ops.pre_msg_handle) {
uint32_t need_reply;
ret = (*dev->extern_ops.pre_msg_handle)(dev->vid,
(void *)&msg, &need_reply, &skip_master);
if (ret < 0)
goto skip_to_reply;
if (need_reply)
send_vhost_reply(fd, &msg);
if (skip_master)
goto skip_to_post_handle;
}
switch (msg.request.master) {
case VHOST_USER_GET_FEATURES:
msg.payload.u64 = vhost_user_get_features(dev);
msg.size = sizeof(msg.payload.u64);
send_vhost_reply(fd, &msg);
break;
case VHOST_USER_SET_FEATURES:
ret = vhost_user_set_features(dev, msg.payload.u64);
break;
case VHOST_USER_GET_PROTOCOL_FEATURES:
vhost_user_get_protocol_features(dev, &msg);
send_vhost_reply(fd, &msg);
break;
case VHOST_USER_SET_PROTOCOL_FEATURES:
ret = vhost_user_set_protocol_features(dev, msg.payload.u64);
break;
case VHOST_USER_SET_OWNER:
ret = vhost_user_set_owner();
break;
case VHOST_USER_RESET_OWNER:
ret = vhost_user_reset_owner(dev);
break;
case VHOST_USER_SET_MEM_TABLE:
ret = vhost_user_set_mem_table(&dev, &msg);
break;
case VHOST_USER_SET_LOG_BASE:
ret = vhost_user_set_log_base(dev, &msg);
if (ret)
goto skip_to_reply;
/* it needs a reply */
msg.size = sizeof(msg.payload.u64);
send_vhost_reply(fd, &msg);
break;
case VHOST_USER_SET_LOG_FD:
close(msg.fds[0]);
RTE_LOG(INFO, VHOST_CONFIG, "not implemented.\n");
break;
case VHOST_USER_SET_VRING_NUM:
ret = vhost_user_set_vring_num(dev, &msg);
break;
case VHOST_USER_SET_VRING_ADDR:
ret = vhost_user_set_vring_addr(&dev, &msg);
break;
case VHOST_USER_SET_VRING_BASE:
ret = vhost_user_set_vring_base(dev, &msg);
break;
case VHOST_USER_GET_VRING_BASE:
ret = vhost_user_get_vring_base(dev, &msg);
if (ret)
goto skip_to_reply;
msg.size = sizeof(msg.payload.state);
send_vhost_reply(fd, &msg);
break;
case VHOST_USER_SET_VRING_KICK:
ret = vhost_user_set_vring_kick(&dev, &msg);
break;
case VHOST_USER_SET_VRING_CALL:
vhost_user_set_vring_call(dev, &msg);
break;
case VHOST_USER_SET_VRING_ERR:
if (!(msg.payload.u64 & VHOST_USER_VRING_NOFD_MASK))
close(msg.fds[0]);
RTE_LOG(INFO, VHOST_CONFIG, "not implemented\n");
break;
case VHOST_USER_GET_QUEUE_NUM:
msg.payload.u64 = (uint64_t)vhost_user_get_queue_num(dev);
msg.size = sizeof(msg.payload.u64);
send_vhost_reply(fd, &msg);
break;
case VHOST_USER_SET_VRING_ENABLE:
ret = vhost_user_set_vring_enable(dev, &msg);
break;
case VHOST_USER_SEND_RARP:
ret = vhost_user_send_rarp(dev, &msg);
break;
case VHOST_USER_NET_SET_MTU:
ret = vhost_user_net_set_mtu(dev, &msg);
break;
case VHOST_USER_SET_SLAVE_REQ_FD:
ret = vhost_user_set_req_fd(dev, &msg);
break;
case VHOST_USER_IOTLB_MSG:
ret = vhost_user_iotlb_msg(&dev, &msg);
break;
default:
ret = -1;
break;
}
skip_to_post_handle:
if (!ret && dev->extern_ops.post_msg_handle) {
uint32_t need_reply;
ret = (*dev->extern_ops.post_msg_handle)(
dev->vid, (void *)&msg, &need_reply);
if (ret < 0)
goto skip_to_reply;
if (need_reply)
send_vhost_reply(fd, &msg);
}
skip_to_reply:
if (unlock_required)
vhost_user_unlock_all_queue_pairs(dev);
if (msg.flags & VHOST_USER_NEED_REPLY) {
msg.payload.u64 = !!ret;
msg.size = sizeof(msg.payload.u64);
send_vhost_reply(fd, &msg);
} else if (ret) {
RTE_LOG(ERR, VHOST_CONFIG,
"vhost message handling failed.\n");
return -1;
}
if (!(dev->flags & VIRTIO_DEV_RUNNING) && virtio_is_ready(dev)) {
dev->flags |= VIRTIO_DEV_READY;
if (!(dev->flags & VIRTIO_DEV_RUNNING)) {
if (dev->dequeue_zero_copy) {
RTE_LOG(INFO, VHOST_CONFIG,
"dequeue zero copy is enabled\n");
}
if (dev->notify_ops->new_device(dev->vid) == 0)
dev->flags |= VIRTIO_DEV_RUNNING;
}
}
did = dev->vdpa_dev_id;
vdpa_dev = rte_vdpa_get_device(did);
if (vdpa_dev && virtio_is_ready(dev) &&
!(dev->flags & VIRTIO_DEV_VDPA_CONFIGURED) &&
msg.request.master == VHOST_USER_SET_VRING_ENABLE) {
if (vdpa_dev->ops->dev_conf)
vdpa_dev->ops->dev_conf(dev->vid);
dev->flags |= VIRTIO_DEV_VDPA_CONFIGURED;
if (vhost_user_host_notifier_ctrl(dev->vid, true) != 0) {
RTE_LOG(INFO, VHOST_CONFIG,
"(%d) software relay is used for vDPA, performance may be low.\n",
dev->vid);
}
}
return 0;
}
还有dpdk-18.08/lib/librte_vhost/vhost_user.c：
read_vhost_message()
/* return bytes# of read on success or negative val on failure. */
static int
read_vhost_message(int sockfd, struct VhostUserMsg *msg)
{
int ret;
ret = read_fd_message(sockfd, (char *)msg, VHOST_USER_HDR_SIZE,
msg->fds, VHOST_MEMORY_MAX_NREGIONS);
if (ret <= 0)
return ret;
if (msg->size) {
if (msg->size > sizeof(msg->payload)) {
RTE_LOG(ERR, VHOST_CONFIG,
"invalid msg size: %d\n", msg->size);
return -1;
}
ret = read(sockfd, &msg->payload, msg->size);
if (ret <= 0)
return ret;
if (ret != (int)msg->size) {
RTE_LOG(ERR, VHOST_CONFIG,
"read control message failed\n");
return -1;
}
}
return ret;
}
read_fd_message()
/* return bytes# of read on success or negative val on failure. */
int
read_fd_message(int sockfd, char *buf, int buflen, int *fds, int fd_num)
{
struct iovec iov;
struct msghdr msgh;
size_t fdsize = fd_num * sizeof(int);
char control[CMSG_SPACE(fdsize)];
struct cmsghdr *cmsg;
int got_fds = 0;
int ret;
memset(&msgh, 0, sizeof(msgh));
iov.iov_base = buf;
iov.iov_len = buflen;
msgh.msg_iov = &iov;
msgh.msg_iovlen = 1;
msgh.msg_control = control;
msgh.msg_controllen = sizeof(control);
ret = recvmsg(sockfd, &msgh, 0);
if (ret <= 0) {
RTE_LOG(ERR, VHOST_CONFIG, "recvmsg failed\n");
return ret;
}
if (msgh.msg_flags & (MSG_TRUNC | MSG_CTRUNC)) {
RTE_LOG(ERR, VHOST_CONFIG, "truncted msg\n");
return -1;
}
for (cmsg = CMSG_FIRSTHDR(&msgh); cmsg != NULL;
cmsg = CMSG_NXTHDR(&msgh, cmsg)) {
if ((cmsg->cmsg_level == SOL_SOCKET) &&
(cmsg->cmsg_type == SCM_RIGHTS)) {
got_fds = (cmsg->cmsg_len - CMSG_LEN(0)) / sizeof(int);
memcpy(fds, CMSG_DATA(cmsg), got_fds * sizeof(int));
break;
}
}
/* Clear out unused file descriptors */
while (got_fds < fd_num)
fds[got_fds++] = -1;
return ret;
}
DPDK向外发送消息使用如下函数
dpdk-18.08/lib/librte_vhost/vhost_user.c
send_vhost_message()
static int
send_vhost_message(int sockfd, struct VhostUserMsg *msg, int *fds, int fd_num)
{
if (!msg)
return 0;
return send_fd_message(sockfd, (char *)msg,
VHOST_USER_HDR_SIZE + msg->size, fds, fd_num);
}
send_fd_message()
int
send_fd_message(int sockfd, char *buf, int buflen, int *fds, int fd_num)
{
struct iovec iov;
struct msghdr msgh;
size_t fdsize = fd_num * sizeof(int);
char control[CMSG_SPACE(fdsize)];
struct cmsghdr *cmsg;
int ret;
memset(&msgh, 0, sizeof(msgh));
iov.iov_base = buf;
iov.iov_len = buflen;
msgh.msg_iov = &iov;
msgh.msg_iovlen = 1;
if (fds && fd_num > 0) {
msgh.msg_control = control;
msgh.msg_controllen = sizeof(control);
cmsg = CMSG_FIRSTHDR(&msgh);
if (cmsg == NULL) {
RTE_LOG(ERR, VHOST_CONFIG, "cmsg == NULL\n");
errno = EINVAL;
return -1;
}
cmsg->cmsg_len = CMSG_LEN(fdsize);
cmsg->cmsg_level = SOL_SOCKET;
cmsg->cmsg_type = SCM_RIGHTS;
memcpy(CMSG_DATA(cmsg), fds, fdsize);
} else {
msgh.msg_control = NULL;
msgh.msg_controllen = 0;
}
do {
ret = sendmsg(sockfd, &msgh, MSG_NOSIGNAL);
} while (ret < 0 && errno == EINTR);
if (ret < 0) {
RTE_LOG(ERR, VHOST_CONFIG, "sendmsg error\n");
return ret;
}
return ret;
}
QEMU与之相对应的接收函数为：
qemu-3.0.0/contrib/libvhost-user/libvhost-user.c
vu_process_message()
static bool
vu_process_message(VuDev *dev, VhostUserMsg *vmsg)
{
int do_reply = 0;
/* Print out generic part of the request. */
DPRINT("================ Vhost user message ================\n");
DPRINT("Request: %s (%d)\n", vu_request_to_string(vmsg->request),
vmsg->request);
DPRINT("Flags: 0x%x\n", vmsg->flags);
DPRINT("Size: %d\n", vmsg->size);
if (vmsg->fd_num) {
int i;
DPRINT("Fds:");
for (i = 0; i < vmsg->fd_num; i++) {
DPRINT(" %d", vmsg->fds[i]);
}
DPRINT("\n");
}
if (dev->iface->process_msg &&
dev->iface->process_msg(dev, vmsg, &do_reply)) {
return do_reply;
}
switch (vmsg->request) {
case VHOST_USER_GET_FEATURES:
return vu_get_features_exec(dev, vmsg);
case VHOST_USER_SET_FEATURES:
return vu_set_features_exec(dev, vmsg);
case VHOST_USER_GET_PROTOCOL_FEATURES:
return vu_get_protocol_features_exec(dev, vmsg);
case VHOST_USER_SET_PROTOCOL_FEATURES:
return vu_set_protocol_features_exec(dev, vmsg);
case VHOST_USER_SET_OWNER:
return vu_set_owner_exec(dev, vmsg);
case VHOST_USER_RESET_OWNER:
return vu_reset_device_exec(dev, vmsg);
case VHOST_USER_SET_MEM_TABLE:
return vu_set_mem_table_exec(dev, vmsg);
case VHOST_USER_SET_LOG_BASE:
return vu_set_log_base_exec(dev, vmsg);
case VHOST_USER_SET_LOG_FD:
return vu_set_log_fd_exec(dev, vmsg);
case VHOST_USER_SET_VRING_NUM:
return vu_set_vring_num_exec(dev, vmsg);
case VHOST_USER_SET_VRING_ADDR:
return vu_set_vring_addr_exec(dev, vmsg);
case VHOST_USER_SET_VRING_BASE:
return vu_set_vring_base_exec(dev, vmsg);
case VHOST_USER_GET_VRING_BASE:
return vu_get_vring_base_exec(dev, vmsg);
case VHOST_USER_SET_VRING_KICK:
return vu_set_vring_kick_exec(dev, vmsg);
case VHOST_USER_SET_VRING_CALL:
return vu_set_vring_call_exec(dev, vmsg);
case VHOST_USER_SET_VRING_ERR:
return vu_set_vring_err_exec(dev, vmsg);
case VHOST_USER_GET_QUEUE_NUM:
return vu_get_queue_num_exec(dev, vmsg);
case VHOST_USER_SET_VRING_ENABLE:
return vu_set_vring_enable_exec(dev, vmsg);
case VHOST_USER_SET_SLAVE_REQ_FD:
return vu_set_slave_req_fd(dev, vmsg);
case VHOST_USER_GET_CONFIG:
return vu_get_config(dev, vmsg);
case VHOST_USER_SET_CONFIG:
return vu_set_config(dev, vmsg);
case VHOST_USER_NONE:
break;
case VHOST_USER_POSTCOPY_ADVISE:
return vu_set_postcopy_advise(dev, vmsg);
case VHOST_USER_POSTCOPY_LISTEN:
return vu_set_postcopy_listen(dev, vmsg);
case VHOST_USER_POSTCOPY_END:
return vu_set_postcopy_end(dev, vmsg);
default:
vmsg_close_fds(vmsg);
vu_panic(dev, "Unhandled request: %d", vmsg->request);
}
return false;
}
QEMU对应的消息发送函数：
qemu-3.0.0/hw/virtio/vhost-user.c
vhost_user_write()
/* most non-init callers ignore the error */
static int vhost_user_write(struct vhost_dev *dev, VhostUserMsg *msg,
int *fds, int fd_num)
{
struct vhost_user *u = dev->opaque;
CharBackend *chr = u->user->chr;
int ret, size = VHOST_USER_HDR_SIZE + msg->hdr.size;
/*
* For non-vring specific requests, like VHOST_USER_SET_MEM_TABLE,
* we just need send it once in the first time. For later such
* request, we just ignore it.
*/
if (vhost_user_one_time_request(msg->hdr.request) && dev->vq_index != 0) {
msg->hdr.flags &= ~VHOST_USER_NEED_REPLY_MASK;
return 0;
}
if (qemu_chr_fe_set_msgfds(chr, fds, fd_num) < 0) {
error_report("Failed to set msg fds.");
return -1;
}
ret = qemu_chr_fe_write_all(chr, (const uint8_t *) msg, size);
if (ret != size) {
error_report("Failed to write msg."
" Wrote %d instead of %d.", ret, size);
return -1;
}
return 0;
}
DPDK UNIX套接口的注册和消息交互
neutron控制Open vSwitch创建一个名称为vhuxxxxxxxx-xx的接口。在OVS内部，此名称保存在netdev结构体的成员name中（netdev->name）。
当创建vhost user接口时，Open vSwitch控制DPDK注册一个新的vhost-user UNIX套接口。套接口的路径为vhost_sock_dir加netdev->name加设备的dev->vhost_id。
通过设置RTE_VHOST_USER_CLIENT标志，OVS可请求创建vhost user套接口的客户端模式。
OVS函数netdev_dpdk_vhost_construct调用DPDK的rte_vhost_driver_register函数，其又调用vhost_user_create_server或者vhost_user_create_client函数创建套接口。默认使用前者创建服务端模式的套接口，如果设置了RTE_VHOST_USER_CLIENT标志，创建客户端模式套接口。
相关的函数调用关系如下：
netdev_dpdk_vhost_construct定义在文件openvswitch-2.9.2/lib/netdev-dpdk.c
netdev_dpdk_vhost_construct()
static int
netdev_dpdk_vhost_construct(struct netdev *netdev)
{
struct netdev_dpdk *dev = netdev_dpdk_cast(netdev);
const char *name = netdev->name;
int err;
/* 'name' is appended to 'vhost_sock_dir' and used to create a socket in
* the file system. '/' or '\' would traverse directories, so they're not
* acceptable in 'name'. */
if (strchr(name, '/') || strchr(name, '\\')) {
VLOG_ERR("\"%s\" is not a valid name for a vhost-user port. "
"A valid name must not include '/' or '\\'",
name);
return EINVAL;
}
ovs_mutex_lock(&dpdk_mutex);
/* Take the name of the vhost-user port and append it to the location where
* the socket is to be created, then register the socket.
*/
snprintf(dev->vhost_id, sizeof dev->vhost_id, "%s/%s",
dpdk_get_vhost_sock_dir(), name);
dev->vhost_driver_flags &= ~RTE_VHOST_USER_CLIENT;
err = rte_vhost_driver_register(dev->vhost_id, dev->vhost_driver_flags);
if (err) {
VLOG_ERR("vhost-user socket device setup failure for socket %s\n",
dev->vhost_id);
goto out;
} else {
fatal_signal_add_file_to_unlink(dev->vhost_id);
VLOG_INFO("Socket %s created for vhost-user port %s\n",
dev->vhost_id, name);
}
err = rte_vhost_driver_callback_register(dev->vhost_id,
&virtio_net_device_ops);
if (err) {
VLOG_ERR("rte_vhost_driver_callback_register failed for vhost user "
"port: %s\n", name);
goto out;
}
err = rte_vhost_driver_disable_features(dev->vhost_id,
1ULL << VIRTIO_NET_F_HOST_TSO4
| 1ULL << VIRTIO_NET_F_HOST_TSO6
| 1ULL << VIRTIO_NET_F_CSUM);
if (err) {
VLOG_ERR("rte_vhost_driver_disable_features failed for vhost user "
"port: %s\n", name);
goto out;
}
err = rte_vhost_driver_start(dev->vhost_id);
if (err) {
VLOG_ERR("rte_vhost_driver_start failed for vhost user "
"port: %s\n", name);
goto out;
}
err = vhost_common_construct(netdev);
if (err) {
VLOG_ERR("vhost_common_construct failed for vhost user "
"port: %s\n", name);
}
out:
ovs_mutex_unlock(&dpdk_mutex);
VLOG_WARN_ONCE("dpdkvhostuser ports are considered deprecated; "
"please migrate to dpdkvhostuserclient ports.");
return err;
}
netdev_dpdk_vhost_construct函数调用rte_vhost_driver_register。以下代码均定义在dpdk-18.08/lib/librte_vhost/socket.c
rte_vhost_driver_register()
/*
* Register a new vhost-user socket; here we could act as server
* (the default case), or client (when RTE_VHOST_USER_CLIENT) flag
* is set.
*/
int
rte_vhost_driver_register(const char *path, uint64_t flags)
{
int ret = -1;
struct vhost_user_socket *vsocket;
if (!path)
return -1;
pthread_mutex_lock(&vhost_user.mutex);
if (vhost_user.vsocket_cnt == MAX_VHOST_SOCKET) {
RTE_LOG(ERR, VHOST_CONFIG,
"error: the number of vhost sockets reaches maximum\n");
goto out;
}
vsocket = malloc(sizeof(struct vhost_user_socket));
if (!vsocket)
goto out;
memset(vsocket, 0, sizeof(struct vhost_user_socket));
vsocket->path = strdup(path);
if (vsocket->path == NULL) {
RTE_LOG(ERR, VHOST_CONFIG,
"error: failed to copy socket path string\n");
vhost_user_socket_mem_free(vsocket);
goto out;
}
TAILQ_INIT(&vsocket->conn_list);
ret = pthread_mutex_init(&vsocket->conn_mutex, NULL);
if (ret) {
RTE_LOG(ERR, VHOST_CONFIG,
"error: failed to init connection mutex\n");
goto out_free;
}
vsocket->dequeue_zero_copy = flags & RTE_VHOST_USER_DEQUEUE_ZERO_COPY;
/*
* Set the supported features correctly for the builtin vhost-user
* net driver.
*
* Applications know nothing about features the builtin virtio net
* driver (virtio_net.c) supports, thus it's not possible for them
* to invoke rte_vhost_driver_set_features(). To workaround it, here
* we set it unconditionally. If the application want to implement
* another vhost-user driver (say SCSI), it should call the
* rte_vhost_driver_set_features(), which will overwrite following
* two values.
*/
vsocket->use_builtin_virtio_net = true;
vsocket->supported_features = VIRTIO_NET_SUPPORTED_FEATURES;
vsocket->features = VIRTIO_NET_SUPPORTED_FEATURES;
/* Dequeue zero copy can't assure descriptors returned in order */
if (vsocket->dequeue_zero_copy) {
vsocket->supported_features &= ~(1ULL << VIRTIO_F_IN_ORDER);
vsocket->features &= ~(1ULL << VIRTIO_F_IN_ORDER);
}
if (!(flags & RTE_VHOST_USER_IOMMU_SUPPORT)) {
vsocket->supported_features &= ~(1ULL << VIRTIO_F_IOMMU_PLATFORM);
vsocket->features &= ~(1ULL << VIRTIO_F_IOMMU_PLATFORM);
}
if ((flags & RTE_VHOST_USER_CLIENT) != 0) {
vsocket->reconnect = !(flags & RTE_VHOST_USER_NO_RECONNECT);
if (vsocket->reconnect && reconn_tid == 0) {
if (vhost_user_reconnect_init() != 0)
goto out_mutex;
}
} else {
vsocket->is_server = true;
}
ret = create_unix_socket(vsocket);
if (ret < 0) {
goto out_mutex;
}
vhost_user.vsockets[vhost_user.vsocket_cnt++] = vsocket;
pthread_mutex_unlock(&vhost_user.mutex);
return ret;
out_mutex:
if (pthread_mutex_destroy(&vsocket->conn_mutex)) {
RTE_LOG(ERR, VHOST_CONFIG,
"error: failed to destroy connection mutex\n");
}
out_free:
vhost_user_socket_mem_free(vsocket);
out:
pthread_mutex_unlock(&vhost_user.mutex);
return ret;
}
create_unix_socket()
static int
create_unix_socket(struct vhost_user_socket *vsocket)
{
int fd;
struct sockaddr_un *un = &vsocket->un;
fd = socket(AF_UNIX, SOCK_STREAM, 0);
if (fd < 0)
return -1;
RTE_LOG(INFO, VHOST_CONFIG, "vhost-user %s: socket created, fd: %d\n",
vsocket->is_server ? "server" : "client", fd);
if (!vsocket->is_server && fcntl(fd, F_SETFL, O_NONBLOCK)) {
RTE_LOG(ERR, VHOST_CONFIG,
"vhost-user: can't set nonblocking mode for socket, fd: "
"%d (%s)\n", fd, strerror(errno));
close(fd);
return -1;
}
memset(un, 0, sizeof(*un));
un->sun_family = AF_UNIX;
strncpy(un->sun_path, vsocket->path, sizeof(un->sun_path));
un->sun_path[sizeof(un->sun_path) - 1] = '\0';
vsocket->socket_fd = fd;
return 0;
}
netdev_dpdk_vhost_construct函数调用rte_vhost_driver_start。定义在dpdk-18.08/lib/librte_vhost/socket.c
rte_vhost_driver_start()
int
rte_vhost_driver_start(const char *path)
{
struct vhost_user_socket *vsocket;
static pthread_t fdset_tid;
pthread_mutex_lock(&vhost_user.mutex);
vsocket = find_vhost_user_socket(path);
pthread_mutex_unlock(&vhost_user.mutex);
if (!vsocket)
return -1;
if (fdset_tid == 0) {
/**
* create a pipe which will be waited by poll and notified to
* rebuild the wait list of poll.
*/
if (fdset_pipe_init(&vhost_user.fdset) < 0) {
RTE_LOG(ERR, VHOST_CONFIG,
"failed to create pipe for vhost fdset\n");
return -1;
}
int ret = rte_ctrl_thread_create(&fdset_tid,
"vhost-events", NULL, fdset_event_dispatch,
&vhost_user.fdset);
if (ret != 0) {
RTE_LOG(ERR, VHOST_CONFIG,
"failed to create fdset handling thread");
fdset_pipe_uninit(&vhost_user.fdset);
return -1;
}
}
if (vsocket->is_server)
return vhost_user_start_server(vsocket);
else
return vhost_user_start_client(vsocket);
}
vhost_user_create_server调用vhost_user_server_new_connection:
以下的3个函数调用vhost_user_add_connection：
vhost_user_server_new_connection()
static void
vhost_user_server_new_connection(int fd, void *dat, int *remove __rte_unused)
{
struct vhost_user_socket *vsocket = dat;
fd = accept(fd, NULL, NULL);
if (fd < 0)
return;
RTE_LOG(INFO, VHOST_CONFIG, "new vhost user connection is %d\n", fd);
vhost_user_add_connection(fd, vsocket);
}
vhost_user_client_reconnect()
static void *
vhost_user_client_reconnect(void *arg __rte_unused)
{
int ret;
struct vhost_user_reconnect *reconn, *next;
while (1) {
pthread_mutex_lock(&reconn_list.mutex);
/*
* An equal implementation of TAILQ_FOREACH_SAFE,
* which does not exist on all platforms.
*/
for (reconn = TAILQ_FIRST(&reconn_list.head);
reconn != NULL; reconn = next) {
next = TAILQ_NEXT(reconn, next);
ret = vhost_user_connect_nonblock(reconn->fd,
(struct sockaddr *)&reconn->un,
sizeof(reconn->un));
if (ret == -2) {
close(reconn->fd);
RTE_LOG(ERR, VHOST_CONFIG,
"reconnection for fd %d failed\n",
reconn->fd);
goto remove_fd;
}
if (ret == -1)
continue;
RTE_LOG(INFO, VHOST_CONFIG,
"%s: connected\n", reconn->vsocket->path);
vhost_user_add_connection(reconn->fd, reconn->vsocket);
remove_fd:
TAILQ_REMOVE(&reconn_list.head, reconn, next);
free(reconn);
}
pthread_mutex_unlock(&reconn_list.mutex);
sleep(1);
}
return NULL;
}
vhost_user_start_client()
static int
vhost_user_start_client(struct vhost_user_socket *vsocket)
{
int ret;
int fd = vsocket->socket_fd;
const char *path = vsocket->path;
struct vhost_user_reconnect *reconn;
ret = vhost_user_connect_nonblock(fd, (struct sockaddr *)&vsocket->un,
sizeof(vsocket->un));
if (ret == 0) {
vhost_user_add_connection(fd, vsocket);
return 0;
}
RTE_LOG(WARNING, VHOST_CONFIG,
"failed to connect to %s: %s\n",
path, strerror(errno));
if (ret == -2 || !vsocket->reconnect) {
close(fd);
return -1;
}
RTE_LOG(INFO, VHOST_CONFIG, "%s: reconnecting...\n", path);
reconn = malloc(sizeof(*reconn));
if (reconn == NULL) {
RTE_LOG(ERR, VHOST_CONFIG,
"failed to allocate memory for reconnect\n");
close(fd);
return -1;
}
reconn->un = vsocket->un;
reconn->fd = fd;
reconn->vsocket = vsocket;
pthread_mutex_lock(&reconn_list.mutex);
TAILQ_INSERT_TAIL(&reconn_list.head, reconn, next);
pthread_mutex_unlock(&reconn_list.mutex);
return 0;
}
vhost_user_connect_nonblock()
static int
vhost_user_connect_nonblock(int fd, struct sockaddr *un, size_t sz)
{
int ret, flags;
ret = connect(fd, un, sz);
if (ret < 0 && errno != EISCONN)
return -1;
flags = fcntl(fd, F_GETFL, 0);
if (flags < 0) {
RTE_LOG(ERR, VHOST_CONFIG,
"can't get flags for connfd %d\n", fd);
return -2;
}
if ((flags & O_NONBLOCK) && fcntl(fd, F_SETFL, flags & ~O_NONBLOCK)) {
RTE_LOG(ERR, VHOST_CONFIG,
"can't disable nonblocking on fd %d\n", fd);
return -2;
}
return 0;
}
vhost_user_start_server()
static int
vhost_user_start_server(struct vhost_user_socket *vsocket)
{
int ret;
int fd = vsocket->socket_fd;
const char *path = vsocket->path;
/*
* bind () may fail if the socket file with the same name already
* exists. But the library obviously should not delete the file
* provided by the user, since we can not be sure that it is not
* being used by other applications. Moreover, many applications form
* socket names based on user input, which is prone to errors.
*
* The user must ensure that the socket does not exist before
* registering the vhost driver in server mode.
*/
ret = bind(fd, (struct sockaddr *)&vsocket->un, sizeof(vsocket->un));
if (ret < 0) {
RTE_LOG(ERR, VHOST_CONFIG,
"failed to bind to %s: %s; remove it and try again\n",
path, strerror(errno));
goto err;
}
RTE_LOG(INFO, VHOST_CONFIG, "bind to %s\n", path);
ret = listen(fd, MAX_VIRTIO_BACKLOG);
if (ret < 0)
goto err;
ret = fdset_add(&vhost_user.fdset, fd, vhost_user_server_new_connection,
NULL, vsocket);
if (ret < 0) {
RTE_LOG(ERR, VHOST_CONFIG,
"failed to add listen fd %d to vhost server fdset\n",
fd);
goto err;
}
return 0;
err:
close(fd);
return -1;
}
vhost_user_add_connection()
static void
vhost_user_add_connection(int fd, struct vhost_user_socket *vsocket)
{
int vid;
size_t size;
struct vhost_user_connection *conn;
int ret;
if (vsocket == NULL)
return;
conn = malloc(sizeof(*conn));
if (conn == NULL) {
close(fd);
return;
}
vid = vhost_new_device();
if (vid == -1) {
goto err;
}
size = strnlen(vsocket->path, PATH_MAX);
vhost_set_ifname(vid, vsocket->path, size);
vhost_set_builtin_virtio_net(vid, vsocket->use_builtin_virtio_net);
vhost_attach_vdpa_device(vid, vsocket->vdpa_dev_id);
if (vsocket->dequeue_zero_copy)
vhost_enable_dequeue_zero_copy(vid);
RTE_LOG(INFO, VHOST_CONFIG, "new device, handle is %d\n", vid);
if (vsocket->notify_ops->new_connection) {
ret = vsocket->notify_ops->new_connection(vid);
if (ret < 0) {
RTE_LOG(ERR, VHOST_CONFIG,
"failed to add vhost user connection with fd %d\n",
fd);
goto err;
}
}
conn->connfd = fd;
conn->vsocket = vsocket;
conn->vid = vid;
ret = fdset_add(&vhost_user.fdset, fd, vhost_user_read_cb,
NULL, conn);
if (ret < 0) {
RTE_LOG(ERR, VHOST_CONFIG,
"failed to add fd %d into vhost server fdset\n",
fd);
if (vsocket->notify_ops->destroy_connection)
vsocket->notify_ops->destroy_connection(conn->vid);
goto err;
}
pthread_mutex_lock(&vsocket->conn_mutex);
TAILQ_INSERT_TAIL(&vsocket->conn_list, conn, next);
pthread_mutex_unlock(&vsocket->conn_mutex);
fdset_pipe_notify(&vhost_user.fdset);
return;
err:
free(conn);
close(fd);
}
vhost_user_add_connection接下来执行vhost_user_read_cb函数，其又调用vhost_user_msg_handler函数处理接收到的消息。
vhost_user_read_cb()
static void
vhost_user_read_cb(int connfd, void *dat, int *remove)
{
struct vhost_user_connection *conn = dat;
struct vhost_user_socket *vsocket = conn->vsocket;
int ret;
ret = vhost_user_msg_handler(conn->vid, connfd);
if (ret < 0) {
close(connfd);
*remove = 1;
vhost_destroy_device(conn->vid);
if (vsocket->notify_ops->destroy_connection)
vsocket->notify_ops->destroy_connection(conn->vid);
pthread_mutex_lock(&vsocket->conn_mutex);
TAILQ_REMOVE(&vsocket->conn_list, conn, next);
pthread_mutex_unlock(&vsocket->conn_mutex);
free(conn);
if (vsocket->reconnect) {
create_unix_socket(vsocket);
vhost_user_start_client(vsocket);
}
}
}
dpdk-18.08/lib/librte_vhost/vhost_user.c
vhost_user_msg_handler()
int
vhost_user_msg_handler(int vid, int fd)
{
struct virtio_net *dev;
struct VhostUserMsg msg;
struct rte_vdpa_device *vdpa_dev;
int did = -1;
int ret;
int unlock_required = 0;
uint32_t skip_master = 0;
dev = get_device(vid);
if (dev == NULL)
return -1;
if (!dev->notify_ops) {
dev->notify_ops = vhost_driver_callback_get(dev->ifname);
if (!dev->notify_ops) {
RTE_LOG(ERR, VHOST_CONFIG,
"failed to get callback ops for driver %s\n",
dev->ifname);
return -1;
}
}
ret = read_vhost_message(fd, &msg);
if (ret <= 0 || msg.request.master >= VHOST_USER_MAX) {
if (ret < 0)
RTE_LOG(ERR, VHOST_CONFIG,
"vhost read message failed\n");
else if (ret == 0)
RTE_LOG(INFO, VHOST_CONFIG,
"vhost peer closed\n");
else
RTE_LOG(ERR, VHOST_CONFIG,
"vhost read incorrect message\n");
return -1;
}
ret = 0;
if (msg.request.master != VHOST_USER_IOTLB_MSG)
RTE_LOG(INFO, VHOST_CONFIG, "read message %s\n",
vhost_message_str[msg.request.master]);
else
RTE_LOG(DEBUG, VHOST_CONFIG, "read message %s\n",
vhost_message_str[msg.request.master]);
ret = vhost_user_check_and_alloc_queue_pair(dev, &msg);
if (ret < 0) {
RTE_LOG(ERR, VHOST_CONFIG,
"failed to alloc queue\n");
return -1;
}
/*
* Note: we don't lock all queues on VHOST_USER_GET_VRING_BASE
* and VHOST_USER_RESET_OWNER, since it is sent when virtio stops
* and device is destroyed. destroy_device waits for queues to be
* inactive, so it is safe. Otherwise taking the access_lock
* would cause a dead lock.
*/
switch (msg.request.master) {
case VHOST_USER_SET_FEATURES:
case VHOST_USER_SET_PROTOCOL_FEATURES:
case VHOST_USER_SET_OWNER:
case VHOST_USER_SET_MEM_TABLE:
case VHOST_USER_SET_LOG_BASE:
case VHOST_USER_SET_LOG_FD:
case VHOST_USER_SET_VRING_NUM:
case VHOST_USER_SET_VRING_ADDR:
case VHOST_USER_SET_VRING_BASE:
case VHOST_USER_SET_VRING_KICK:
case VHOST_USER_SET_VRING_CALL:
case VHOST_USER_SET_VRING_ERR:
case VHOST_USER_SET_VRING_ENABLE:
case VHOST_USER_SEND_RARP:
case VHOST_USER_NET_SET_MTU:
case VHOST_USER_SET_SLAVE_REQ_FD:
vhost_user_lock_all_queue_pairs(dev);
unlock_required = 1;
break;
default:
break;
}
if (dev->extern_ops.pre_msg_handle) {
uint32_t need_reply;
ret = (*dev->extern_ops.pre_msg_handle)(dev->vid,
(void *)&msg, &need_reply, &skip_master);
if (ret < 0)
goto skip_to_reply;
if (need_reply)
send_vhost_reply(fd, &msg);
if (skip_master)
goto skip_to_post_handle;
}
switch (msg.request.master) {
case VHOST_USER_GET_FEATURES:
msg.payload.u64 = vhost_user_get_features(dev);
msg.size = sizeof(msg.payload.u64);
send_vhost_reply(fd, &msg);
break;
case VHOST_USER_SET_FEATURES:
ret = vhost_user_set_features(dev, msg.payload.u64);
break;
case VHOST_USER_GET_PROTOCOL_FEATURES:
vhost_user_get_protocol_features(dev, &msg);
send_vhost_reply(fd, &msg);
break;
case VHOST_USER_SET_PROTOCOL_FEATURES:
ret = vhost_user_set_protocol_features(dev, msg.payload.u64);
break;
case VHOST_USER_SET_OWNER:
ret = vhost_user_set_owner();
break;
case VHOST_USER_RESET_OWNER:
ret = vhost_user_reset_owner(dev);
break;
case VHOST_USER_SET_MEM_TABLE:
ret = vhost_user_set_mem_table(&dev, &msg);
break;
case VHOST_USER_SET_LOG_BASE:
ret = vhost_user_set_log_base(dev, &msg);
if (ret)
goto skip_to_reply;
/* it needs a reply */
msg.size = sizeof(msg.payload.u64);
send_vhost_reply(fd, &msg);
break;
case VHOST_USER_SET_LOG_FD:
close(msg.fds[0]);
RTE_LOG(INFO, VHOST_CONFIG, "not implemented.\n");
break;
case VHOST_USER_SET_VRING_NUM:
ret = vhost_user_set_vring_num(dev, &msg);
break;
case VHOST_USER_SET_VRING_ADDR:
ret = vhost_user_set_vring_addr(&dev, &msg);
break;
case VHOST_USER_SET_VRING_BASE:
ret = vhost_user_set_vring_base(dev, &msg);
break;
case VHOST_USER_GET_VRING_BASE:
ret = vhost_user_get_vring_base(dev, &msg);
if (ret)
goto skip_to_reply;
msg.size = sizeof(msg.payload.state);
send_vhost_reply(fd, &msg);
break;
case VHOST_USER_SET_VRING_KICK:
ret = vhost_user_set_vring_kick(&dev, &msg);
break;
case VHOST_USER_SET_VRING_CALL:
vhost_user_set_vring_call(dev, &msg);
break;
case VHOST_USER_SET_VRING_ERR:
if (!(msg.payload.u64 & VHOST_USER_VRING_NOFD_MASK))
close(msg.fds[0]);
RTE_LOG(INFO, VHOST_CONFIG, "not implemented\n");
break;
case VHOST_USER_GET_QUEUE_NUM:
msg.payload.u64 = (uint64_t)vhost_user_get_queue_num(dev);
msg.size = sizeof(msg.payload.u64);
send_vhost_reply(fd, &msg);
break;
case VHOST_USER_SET_VRING_ENABLE:
ret = vhost_user_set_vring_enable(dev, &msg);
break;
case VHOST_USER_SEND_RARP:
ret = vhost_user_send_rarp(dev, &msg);
break;
case VHOST_USER_NET_SET_MTU:
ret = vhost_user_net_set_mtu(dev, &msg);
break;
case VHOST_USER_SET_SLAVE_REQ_FD:
ret = vhost_user_set_req_fd(dev, &msg);
break;
case VHOST_USER_IOTLB_MSG:
ret = vhost_user_iotlb_msg(&dev, &msg);
break;
default:
ret = -1;
break;
}
skip_to_post_handle:
if (!ret && dev->extern_ops.post_msg_handle) {
uint32_t need_reply;
ret = (*dev->extern_ops.post_msg_handle)(
dev->vid, (void *)&msg, &need_reply);
if (ret < 0)
goto skip_to_reply;
if (need_reply)
send_vhost_reply(fd, &msg);
}
skip_to_reply:
if (unlock_required)
vhost_user_unlock_all_queue_pairs(dev);
if (msg.flags & VHOST_USER_NEED_REPLY) {
msg.payload.u64 = !!ret;
msg.size = sizeof(msg.payload.u64);
send_vhost_reply(fd, &msg);
} else if (ret) {
RTE_LOG(ERR, VHOST_CONFIG,
"vhost message handling failed.\n");
return -1;
}
if (!(dev->flags & VIRTIO_DEV_RUNNING) && virtio_is_ready(dev)) {
dev->flags |= VIRTIO_DEV_READY;
if (!(dev->flags & VIRTIO_DEV_RUNNING)) {
if (dev->dequeue_zero_copy) {
RTE_LOG(INFO, VHOST_CONFIG,
"dequeue zero copy is enabled\n");
}
if (dev->notify_ops->new_device(dev->vid) == 0)
dev->flags |= VIRTIO_DEV_RUNNING;
}
}
did = dev->vdpa_dev_id;
vdpa_dev = rte_vdpa_get_device(did);
if (vdpa_dev && virtio_is_ready(dev) &&
!(dev->flags & VIRTIO_DEV_VDPA_CONFIGURED) &&
msg.request.master == VHOST_USER_SET_VRING_ENABLE) {
if (vdpa_dev->ops->dev_conf)
vdpa_dev->ops->dev_conf(dev->vid);
dev->flags |= VIRTIO_DEV_VDPA_CONFIGURED;
if (vhost_user_host_notifier_ctrl(dev->vid, true) != 0) {
RTE_LOG(INFO, VHOST_CONFIG,
"(%d) software relay is used for vDPA, performance may be low.\n",
dev->vid);
}
}
return 0;
}
virtio告知DPDK共享内存的virtio queues内存地址
DPDK使用函数vhost_user_set_vring_addr将virtio的描述符、已用环和可用环地址转化为DPDK自身的地址空间。
dpdk-18.08/lib/librte_vhost/vhost_user.c
vhost_user_set_vring_addr()
/*
* The virtio device sends us the desc, used and avail ring addresses.
* This function then converts these to our address space.
*/
static int
vhost_user_set_vring_addr(struct virtio_net **pdev, VhostUserMsg *msg)
{
struct vhost_virtqueue *vq;
struct vhost_vring_addr *addr = &msg->payload.addr;
struct virtio_net *dev = *pdev;
if (dev->mem == NULL)
return -1;
/* addr->index refers to the queue index. The txq 1, rxq is 0. */
vq = dev->virtqueue[msg->payload.addr.index];
/*
* Rings addresses should not be interpreted as long as the ring is not
* started and enabled
*/
memcpy(&vq->ring_addrs, addr, sizeof(*addr));
vring_invalidate(dev, vq);
if (vq->enabled && (dev->features &
(1ULL << VHOST_USER_F_PROTOCOL_FEATURES))) {
dev = translate_ring_addresses(dev, msg->payload.addr.index);
if (!dev)
return -1;
*pdev = dev;
}
return 0;
}
只有在通过控制通道vhu套接口接收到VHOST_USER_SET_VRING_ADDR类型消息时，设置内存地址。
dpdk-18.08/lib/librte_vhost/vhost_user.c
vhost_user_msg_handler()
int
vhost_user_msg_handler(int vid, int fd)
{
struct virtio_net *dev;
struct VhostUserMsg msg;
struct rte_vdpa_device *vdpa_dev;
int did = -1;
int ret;
int unlock_required = 0;
uint32_t skip_master = 0;
dev = get_device(vid);
if (dev == NULL)
return -1;
if (!dev->notify_ops) {
dev->notify_ops = vhost_driver_callback_get(dev->ifname);
if (!dev->notify_ops) {
RTE_LOG(ERR, VHOST_CONFIG,
"failed to get callback ops for driver %s\n",
dev->ifname);
return -1;
}
}
ret = read_vhost_message(fd, &msg);
if (ret <= 0 || msg.request.master >= VHOST_USER_MAX) {
if (ret < 0)
RTE_LOG(ERR, VHOST_CONFIG,
"vhost read message failed\n");
else if (ret == 0)
RTE_LOG(INFO, VHOST_CONFIG,
"vhost peer closed\n");
else
RTE_LOG(ERR, VHOST_CONFIG,
"vhost read incorrect message\n");
return -1;
}
ret = 0;
if (msg.request.master != VHOST_USER_IOTLB_MSG)
RTE_LOG(INFO, VHOST_CONFIG, "read message %s\n",
vhost_message_str[msg.request.master]);
else
RTE_LOG(DEBUG, VHOST_CONFIG, "read message %s\n",
vhost_message_str[msg.request.master]);
ret = vhost_user_check_and_alloc_queue_pair(dev, &msg);
if (ret < 0) {
RTE_LOG(ERR, VHOST_CONFIG,
"failed to alloc queue\n");
return -1;
}
/*
* Note: we don't lock all queues on VHOST_USER_GET_VRING_BASE
* and VHOST_USER_RESET_OWNER, since it is sent when virtio stops
* and device is destroyed. destroy_device waits for queues to be
* inactive, so it is safe. Otherwise taking the access_lock
* would cause a dead lock.
*/
switch (msg.request.master) {
case VHOST_USER_SET_FEATURES:
case VHOST_USER_SET_PROTOCOL_FEATURES:
case VHOST_USER_SET_OWNER:
case VHOST_USER_SET_MEM_TABLE:
case VHOST_USER_SET_LOG_BASE:
case VHOST_USER_SET_LOG_FD:
case VHOST_USER_SET_VRING_NUM:
case VHOST_USER_SET_VRING_ADDR:
case VHOST_USER_SET_VRING_BASE:
case VHOST_USER_SET_VRING_KICK:
case VHOST_USER_SET_VRING_CALL:
case VHOST_USER_SET_VRING_ERR:
case VHOST_USER_SET_VRING_ENABLE:
case VHOST_USER_SEND_RARP:
case VHOST_USER_NET_SET_MTU:
case VHOST_USER_SET_SLAVE_REQ_FD:
vhost_user_lock_all_queue_pairs(dev);
unlock_required = 1;
break;
default:
break;
}
if (dev->extern_ops.pre_msg_handle) {
uint32_t need_reply;
ret = (*dev->extern_ops.pre_msg_handle)(dev->vid,
(void *)&msg, &need_reply, &skip_master);
if (ret < 0)
goto skip_to_reply;
if (need_reply)
send_vhost_reply(fd, &msg);
if (skip_master)
goto skip_to_post_handle;
}
switch (msg.request.master) {
case VHOST_USER_GET_FEATURES:
msg.payload.u64 = vhost_user_get_features(dev);
msg.size = sizeof(msg.payload.u64);
send_vhost_reply(fd, &msg);
break;
case VHOST_USER_SET_FEATURES:
ret = vhost_user_set_features(dev, msg.payload.u64);
break;
case VHOST_USER_GET_PROTOCOL_FEATURES:
vhost_user_get_protocol_features(dev, &msg);
send_vhost_reply(fd, &msg);
break;
case VHOST_USER_SET_PROTOCOL_FEATURES:
ret = vhost_user_set_protocol_features(dev, msg.payload.u64);
break;
case VHOST_USER_SET_OWNER:
ret = vhost_user_set_owner();
break;
case VHOST_USER_RESET_OWNER:
ret = vhost_user_reset_owner(dev);
break;
case VHOST_USER_SET_MEM_TABLE:
ret = vhost_user_set_mem_table(&dev, &msg);
break;
case VHOST_USER_SET_LOG_BASE:
ret = vhost_user_set_log_base(dev, &msg);
if (ret)
goto skip_to_reply;
/* it needs a reply */
msg.size = sizeof(msg.payload.u64);
send_vhost_reply(fd, &msg);
break;
case VHOST_USER_SET_LOG_FD:
close(msg.fds[0]);
RTE_LOG(INFO, VHOST_CONFIG, "not implemented.\n");
break;
case VHOST_USER_SET_VRING_NUM:
ret = vhost_user_set_vring_num(dev, &msg);
break;
case VHOST_USER_SET_VRING_ADDR:
ret = vhost_user_set_vring_addr(&dev, &msg);
break;
case VHOST_USER_SET_VRING_BASE:
ret = vhost_user_set_vring_base(dev, &msg);
break;
case VHOST_USER_GET_VRING_BASE:
ret = vhost_user_get_vring_base(dev, &msg);
if (ret)
goto skip_to_reply;
msg.size = sizeof(msg.payload.state);
send_vhost_reply(fd, &msg);
break;
case VHOST_USER_SET_VRING_KICK:
ret = vhost_user_set_vring_kick(&dev, &msg);
break;
case VHOST_USER_SET_VRING_CALL:
vhost_user_set_vring_call(dev, &msg);
break;
case VHOST_USER_SET_VRING_ERR:
if (!(msg.payload.u64 & VHOST_USER_VRING_NOFD_MASK))
close(msg.fds[0]);
RTE_LOG(INFO, VHOST_CONFIG, "not implemented\n");
break;
case VHOST_USER_GET_QUEUE_NUM:
msg.payload.u64 = (uint64_t)vhost_user_get_queue_num(dev);
msg.size = sizeof(msg.payload.u64);
send_vhost_reply(fd, &msg);
break;
case VHOST_USER_SET_VRING_ENABLE:
ret = vhost_user_set_vring_enable(dev, &msg);
break;
case VHOST_USER_SEND_RARP:
ret = vhost_user_send_rarp(dev, &msg);
break;
case VHOST_USER_NET_SET_MTU:
ret = vhost_user_net_set_mtu(dev, &msg);
break;
case VHOST_USER_SET_SLAVE_REQ_FD:
ret = vhost_user_set_req_fd(dev, &msg);
break;
case VHOST_USER_IOTLB_MSG:
ret = vhost_user_iotlb_msg(&dev, &msg);
break;
default:
ret = -1;
break;
}
skip_to_post_handle:
if (!ret && dev->extern_ops.post_msg_handle) {
uint32_t need_reply;
ret = (*dev->extern_ops.post_msg_handle)(
dev->vid, (void *)&msg, &need_reply);
if (ret < 0)
goto skip_to_reply;
if (need_reply)
send_vhost_reply(fd, &msg);
}
skip_to_reply:
if (unlock_required)
vhost_user_unlock_all_queue_pairs(dev);
if (msg.flags & VHOST_USER_NEED_REPLY) {
msg.payload.u64 = !!ret;
msg.size = sizeof(msg.payload.u64);
send_vhost_reply(fd, &msg);
} else if (ret) {
RTE_LOG(ERR, VHOST_CONFIG,
"vhost message handling failed.\n");
return -1;
}
if (!(dev->flags & VIRTIO_DEV_RUNNING) && virtio_is_ready(dev)) {
dev->flags |= VIRTIO_DEV_READY;
if (!(dev->flags & VIRTIO_DEV_RUNNING)) {
if (dev->dequeue_zero_copy) {
RTE_LOG(INFO, VHOST_CONFIG,
"dequeue zero copy is enabled\n");
}
if (dev->notify_ops->new_device(dev->vid) == 0)
dev->flags |= VIRTIO_DEV_RUNNING;
}
}
did = dev->vdpa_dev_id;
vdpa_dev = rte_vdpa_get_device(did);
if (vdpa_dev && virtio_is_ready(dev) &&
!(dev->flags & VIRTIO_DEV_VDPA_CONFIGURED) &&
msg.request.master == VHOST_USER_SET_VRING_ENABLE) {
if (vdpa_dev->ops->dev_conf)
vdpa_dev->ops->dev_conf(dev->vid);
dev->flags |= VIRTIO_DEV_VDPA_CONFIGURED;
if (vhost_user_host_notifier_ctrl(dev->vid, true) != 0) {
RTE_LOG(INFO, VHOST_CONFIG,
"(%d) software relay is used for vDPA, performance may be low.\n",
dev->vid);
}
}
return 0;
}
实际上，QEMU中有一个与DPDK的消息处理函数类型的处理函数。
qemu-3.0.0/contrib/libvhost-user/libvhost-user.c
vu_process_message()
static bool
vu_process_message(VuDev *dev, VhostUserMsg *vmsg)
{
int do_reply = 0;
/* Print out generic part of the request. */
DPRINT("================ Vhost user message ================\n");
DPRINT("Request: %s (%d)\n", vu_request_to_string(vmsg->request),
vmsg->request);
DPRINT("Flags: 0x%x\n", vmsg->flags);
DPRINT("Size: %d\n", vmsg->size);
if (vmsg->fd_num) {
int i;
DPRINT("Fds:");
for (i = 0; i < vmsg->fd_num; i++) {
DPRINT(" %d", vmsg->fds[i]);
}
DPRINT("\n");
}
if (dev->iface->process_msg &&
dev->iface->process_msg(dev, vmsg, &do_reply)) {
return do_reply;
}
switch (vmsg->request) {
case VHOST_USER_GET_FEATURES:
return vu_get_features_exec(dev, vmsg);
case VHOST_USER_SET_FEATURES:
return vu_set_features_exec(dev, vmsg);
case VHOST_USER_GET_PROTOCOL_FEATURES:
return vu_get_protocol_features_exec(dev, vmsg);
case VHOST_USER_SET_PROTOCOL_FEATURES:
return vu_set_protocol_features_exec(dev, vmsg);
case VHOST_USER_SET_OWNER:
return vu_set_owner_exec(dev, vmsg);
case VHOST_USER_RESET_OWNER:
return vu_reset_device_exec(dev, vmsg);
case VHOST_USER_SET_MEM_TABLE:
return vu_set_mem_table_exec(dev, vmsg);
case VHOST_USER_SET_LOG_BASE:
return vu_set_log_base_exec(dev, vmsg);
case VHOST_USER_SET_LOG_FD:
return vu_set_log_fd_exec(dev, vmsg);
case VHOST_USER_SET_VRING_NUM:
return vu_set_vring_num_exec(dev, vmsg);
case VHOST_USER_SET_VRING_ADDR:
return vu_set_vring_addr_exec(dev, vmsg);
case VHOST_USER_SET_VRING_BASE:
return vu_set_vring_base_exec(dev, vmsg);
case VHOST_USER_GET_VRING_BASE:
return vu_get_vring_base_exec(dev, vmsg);
case VHOST_USER_SET_VRING_KICK:
return vu_set_vring_kick_exec(dev, vmsg);
case VHOST_USER_SET_VRING_CALL:
return vu_set_vring_call_exec(dev, vmsg);
case VHOST_USER_SET_VRING_ERR:
return vu_set_vring_err_exec(dev, vmsg);
case VHOST_USER_GET_QUEUE_NUM:
return vu_get_queue_num_exec(dev, vmsg);
case VHOST_USER_SET_VRING_ENABLE:
return vu_set_vring_enable_exec(dev, vmsg);
case VHOST_USER_SET_SLAVE_REQ_FD:
return vu_set_slave_req_fd(dev, vmsg);
case VHOST_USER_GET_CONFIG:
return vu_get_config(dev, vmsg);
case VHOST_USER_SET_CONFIG:
return vu_set_config(dev, vmsg);
case VHOST_USER_NONE:
break;
case VHOST_USER_POSTCOPY_ADVISE:
return vu_set_postcopy_advise(dev, vmsg);
case VHOST_USER_POSTCOPY_LISTEN:
return vu_set_postcopy_listen(dev, vmsg);
case VHOST_USER_POSTCOPY_END:
return vu_set_postcopy_end(dev, vmsg);
default:
vmsg_close_fds(vmsg);
vu_panic(dev, "Unhandled request: %d", vmsg->request);
}
return false;
}
显然，QEMU中需要有函数通过UNIX套接口发送内存地址信息到DPDK中。
qemu-3.0.0/hw/virtio/vhost-user.c
vhost_user_set_vring_addr()
static int vhost_user_set_vring_addr(struct vhost_dev *dev,
struct vhost_vring_addr *addr)
{
VhostUserMsg msg = {
.hdr.request = VHOST_USER_SET_VRING_ADDR,
.hdr.flags = VHOST_USER_VERSION,
.payload.addr = *addr,
.hdr.size = sizeof(msg.payload.addr),
};
if (vhost_user_write(dev, &msg, NULL, 0) < 0) {
return -1;
}
return 0;
}
OVS DPDK发送数据包到客户机与发送丢包
OVS DPDK中向客户机发送数据包的函数为__netdev_dpdk_vhost_send，位于文件openvswitch-2.9.2/lib/netdev-dpdk.c。
rte_vhost_enqueue_burst()
OVS发送程序，在空间用完后，仍会尝试发送VHOST_ENQ_RETRY_NUM (默认8)次。如果在第一次尝试发送中，没有任何数据包发送成功（无数据包写入共享内存的环中），或者超过了VHOST_ENQ_RETRY_NUM宏限定的次数，剩余的数据包将被丢弃（批量发送最大可由32个数据包组成）。
uint16_t
rte_vhost_enqueue_burst(int vid, uint16_t queue_id,
struct rte_mbuf **pkts, uint16_t count)
{
struct virtio_net *dev = get_device(vid);
if (!dev)
return 0;
if (unlikely(!(dev->flags & VIRTIO_DEV_BUILTIN_VIRTIO_NET))) {
RTE_LOG(ERR, VHOST_DATA,
"(%d) %s: built-in vhost net backend is disabled.\n",
dev->vid, __func__);
return 0;
}
return virtio_dev_rx(dev, queue_id, pkts, count);
}
客户机接收中断处理
当OVS DPDK将新的数据包填入virtio环中时，有以下两种情形：
- 客户机没有在轮询其队列，需要告知其新数据包的到达；
- 客户机正在轮询队列，不需要告知新数据包的到达。
如果客户机使用Linux内核网络协议栈，内核中负责接收报文的NAPI机制混合使用中断和轮询模式。客户机OS开始工作在中断模式，一直到第一个中断进来。此时，CPU快速响应中断，调度内核软中断ksoftirqd线程处理，同时禁止后续中断。
ksoftirqd运行时，尝试处理尽可能多的数据包，但是不能超出netdev_budget限定的数量。如果队列中还有更多的数据包，ksoftirqd线程将重新调度自身，继续处理数据包，直到没有可用的数据包为止。此过程中一直是轮询处理，中断处于关闭状态。处理完数据包之后，ksoftirqd线程停止轮询，重新打开中断，等待下一个数据包到来的中断发生。
当客户机轮询时，CPU的caches高速缓存利用率非常高，避免了额外的延时。宿主机和客户机中合适的进程在运行，进一步降低了延时。另外的，宿主机发送中断IRQ到客户机时，需要对UNIX套接口写操作（系统调用），非常耗时，增加了额外的延时和开销。
作为NFV应用的一部分，客户机中运行DPDK的优势在于其PMD驱动处理流量的方式。PMD驱动工作在轮询模式，关闭了系统中断，OVS DPDK不再需要给客户机发送中断通知。OVS DPDK节省了写UNIX套接口的操作，不在需要执行内核系统调用。OVS DPDK得以一直运行在用户空间，客户机也可以省去处理由控制通道而来的中断，快速运行。
如果没有设置VRING_AVAIL_F_NO_INTERRUPT标志，表明客户机可以接收中断。到客户机的中断通过callfd和操作系统的eventfd组件实现。
客户机的OS可以启用或禁用中断。当客户机禁用virtio接口的中断时，virtio-net驱动通过宏VRING_AVAIL_F_NO_INTERRUPT实现。此宏在DPDK和QEMU中都有定义：
[root@overcloud-0 SOURCES]# grep VRING_AVAIL_F_NO_INTERRUPT -R | grep def
dpdk-18.08/drivers/net/virtio/virtio_ring.h:#define VRING_AVAIL_F_NO_INTERRUPT 1
dpdk-18.08/drivers/crypto/virtio/virtio_ring.h:#define VRING_AVAIL_F_NO_INTERRUPT 1
[root@overcloud-0 qemu]# grep AVAIL_F_NO_INTERRUPT -R -i | grep def
qemu-3.0.0/include/standard-headers/linux/virtio_ring.h:#define VRING_AVAIL_F_NO_INTERRUPT 1
qemu-3.0.0/roms/seabios/src/hw/virtio-ring.h:#define VRING_AVAIL_F_NO_INTERRUPT 1
qemu-3.0.0/roms/ipxe/src/include/ipxe/virtio-ring.h:#define VRING_AVAIL_F_NO_INTERRUPT 1
qemu-3.0.0/roms/seabios-hppa/src/hw/virtio-ring.h:#define VRING_AVAIL_F_NO_INTERRUPT 1
qemu-3.0.0/roms/SLOF/lib/libvirtio/virtio.h:#define VRING_AVAIL_F_NO_INTERRUPT 1
一旦vq->avail->flags中的VRING_AVAIL_F_NO_INTERRUPT标志位设置，指示DPDK不要发送中断到客户机。dpdk-18.08/lib/librte_vhost/vhost.h
vhost_vring_call_split()
static __rte_always_inline void
vhost_vring_call_split(struct virtio_net *dev, struct vhost_virtqueue *vq)
{
/* Flush used->idx update before we read avail->flags. */
rte_smp_mb();
/* Don't kick guest if we don't reach index specified by guest. */
if (dev->features & (1ULL << VIRTIO_RING_F_EVENT_IDX)) {
uint16_t old = vq->signalled_used;
uint16_t new = vq->last_used_idx;
VHOST_LOG_DEBUG(VHOST_DATA, "%s: used_event_idx=%d, old=%d, new=%d\n",
__func__,
vhost_used_event(vq),
old, new);
if (vhost_need_event(vhost_used_event(vq), new, old)
&& (vq->callfd >= 0)) {
vq->signalled_used = vq->last_used_idx;
eventfd_write(vq->callfd, (eventfd_t) 1);
}
} else {
/* Kick the guest if necessary. */
if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
&& (vq->callfd >= 0))
eventfd_write(vq->callfd, (eventfd_t)1);
}
}
如前所述，PMD驱动不需要执行写UNIX套接口的系统调用了。
OVS DPDK发送数据包到客户机-代码详情
__netdev_dpdk_vhost_send()
static void
__netdev_dpdk_vhost_send(struct netdev *netdev, int qid,
struct dp_packet **pkts, int cnt)
{
struct netdev_dpdk *dev = netdev_dpdk_cast(netdev);
struct rte_mbuf **cur_pkts = (struct rte_mbuf **) pkts;
unsigned int total_pkts = cnt;
unsigned int dropped = 0;
int i, retries = 0;
int vid = netdev_dpdk_get_vid(dev);
qid = dev->tx_q[qid % netdev->n_txq].map;
if (OVS_UNLIKELY(vid < 0 || !dev->vhost_reconfigured || qid < 0
|| !(dev->flags & NETDEV_UP))) {
rte_spinlock_lock(&dev->stats_lock);
dev->stats.tx_dropped+= cnt;
rte_spinlock_unlock(&dev->stats_lock);
goto out;
}
rte_spinlock_lock(&dev->tx_q[qid].tx_lock);
cnt = netdev_dpdk_filter_packet_len(dev, cur_pkts, cnt);
/* Check has QoS has been configured for the netdev */
cnt = netdev_dpdk_qos_run(dev, cur_pkts, cnt, true);
dropped = total_pkts - cnt;
do {
int vhost_qid = qid * VIRTIO_QNUM + VIRTIO_RXQ;
unsigned int tx_pkts;
tx_pkts = rte_vhost_enqueue_burst(vid, vhost_qid, cur_pkts, cnt);
if (OVS_LIKELY(tx_pkts)) {
/* Packets have been sent.*/
cnt -= tx_pkts;
/* Prepare for possible retry.*/
cur_pkts = &cur_pkts[tx_pkts];
} else {
/* No packets sent - do not retry.*/
break;
}
} while (cnt && (retries++ <= VHOST_ENQ_RETRY_NUM));
rte_spinlock_unlock(&dev->tx_q[qid].tx_lock);
rte_spinlock_lock(&dev->stats_lock);
netdev_dpdk_vhost_update_tx_counters(&dev->stats, pkts, total_pkts,
cnt + dropped);
rte_spinlock_unlock(&dev->stats_lock);
out:
for (i = 0; i < total_pkts - dropped; i++) {
dp_packet_delete(pkts[i]);
}
}
rte_vhost_enqueue_burst函数来自于DPDK的vhost库。
dpdk-18.08/lib/librte_vhost/rte_vhost.h
rte_vhost_enqueue_burst()
/**
* This function adds buffers to the virtio devices RX virtqueue. Buffers can
* be received from the physical port or from another virtual device. A packet
* count is returned to indicate the number of packets that were successfully
* added to the RX queue.
* @param vid
* vhost device ID
* @param queue_id
* virtio queue index in mq case
* @param pkts
* array to contain packets to be enqueued
* @param count
* packets num to be enqueued
* @return
* num of packets enqueued
*/
uint16_t rte_vhost_enqueue_burst(int vid, uint16_t queue_id,
struct rte_mbuf **pkts, uint16_t count);
dpdk-18.08/lib/librte_vhost/virtio_net.c
uint16_t
rte_vhost_enqueue_burst(int vid, uint16_t queue_id,
struct rte_mbuf **pkts, uint16_t count)
{
struct virtio_net *dev = get_device(vid);
if (!dev)
return 0;
if (unlikely(!(dev->flags & VIRTIO_DEV_BUILTIN_VIRTIO_NET))) {
RTE_LOG(ERR, VHOST_DATA,
"(%d) %s: built-in vhost net backend is disabled.\n",
dev->vid, __func__);
return 0;
}
return virtio_dev_rx(dev, queue_id, pkts, count);
}
virtio_dev_rx_packed函数和virtio_dev_rx_split函数都将数据包发送到客户机，并根据设置决定是否发送中断通知（write系统调用）。
dpdk-18.08/lib/librte_vhost/virtio_net.c
virtio_dev_rx()
static __rte_always_inline uint32_t
virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
struct rte_mbuf **pkts, uint32_t count)
{
struct vhost_virtqueue *vq;
uint32_t nb_tx = 0;
VHOST_LOG_DEBUG(VHOST_DATA, "(%d) %s\n", dev->vid, __func__);
if (unlikely(!is_valid_virt_queue_idx(queue_id, 0, dev->nr_vring))) {
RTE_LOG(ERR, VHOST_DATA, "(%d) %s: invalid virtqueue idx %d.\n",
dev->vid, __func__, queue_id);
return 0;
}
vq = dev->virtqueue[queue_id];
rte_spinlock_lock(&vq->access_lock);
if (unlikely(vq->enabled == 0))
goto out_access_unlock;
if (dev->features & (1ULL << VIRTIO_F_IOMMU_PLATFORM))
vhost_user_iotlb_rd_lock(vq);
if (unlikely(vq->access_ok == 0))
if (unlikely(vring_translate(dev, vq) < 0))
goto out;
count = RTE_MIN((uint32_t)MAX_PKT_BURST, count);
if (count == 0)
goto out;
if (vq_is_packed(dev))
nb_tx = virtio_dev_rx_packed(dev, vq, pkts, count);
else
nb_tx = virtio_dev_rx_split(dev, vq, pkts, count);
out:
if (dev->features & (1ULL << VIRTIO_F_IOMMU_PLATFORM))
vhost_user_iotlb_rd_unlock(vq);
out_access_unlock:
rte_spinlock_unlock(&vq->access_lock);
return nb_tx;
}
在virtio_dev_rx函数中：
count = RTE_MIN((uint32_t)MAX_PKT_BURST, count);
if (count == 0)
goto out;
发送数据包数量设置为MAX_PKT_BURST宏与空闲项数量（count）两者中的较小值。
最后，根据发送的数据包数量增加已用索引的值。
virtio_dev_rx_packed()
tatic __rte_always_inline uint32_t
virtio_dev_rx_packed(struct virtio_net *dev, struct vhost_virtqueue *vq,
struct rte_mbuf **pkts, uint32_t count)
{
uint32_t pkt_idx = 0;
uint16_t num_buffers;
struct buf_vector buf_vec[BUF_VECTOR_MAX];
for (pkt_idx = 0; pkt_idx < count; pkt_idx++) {
uint32_t pkt_len = pkts[pkt_idx]->pkt_len + dev->vhost_hlen;
uint16_t nr_vec = 0;
uint16_t nr_descs = 0;
if (unlikely(reserve_avail_buf_packed(dev, vq,
pkt_len, buf_vec, &nr_vec,
&num_buffers, &nr_descs) < 0)) {
VHOST_LOG_DEBUG(VHOST_DATA,
"(%d) failed to get enough desc from vring\n",
dev->vid);
vq->shadow_used_idx -= num_buffers;
break;
}
rte_prefetch0((void *)(uintptr_t)buf_vec[0].buf_addr);
VHOST_LOG_DEBUG(VHOST_DATA, "(%d) current index %d | end index %d\n",
dev->vid, vq->last_avail_idx,
vq->last_avail_idx + num_buffers);
if (copy_mbuf_to_desc(dev, vq, pkts[pkt_idx],
buf_vec, nr_vec,
num_buffers) < 0) {
vq->shadow_used_idx -= num_buffers;
break;
}
vq->last_avail_idx += nr_descs;
if (vq->last_avail_idx >= vq->size) {
vq->last_avail_idx -= vq->size;
vq->avail_wrap_counter ^= 1;
}
}
do_data_copy_enqueue(dev, vq);
if (likely(vq->shadow_used_idx)) {
flush_shadow_used_ring_packed(dev, vq);
vhost_vring_call_packed(dev, vq);
}
return pkt_idx;
}
virtio_dev_rx_split()
static __rte_always_inline uint32_t
virtio_dev_rx_split(struct virtio_net *dev, struct vhost_virtqueue *vq,
struct rte_mbuf **pkts, uint32_t count)
{
uint32_t pkt_idx = 0;
uint16_t num_buffers;
struct buf_vector buf_vec[BUF_VECTOR_MAX];
uint16_t avail_head;
rte_prefetch0(&vq->avail->ring[vq->last_avail_idx & (vq->size - 1)]);
avail_head = *((volatile uint16_t *)&vq->avail->idx);
for (pkt_idx = 0; pkt_idx < count; pkt_idx++) {
uint32_t pkt_len = pkts[pkt_idx]->pkt_len + dev->vhost_hlen;
uint16_t nr_vec = 0;
if (unlikely(reserve_avail_buf_split(dev, vq,
pkt_len, buf_vec, &num_buffers,
avail_head, &nr_vec) < 0)) {
VHOST_LOG_DEBUG(VHOST_DATA,
"(%d) failed to get enough desc from vring\n",
dev->vid);
vq->shadow_used_idx -= num_buffers;
break;
}
rte_prefetch0((void *)(uintptr_t)buf_vec[0].buf_addr);
VHOST_LOG_DEBUG(VHOST_DATA, "(%d) current index %d | end index %d\n",
dev->vid, vq->last_avail_idx,
vq->last_avail_idx + num_buffers);
if (copy_mbuf_to_desc(dev, vq, pkts[pkt_idx],
buf_vec, nr_vec,
num_buffers) < 0) {
vq->shadow_used_idx -= num_buffers;
break;
}
vq->last_avail_idx += num_buffers;
}
do_data_copy_enqueue(dev, vq);
if (likely(vq->shadow_used_idx)) {
flush_shadow_used_ring_split(dev, vq);
vhost_vring_call_split(dev, vq);
}
return pkt_idx;
}
数据包通过函数copy_mbuf_to_desc拷贝到客户机的内存中。最后，根据配置决定是否发送中断通知，参见函数vhost_vring_call_split和vhost_vring_call_packed。
vhost_vring_call_split()
static __rte_always_inline void
vhost_vring_call_split(struct virtio_net *dev, struct vhost_virtqueue *vq)
{
/* Flush used->idx update before we read avail->flags. */
rte_smp_mb();
/* Don't kick guest if we don't reach index specified by guest. */
if (dev->features & (1ULL << VIRTIO_RING_F_EVENT_IDX)) {
uint16_t old = vq->signalled_used;
uint16_t new = vq->last_used_idx;
VHOST_LOG_DEBUG(VHOST_DATA, "%s: used_event_idx=%d, old=%d, new=%d\n",
__func__,
vhost_used_event(vq),
old, new);
if (vhost_need_event(vhost_used_event(vq), new, old)
&& (vq->callfd >= 0)) {
vq->signalled_used = vq->last_used_idx;
eventfd_write(vq->callfd, (eventfd_t) 1);
}
} else {
/* Kick the guest if necessary. */
if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
&& (vq->callfd >= 0))
eventfd_write(vq->callfd, (eventfd_t)1);
}
}
vhost_vring_call_packed()
static __rte_always_inline void
vhost_vring_call_packed(struct virtio_net *dev, struct vhost_virtqueue *vq)
{
uint16_t old, new, off, off_wrap;
bool signalled_used_valid, kick = false;
/* Flush used desc update. */
rte_smp_mb();
if (!(dev->features & (1ULL << VIRTIO_RING_F_EVENT_IDX))) {
if (vq->driver_event->flags !=
VRING_EVENT_F_DISABLE)
kick = true;
goto kick;
}
old = vq->signalled_used;
new = vq->last_used_idx;
vq->signalled_used = new;
signalled_used_valid = vq->signalled_used_valid;
vq->signalled_used_valid = true;
if (vq->driver_event->flags != VRING_EVENT_F_DESC) {
if (vq->driver_event->flags != VRING_EVENT_F_DISABLE)
kick = true;
goto kick;
}
if (unlikely(!signalled_used_valid)) {
kick = true;
goto kick;
}
rte_smp_rmb();
off_wrap = vq->driver_event->off_wrap;
off = off_wrap & ~(1 << 15);
if (new <= old)
old -= vq->size;
if (vq->used_wrap_counter != off_wrap >> 15)
off -= vq->size;
if (vhost_need_event(off, new, old))
kick = true;
kick:
if (kick)
eventfd_write(vq->callfd, (eventfd_t)1);
}
static __rte_always_inline int
copy_desc_to_mbuf(struct virtio_net *dev, struct vhost_virtqueue *vq,
struct buf_vector *buf_vec, uint16_t nr_vec,
struct rte_mbuf *m, struct rte_mempool *mbuf_pool)
{
uint32_t buf_avail, buf_offset;
uint64_t buf_addr, buf_iova, buf_len;
uint32_t mbuf_avail, mbuf_offset;
uint32_t cpy_len;
struct rte_mbuf *cur = m, *prev = m;
struct virtio_net_hdr tmp_hdr;
struct virtio_net_hdr *hdr = NULL;
/* A counter to avoid desc dead loop chain */
uint16_t vec_idx = 0;
struct batch_copy_elem *batch_copy = vq->batch_copy_elems;
int error = 0;
buf_addr = buf_vec[vec_idx].buf_addr;
buf_iova = buf_vec[vec_idx].buf_iova;
buf_len = buf_vec[vec_idx].buf_len;
if (unlikely(buf_len < dev->vhost_hlen && nr_vec <= 1)) {
error = -1;
goto out;
}
if (likely(nr_vec > 1))
rte_prefetch0((void *)(uintptr_t)buf_vec[1].buf_addr);
if (virtio_net_with_host_offload(dev)) {
if (unlikely(buf_len < sizeof(struct virtio_net_hdr))) {
uint64_t len;
uint64_t remain = sizeof(struct virtio_net_hdr);
uint64_t src;
uint64_t dst = (uint64_t)(uintptr_t)&tmp_hdr;
uint16_t hdr_vec_idx = 0;
/*
* No luck, the virtio-net header doesn't fit
* in a contiguous virtual area.
*/
while (remain) {
len = RTE_MIN(remain,
buf_vec[hdr_vec_idx].buf_len);
src = buf_vec[hdr_vec_idx].buf_addr;
rte_memcpy((void *)(uintptr_t)dst,
(void *)(uintptr_t)src, len);
remain -= len;
dst += len;
hdr_vec_idx++;
}
hdr = &tmp_hdr;
} else {
hdr = (struct virtio_net_hdr *)((uintptr_t)buf_addr);
rte_prefetch0(hdr);
}
}
/*
* A virtio driver normally uses at least 2 desc buffers
* for Tx: the first for storing the header, and others
* for storing the data.
*/
if (unlikely(buf_len < dev->vhost_hlen)) {
buf_offset = dev->vhost_hlen - buf_len;
vec_idx++;
buf_addr = buf_vec[vec_idx].buf_addr;
buf_iova = buf_vec[vec_idx].buf_iova;
buf_len = buf_vec[vec_idx].buf_len;
buf_avail = buf_len - buf_offset;
} else if (buf_len == dev->vhost_hlen) {
if (unlikely(++vec_idx >= nr_vec))
goto out;
buf_addr = buf_vec[vec_idx].buf_addr;
buf_iova = buf_vec[vec_idx].buf_iova;
buf_len = buf_vec[vec_idx].buf_len;
buf_offset = 0;
buf_avail = buf_len;
} else {
buf_offset = dev->vhost_hlen;
buf_avail = buf_vec[vec_idx].buf_len - dev->vhost_hlen;
}
rte_prefetch0((void *)(uintptr_t)
(buf_addr + buf_offset));
PRINT_PACKET(dev,
(uintptr_t)(buf_addr + buf_offset),
(uint32_t)buf_avail, 0);
mbuf_offset = 0;
mbuf_avail = m->buf_len - RTE_PKTMBUF_HEADROOM;
while (1) {
uint64_t hpa;
cpy_len = RTE_MIN(buf_avail, mbuf_avail);
/*
* A desc buf might across two host physical pages that are
* not continuous. In such case (gpa_to_hpa returns 0), data
* will be copied even though zero copy is enabled.
*/
if (unlikely(dev->dequeue_zero_copy && (hpa = gpa_to_hpa(dev,
buf_iova + buf_offset, cpy_len)))) {
cur->data_len = cpy_len;
cur->data_off = 0;
cur->buf_addr =
(void *)(uintptr_t)(buf_addr + buf_offset);
cur->buf_iova = hpa;
/*
* In zero copy mode, one mbuf can only reference data
* for one or partial of one desc buff.
*/
mbuf_avail = cpy_len;
} else {
if (likely(cpy_len > MAX_BATCH_LEN ||
vq->batch_copy_nb_elems >= vq->size ||
(hdr && cur == m))) {
rte_memcpy(rte_pktmbuf_mtod_offset(cur, void *,
mbuf_offset),
(void *)((uintptr_t)(buf_addr +
buf_offset)),
cpy_len);
} else {
batch_copy[vq->batch_copy_nb_elems].dst =
rte_pktmbuf_mtod_offset(cur, void *,
mbuf_offset);
batch_copy[vq->batch_copy_nb_elems].src =
(void *)((uintptr_t)(buf_addr +
buf_offset));
batch_copy[vq->batch_copy_nb_elems].len =
cpy_len;
vq->batch_copy_nb_elems++;
}
}
mbuf_avail -= cpy_len;
mbuf_offset += cpy_len;
buf_avail -= cpy_len;
buf_offset += cpy_len;
/* This buf reaches to its end, get the next one */
if (buf_avail == 0) {
if (++vec_idx >= nr_vec)
break;
buf_addr = buf_vec[vec_idx].buf_addr;
buf_iova = buf_vec[vec_idx].buf_iova;
buf_len = buf_vec[vec_idx].buf_len;
/*
* Prefecth desc n + 1 buffer while
* desc n buffer is processed.
*/
if (vec_idx + 1 < nr_vec)
rte_prefetch0((void *)(uintptr_t)
buf_vec[vec_idx + 1].buf_addr);
buf_offset = 0;
buf_avail = buf_len;
PRINT_PACKET(dev, (uintptr_t)buf_addr,
(uint32_t)buf_avail, 0);
}
/*
* This mbuf reaches to its end, get a new one
* to hold more data.
*/
if (mbuf_avail == 0) {
cur = rte_pktmbuf_alloc(mbuf_pool);
if (unlikely(cur == NULL)) {
RTE_LOG(ERR, VHOST_DATA, "Failed to "
"allocate memory for mbuf.\n");
error = -1;
goto out;
}
if (unlikely(dev->dequeue_zero_copy))
rte_mbuf_refcnt_update(cur, 1);
prev->next = cur;
prev->data_len = mbuf_offset;
m->nb_segs += 1;
m->pkt_len += mbuf_offset;
prev = cur;
mbuf_offset = 0;
mbuf_avail = cur->buf_len - RTE_PKTMBUF_HEADROOM;
}
}
prev->data_len = mbuf_offset;
m->pkt_len += mbuf_offset;
if (hdr)
vhost_dequeue_offload(hdr, m);
out:
return error;
}
原文链接：
https://blog.csdn.net/sinat_20184565/article/details/83070894
https://access.redhat.com/solutions/3394851