答复: [Xen-devel] Re: [PATCH] libxl: fix xenstore connection when run in domU

["Jun Zhu (Intern)" <Jun.Zhu@xxxxxxxxxx>]

In pvops, in the function  xenbus_file_write of file drivers/xen/xenfs/xenbus.c.
In the switch, there is no XS_INTRODUCE which is used to create a new domain.
These commands are eliminated here, since in default, a Domu cannot use these 
commands. 

static ssize_t xenbus_file_write(struct file *filp,
                                const char __user *ubuf,
                                size_t len, loff_t *ppos)
{
        struct xenbus_file_priv *u = filp->private_data;
        uint32_t msg_type;
        int rc = len;
        int ret;
        LIST_HEAD(staging_q);

        /*
         * We're expecting usermode to be writing properly formed
         * xenbus messages.  If they write an incomplete message we
         * buffer it up.  Once it is complete, we act on it.
         */

        /*
         * Make sure concurrent writers can't stomp all over each
         * other's messages and make a mess of our partial message
         * buffer.  We don't make any attemppt to stop multiple
         * writers from making a mess of each other's incomplete
         * messages; we're just trying to guarantee our own internal
         * consistency and make sure that single writes are handled
         * atomically.
         */
        mutex_lock(&u->msgbuffer_mutex);

        /* Get this out of the way early to avoid confusion */
        if (len == 0)
                goto out;

        /* Can't write a xenbus message larger we can buffer */
        if ((len + u->len) > sizeof(u->u.buffer)) {
                /* On error, dump existing buffer */
                u->len = 0;
                rc = -EINVAL;
                goto out;
        }

        ret = copy_from_user(u->u.buffer + u->len, ubuf, len);

        if (ret == len) {
                rc = -EFAULT;
                goto out;
        }

        /* Deal with a partial copy. */
        len -= ret;
        rc = len;

        u->len += len;

        /* Return if we haven't got a full message yet */
        if (u->len < sizeof(u->u.msg))
                goto out;       /* not even the header yet */

        /* If we're expecting a message that's larger than we can
           possibly send, dump what we have and return an error. */
        if ((sizeof(u->u.msg) + u->u.msg.len) > sizeof(u->u.buffer)) {
                rc = -E2BIG;
                u->len = 0;
                goto out;
        }

        if (u->len < (sizeof(u->u.msg) + u->u.msg.len))
                goto out;       /* incomplete data portion */

        /*
         * OK, now we have a complete message.  Do something with it.
         */

        msg_type = u->u.msg.type;

        switch (msg_type) {
        case XS_TRANSACTION_START:
        case XS_TRANSACTION_END:
        case XS_DIRECTORY:
        case XS_READ:
        case XS_GET_PERMS:
        case XS_RELEASE:
        case XS_GET_DOMAIN_PATH:
        case XS_WRITE:
        case XS_MKDIR:
        case XS_RM:
        case XS_SET_PERMS:
                /* Send out a transaction */
                ret = xenbus_write_transaction(msg_type, u);
                break;

        case XS_WATCH:
        case XS_UNWATCH:
                /* (Un)Ask for some path to be watched for changes */
                ret = xenbus_write_watch(msg_type, u);
                break;

        default:
                ret = -EINVAL;
                break;
        }
        if (ret != 0)
                rc = ret;

        /* Buffered message consumed */
        u->len = 0;

 out:
        mutex_unlock(&u->msgbuffer_mutex);
        return rc;
}


Jun Zhu
Citrix Systems UK
________________________________________
发件人: Patrick Colp [pjcolp@xxxxxxxxx]
发送时间: 2010年8月31日 下午 1:51
收件人: Ian Campbell
抄送: Jun Zhu (Intern); Tim Deegan; dgdegra@xxxxxxxxxxxxx; 
xen-devel@xxxxxxxxxxxxxxxxxxx
主题: Re: [Xen-devel] Re: [PATCH] libxl: fix xenstore connection when run in domU

Which XenBus driver is this? In Linux? I've certainly had no issues
running a Mini-OS XenStore stubdom (at least not in regards to missing
things like XS_INTRODUCE).


Patrick


On 31 August 2010 03:44, Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx> wrote:
> On Tue, 2010-08-31 at 11:32 +0100, Jun Zhu (Intern) wrote:
>>
>> If xenstore runs in a seperate domain, it must use xenbus dev to
>> communicate. If so, the xenstore commands in Xenbus driver are not
>> complete. For example, it does not contain XS_INTRODUCE now.
>
> IIRC Diego's original xenstore-stubdom patch series from way back when
> (posted to the list by Diego and again later by Alex Zeffertt) included
> patches to the kernel side xenbus driver to resolve issues like this.
>
> Ian.
>
>
>

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