From mboxrd@z Thu Jan  1 00:00:00 1970
From: Carsten Otte <cotte-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org>
Subject: Re: [PATCH RFC 3/3] virtio infrastructure: example
 block driver
Date: Thu, 31 May 2007 14:57:27 +0200
Message-ID: <465EC637.7020504@de.ibm.com>
References: <1180613947.11133.58.camel@localhost.localdomain>
	<1180614044.11133.61.camel@localhost.localdomain>
	<1180614091.11133.63.camel@localhost.localdomain>
Reply-To: carsteno-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Cc: Jimi Xenidis <jimix-aZOuKsOsJu3MbYB6QlFGEg@public.gmane.org>,
	Stephen Rothwell <sfr-3FnU+UHB4dNDw9hX6IcOSA@public.gmane.org>,
	Xen Mailing List <xen-devel-GuqFBffKawuULHF6PoxzQEEOCMrvLtNR@public.gmane.org>,
	"jmk-zzFmDc4TPjtKvsKVC3L/VUEOCMrvLtNR@public.gmane.org" <jmk-zzFmDc4TPjtKvsKVC3L/VUEOCMrvLtNR@public.gmane.org>,
	Herbert Xu <herbert-lOAM2aK0SrRLBo1qDEOMRrpzq4S04n8Q@public.gmane.org>,
	kvm-devel <kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org>,
	mschwid2-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org,
	virtualization <virtualization-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>,
	Christian Borntraeger <cborntra-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org>,
	Suzanne McIntosh <skranjac-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
To: Rusty Russell <rusty-8n+1lVoiYb80n/F98K4Iww@public.gmane.org>
Return-path: <kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org>
In-Reply-To: <1180614091.11133.63.camel-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@public.gmane.org>
List-Unsubscribe: <https://lists.sourceforge.net/lists/listinfo/kvm-devel>,
	<mailto:kvm-devel-request-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org?subject=unsubscribe>
List-Archive: <http://sourceforge.net/mailarchive/forum.php?forum_name=kvm-devel>
List-Post: <mailto:kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org>
List-Help: <mailto:kvm-devel-request-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org?subject=help>
List-Subscribe: <https://lists.sourceforge.net/lists/listinfo/kvm-devel>,
	<mailto:kvm-devel-request-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org?subject=subscribe>
Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
List-Id: kvm.vger.kernel.org

Rusty Russell wrote:
> Example block driver using virtio.
> 
> The block driver uses outbufs with sg[0] being the request information
> (struct virtio_blk_outhdr) with the type, sector and inbuf id.  For a
> write, the rest of the sg will contain the data to be written.
> 
> The first segment of the inbuf is a result code (struct
> virtio_blk_inhdr).  For a read, the rest of the sg points to the input
> buffer.
> 
> TODO:
> 	1) Ordered tag support.
Implementing a do_request function has quite a few disadvantages over 
hooking into q->make_request_fn. This way, we have the device plug 
(latency), request merging, and I/O scheduling inside the guest.
It seems preferable to do that in the host, especially when requests 
of multiple guests end up on the same physical media (shared access, 
or partitioned).

-------------------------------------------------------------------------
This SF.net email is sponsored by DB2 Express
Download DB2 Express C - the FREE version of DB2 express and take
control of your XML. No limits. Just data. Click to get it now.
http://sourceforge.net/powerbar/db2/