libxenctrl

Ø         简介

libxenctrl是一个C库，它提供了一些简单易用的API，使用户程序可以方便的和Hypervisor进行通信。

它的工作原理很简单，封装了dom0中的/proc/xen/privcmd，/dev/xen/evtchn以及/dev/xen/gntdev提供的IOCTL接口。

 

Ø         编程步骤：

²         /proc/xen/privcmd

1.         xc_interface_open()

打开/proc/xen/privcmd，获得文件描述符。

2.         xc_sysctl()

填充xen_sysctl结构体，发送ioctl请求。

3.         xc_interface_close()

关闭1中打开的文件描述符。

²         /dev/xen/evtchn

1.         xc_evtchn_open

2.         xc_evtchn_notify等函数

evtchn的操作比较简单，不需要填充结构体，一般指明远程Dom id，port即可

3.         xc_evtchn_close

²         /dev/xen/gntdev

1.         xc_gnttab_open

2.         xc_gnttab_map_grant_ref等

3.         xc_gnttab_close

 

 

Ø         编程示例

以/proc/xen/privcmd提供的接口为例，节选自tools/xenmon/setmask.c

 

int main(int argc, char * argv[])

{

    struct xen_sysctl sysctl;

    int ret;

 

    int xc_handle = xc_interface_open();

    sysctl.cmd = XEN_SYSCTL_tbuf_op;        // 由cmd决定sysctl(struct xen_sysctl)中的union

    sysctl.interface_version = XEN_SYSCTL_INTERFACE_VERSION;

    sysctl.u.tbuf_op.cmd  = XEN_SYSCTL_TBUFOP_get_info;

    ret = xc_sysctl(xc_handle, &sysctl);

    if ( ret != 0 )

    {

        perror("Failure to get event mask from Xen");

        exit(1);

    }

    else

    {

        printf("Current event mask: 0x%.8x\n", sysctl.u.tbuf_op.evt_mask);

    }

 

...snip...

 

    xc_interface_close(xc_handle);

    return 0;

}

 

²         XEN_SYSCTL Command (IOCTL的主命令为IOCTL_PRIVCMD_HYPERCALL)

 

No.	Command	Comment	Struct
1	XEN_SYSCTL_readconsole	Read console content from Xen buffer ring.	xen_sysctl_readconsole
2	XEN_SYSCTL_tbuf_op	Get trace buffers machine base address	xen_sysctl_tbuf_op
3	XEN_SYSCTL_physinfo	Get physical information about the host machine	xen_sysctl_physinfo
4	XEN_SYSCTL_sched_id	Get the ID of the current scheduler.	xen_sysctl_sched_id
5	XEN_SYSCTL_perfc_op	Interface for controlling Xen software performance counters.	xen_sysctl_perfc_op
6	XEN_SYSCTL_getdomaininfolist	-	xen_sysctl_getdomaininfolist
7	XEN_SYSCTL_debug_keys	Inject debug keys into Xen.	xen_sysctl_debug_keys
8	XEN_SYSCTL_getcpuinfo	Get physical CPU information.	xen_sysctl_getcpuinfo
9	XEN_SYSCTL_availheap	-	xen_sysctl_availheap
10	XEN_SYSCTL_get_pmstat	-	xen_sysctl_get_pmstat
11	XEN_SYSCTL_cpu_hotplug	-	xen_sysctl_cpu_hotplug
12	XEN_SYSCTL_pm_op	Get/set xen power management, include cpufreq governors and related parameters	xen_sysctl_page_offline_op
13	-	-	-
14	XEN_SYSCTL_page_offline_op	-	xen_sysctl_page_offline_op
15	XEN_SYSCTL_lockprof_op	-	xen_sysctl_lockprof_op

 

struct xen_sysctl {

    uint32_t cmd;

    uint32_t interface_version; /* XEN_SYSCTL_INTERFACE_VERSION */

    union {

        struct xen_sysctl_readconsole       readconsole;

        struct xen_sysctl_tbuf_op           tbuf_op;

        struct xen_sysctl_physinfo          physinfo;

        struct xen_sysctl_sched_id          sched_id;

        struct xen_sysctl_perfc_op          perfc_op;

        struct xen_sysctl_getdomaininfolist getdomaininfolist;

        struct xen_sysctl_debug_keys        debug_keys;

        struct xen_sysctl_getcpuinfo        getcpuinfo;

        struct xen_sysctl_availheap         availheap;

        struct xen_sysctl_get_pmstat        get_pmstat;

        struct xen_sysctl_cpu_hotplug       cpu_hotplug;

        struct xen_sysctl_pm_op             pm_op;

        struct xen_sysctl_page_offline_op   page_offline;

        struct xen_sysctl_lockprof_op       lockprof_op;

        uint8_t                             pad[128];

    } u;

};

typedef struct xen_sysctl xen_sysctl_t;