From mboxrd@z Thu Jan  1 00:00:00 1970
From: Linda <lindaj@jma3.com>
Subject: Re: grant tables and driver handshaking
Date: Thu, 11 Jun 2015 06:32:08 -0600
Message-ID: <55797FC8.8050806@jma3.com>
References: <1429117327-6845-1-git-send-email-lindaj@jma3.com>
	<556F1C21.2010000@jma3.com> <5578E82B.1010601@jma3.com>
	<20150611104349.GI14606@zion.uk.xensource.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"; Format="flowed"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xen.org>
Received: from mail6.bemta14.messagelabs.com ([193.109.254.103])
	by lists.xen.org with esmtp (Exim 4.72)
	(envelope-from <lindaj@jma3.com>) id 1Z31ed-0001Ag-8j
	for xen-devel@lists.xenproject.org; Thu, 11 Jun 2015 12:32:19 +0000
In-Reply-To: <20150611104349.GI14606@zion.uk.xensource.com>
List-Unsubscribe: <http://lists.xen.org/cgi-bin/mailman/options/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xen.org>
List-Help: <mailto:xen-devel-request@lists.xen.org?subject=help>
List-Subscribe: <http://lists.xen.org/cgi-bin/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=subscribe>
Sender: xen-devel-bounces@lists.xen.org
Errors-To: xen-devel-bounces@lists.xen.org
To: Wei Liu <wei.liu2@citrix.com>
Cc: julien.grall@citrix.com, xen-devel@lists.xenproject.org, lars.kurth.xen@gmail.com
List-Id: xen-devel@lists.xenproject.org

On 6/11/2015 4:43 AM, Wei Liu wrote:
> On Wed, Jun 10, 2015 at 07:45:15PM -0600, Linda wrote:
>> Hello all,
>>      I will be writing a xen front and back-end pair for a 9p transport.  I
>> have two areas where I'm still a little more muddled than I'd like to be.
>>      Can anyone please recommend a good article on either grant tables or the
>> handshaking between the front and back-end drivers, or both?
> The handshake protocol needs to be designed by you. Generally speaking
> you need to at least advertise the event channel and grant table
> references. You also need to advertise other information that you
> identify as part of the handshake process.
OK.  That explains half of my muddle.

Here's the other half.  The wiki article on xenbus taks about the 
front-end registering with xenbus, before anything else happens. But in 
blkback, it looks like it too has to do some kind of setup with xenbus, 
too.

Since the backend is in DOM0, and is around longer than the DOMUs, this 
happens first.   It's that interaction that I'd like a little more text 
on.  If it exists.
>
> There is a wiki page on grant table
>
> http://wiki.xenproject.org/wiki/Grant_Table
Thanks.
>
> Wei.
>
>>      I have looked at the code, but could use more verbiage.
>> Thanks.
>>
>> Linda