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Subject: Re: [Xen-devel] [PATCH 1/3] xen/pv-on-hvm kexec: add xs_introduce
 to shutdown watches from old kernel
From: Ian Campbell <Ian.Campbell@citrix.com>
To: Olaf Hering <olaf@aepfle.de>
CC: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "Jeremy Fitzhardinge" <jeremy@goop.org>,
        Konrad <konrad.wilk@oracle.com>,
        "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>
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	 <20110804162054.096018606@aepfle.de>
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Date: Tue, 9 Aug 2011 10:15:18 +0100
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> Index: linux-3.0/drivers/xen/xenbus/xenbus_xs.c
> ===================================================================
> --- linux-3.0.orig/drivers/xen/xenbus/xenbus_xs.c
> +++ linux-3.0/drivers/xen/xenbus/xenbus_xs.c
> @@ -620,6 +620,20 @@ static struct xenbus_watch *find_watch(c
>  	return NULL;
>  }
>  
> +static int xs_introduce(const char *domid, const char *mfn, const char *port)
> +{
> +	struct kvec iov[3];
> +
> +	iov[0].iov_base = (char *)domid;
> +	iov[0].iov_len = strlen(domid) + 1;
> +	iov[1].iov_base = (char *)mfn;
> +	iov[1].iov_len = strlen(mfn) + 1;
> +	iov[2].iov_base = (char *)port;
> +	iov[2].iov_len = strlen(port) + 1;
> +
> +	return xs_error(xs_talkv(XBT_NIL, XS_INTRODUCE, iov,
> +				 ARRAY_SIZE(iov), NULL));

What should we do if this fails?

> +}
>  /* Register callback to watch this node. */
>  int register_xenbus_watch(struct xenbus_watch *watch)
>  {
> @@ -867,10 +881,11 @@ static int xenbus_thread(void *unused)
>  	return 0;
>  }
>  
> -int xs_init(void)
> +int xs_init(unsigned long xen_store_mfn)
>  {
>  	int err;
>  	struct task_struct *task;
> +	char domid[12], mfn[24], port[24];
>  
>  	INIT_LIST_HEAD(&xs_state.reply_list);
>  	spin_lock_init(&xs_state.reply_lock);
> @@ -897,5 +912,15 @@ int xs_init(void)
>  	if (IS_ERR(task))
>  		return PTR_ERR(task);
>  
> +	snprintf(domid, sizeof(domid), "%u", DOMID_SELF);
> +	snprintf(mfn, sizeof(mfn), "%lu", xen_store_mfn);
> +	snprintf(port, sizeof(port), "%d", xen_store_evtchn);

These can be within the if, or better within the xs_introduce function
itself.

> +	if (xen_hvm_domain()) {
> +		/* shutdown watches for kexec boot */
> +		err = xs_introduce(domid, mfn, port);
> +		if (err)
> +			printk(KERN_WARNING "xs_introduce failed: %d\n", err);
> +	}
> +
>  	return 0;
>  }
> 
> 
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