xenbus.c

来自「xen 3.2.2 源码」· C语言 代码 · 共 664 行 · 第 1/2 页

/* 
 ****************************************************************************
 * (C) 2006 - Cambridge University
 ****************************************************************************
 *
 *        File: xenbus.c
 *      Author: Steven Smith ([e-mail]) 
 *     Changes: Grzegorz Milos ([e-mail])
 *     Changes: John D. Ramsdell
 *              
 *        Date: Jun 2006, chages Aug 2005
 * 
 * Environment: Xen Minimal OS
 * Description: Minimal implementation of xenbus
 *
 ****************************************************************************
 **/
#include <os.h>
#include <mm.h>
#include <traps.h>
#include <lib.h>
#include <xenbus.h>
#include <events.h>
#include <errno.h>
#include <sched.h>
#include <wait.h>
#include <xen/io/xs_wire.h>
#include <spinlock.h>
#include <xmalloc.h>

#define BUG_ON(x) do { \
    if (x) {printk("BUG at %s:%d\n", __FILE__, __LINE__); BUG(); } \
} while (0)

#define min(x,y) ({                       \
        typeof(x) tmpx = (x);                 \
        typeof(y) tmpy = (y);                 \
        tmpx < tmpy ? tmpx : tmpy;            \
        })

#ifdef XENBUS_DEBUG
#define DEBUG(_f, _a...) \
    printk("MINI_OS(file=xenbus.c, line=%d) " _f , __LINE__, ## _a)
#else
#define DEBUG(_f, _a...)    ((void)0)
#endif

static struct xenstore_domain_interface *xenstore_buf;
static DECLARE_WAIT_QUEUE_HEAD(xb_waitq);
static DECLARE_WAIT_QUEUE_HEAD(watch_queue);
struct xenbus_req_info 
{
    int in_use:1;
    struct wait_queue_head waitq;
    void *reply;
};

#define NR_REQS 32
static struct xenbus_req_info req_info[NR_REQS];

static void memcpy_from_ring(const void *Ring,
        void *Dest,
        int off,
        int len)
{
    int c1, c2;
    const char *ring = Ring;
    char *dest = Dest;
    c1 = min(len, XENSTORE_RING_SIZE - off);
    c2 = len - c1;
    memcpy(dest, ring + off, c1);
    memcpy(dest + c1, ring, c2);
}

void wait_for_watch(void)
{
    DEFINE_WAIT(w);
    add_waiter(w,watch_queue);
    schedule();
    remove_waiter(w);
    wake(current);
}

char* xenbus_wait_for_value(const char* path,const char* value)
{
    for(;;)
    {
        char *res, *msg;
        int r;

        msg = xenbus_read(XBT_NIL, path, &res);
        if(msg) return msg;

        r = strcmp(value,res);
        free(res);

        if(r==0) break;
        else wait_for_watch();
    }
    return NULL;
}


static void xenbus_thread_func(void *ign)
{
    struct xsd_sockmsg msg;
    unsigned prod = 0;

    for (;;) 
    {
        wait_event(xb_waitq, prod != xenstore_buf->rsp_prod);
        while (1) 
        {
            prod = xenstore_buf->rsp_prod;
            DEBUG("Rsp_cons %d, rsp_prod %d.\n", xenstore_buf->rsp_cons,
                    xenstore_buf->rsp_prod);
            if (xenstore_buf->rsp_prod - xenstore_buf->rsp_cons < sizeof(msg))
                break;
            rmb();
            memcpy_from_ring(xenstore_buf->rsp,
                    &msg,
                    MASK_XENSTORE_IDX(xenstore_buf->rsp_cons),
                    sizeof(msg));
            DEBUG("Msg len %d, %d avail, id %d.\n",
                    msg.len + sizeof(msg),
                    xenstore_buf->rsp_prod - xenstore_buf->rsp_cons,
                    msg.req_id);
            if (xenstore_buf->rsp_prod - xenstore_buf->rsp_cons <
                    sizeof(msg) + msg.len)
                break;

            DEBUG("Message is good.\n");

            if(msg.type == XS_WATCH_EVENT)
            {
                char* payload = (char*)malloc(sizeof(msg) + msg.len);
                char *path,*token;

                memcpy_from_ring(xenstore_buf->rsp,
                    payload,
                    MASK_XENSTORE_IDX(xenstore_buf->rsp_cons),
                    msg.len + sizeof(msg));

                path = payload + sizeof(msg);
                token = path + strlen(path) + 1;

                xenstore_buf->rsp_cons += msg.len + sizeof(msg);
                free(payload);
                wake_up(&watch_queue);
            }

            else
            {
                req_info[msg.req_id].reply = malloc(sizeof(msg) + msg.len);
                memcpy_from_ring(xenstore_buf->rsp,
                    req_info[msg.req_id].reply,
                    MASK_XENSTORE_IDX(xenstore_buf->rsp_cons),
                    msg.len + sizeof(msg));
                xenstore_buf->rsp_cons += msg.len + sizeof(msg);
                wake_up(&req_info[msg.req_id].waitq);
            }
        }
    }
}

static void xenbus_evtchn_handler(evtchn_port_t port, struct pt_regs *regs,
				  void *ign)
{
    wake_up(&xb_waitq);
}

static int nr_live_reqs;
static spinlock_t req_lock = SPIN_LOCK_UNLOCKED;
static DECLARE_WAIT_QUEUE_HEAD(req_wq);

/* Release a xenbus identifier */
static void release_xenbus_id(int id)
{
    BUG_ON(!req_info[id].in_use);
    spin_lock(&req_lock);
    req_info[id].in_use = 0;
    nr_live_reqs--;
    req_info[id].in_use = 0;
    if (nr_live_reqs == NR_REQS - 1)
        wake_up(&req_wq);
    spin_unlock(&req_lock);
}

/* Allocate an identifier for a xenbus request.  Blocks if none are
   available. */
static int allocate_xenbus_id(void)
{
    static int probe;
    int o_probe;

    while (1) 
    {
        spin_lock(&req_lock);
        if (nr_live_reqs < NR_REQS)
            break;
        spin_unlock(&req_lock);
        wait_event(req_wq, (nr_live_reqs < NR_REQS));
    }

    o_probe = probe;
    for (;;) 
    {
        if (!req_info[o_probe].in_use)
            break;
        o_probe = (o_probe + 1) % NR_REQS;
        BUG_ON(o_probe == probe);
    }
    nr_live_reqs++;
    req_info[o_probe].in_use = 1;
    probe = (o_probe + 1) % NR_REQS;
    spin_unlock(&req_lock);
    init_waitqueue_head(&req_info[o_probe].waitq);

    return o_probe;
}

/* Initialise xenbus. */
void init_xenbus(void)
{
    int err;
    printk("Initialising xenbus\n");
    DEBUG("init_xenbus called.\n");
    xenstore_buf = mfn_to_virt(start_info.store_mfn);
    create_thread("xenstore", xenbus_thread_func, NULL);
    DEBUG("buf at %p.\n", xenstore_buf);
    err = bind_evtchn(start_info.store_evtchn,
		      xenbus_evtchn_handler,
              NULL);
    DEBUG("xenbus on irq %d\n", err);
}

struct write_req {
    const void *data;
    unsigned len;
};

/* Send data to xenbus.  This can block.  All of the requests are seen
   by xenbus as if sent atomically.  The header is added
   automatically, using type %type, req_id %req_id, and trans_id
   %trans_id. */
static void xb_write(int type, int req_id, xenbus_transaction_t trans_id,
		     const struct write_req *req, int nr_reqs)
{
    XENSTORE_RING_IDX prod;
    int r;
    int len = 0;
    const struct write_req *cur_req;
    int req_off;
    int total_off;
    int this_chunk;
    struct xsd_sockmsg m = {.type = type, .req_id = req_id,
        .tx_id = trans_id };
    struct write_req header_req = { &m, sizeof(m) };

    for (r = 0; r < nr_reqs; r++)
        len += req[r].len;
    m.len = len;
    len += sizeof(m);

    cur_req = &header_req;

    BUG_ON(len > XENSTORE_RING_SIZE);
    /* Wait for the ring to drain to the point where we can send the
       message. */
    prod = xenstore_buf->req_prod;
    if (prod + len - xenstore_buf->req_cons > XENSTORE_RING_SIZE) 
    {
        /* Wait for there to be space on the ring */
        DEBUG("prod %d, len %d, cons %d, size %d; waiting.\n",
                prod, len, xenstore_buf->req_cons, XENSTORE_RING_SIZE);
        wait_event(xb_waitq,
                xenstore_buf->req_prod + len - xenstore_buf->req_cons <=
                XENSTORE_RING_SIZE);
        DEBUG("Back from wait.\n");
        prod = xenstore_buf->req_prod;
    }

    /* We're now guaranteed to be able to send the message without
       overflowing the ring.  Do so. */
    total_off = 0;
    req_off = 0;
    while (total_off < len) 
    {
        this_chunk = min(cur_req->len - req_off,
                XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(prod));
        memcpy((char *)xenstore_buf->req + MASK_XENSTORE_IDX(prod),
                (char *)cur_req->data + req_off, this_chunk);
        prod += this_chunk;
        req_off += this_chunk;
        total_off += this_chunk;
        if (req_off == cur_req->len) 
        {
            req_off = 0;
            if (cur_req == &header_req)
                cur_req = req;
            else
                cur_req++;
        }
    }

    DEBUG("Complete main loop of xb_write.\n");
    BUG_ON(req_off != 0);
    BUG_ON(total_off != len);
    BUG_ON(prod > xenstore_buf->req_cons + XENSTORE_RING_SIZE);

    /* Remote must see entire message before updating indexes */
    wmb();

    xenstore_buf->req_prod += len;

    /* Send evtchn to notify remote */
    notify_remote_via_evtchn(start_info.store_evtchn);
}

/* Send a mesasge to xenbus, in the same fashion as xb_write, and
   block waiting for a reply.  The reply is malloced and should be
   freed by the caller. */
static struct xsd_sockmsg *
xenbus_msg_reply(int type,
		 xenbus_transaction_t trans,
		 struct write_req *io,
		 int nr_reqs)
{
    int id;
    DEFINE_WAIT(w);
    struct xsd_sockmsg *rep;