From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43)
	id 1NwyaT-0003a6-KA
	for qemu-devel@nongnu.org; Wed, 31 Mar 2010 10:08:05 -0400
Received: from [140.186.70.92] (port=38601 helo=eggs.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1NwyaQ-0003OE-3x
	for qemu-devel@nongnu.org; Wed, 31 Mar 2010 10:08:05 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69)
	(envelope-from <amit.shah@redhat.com>) id 1NwyaE-0005kD-UO
	for qemu-devel@nongnu.org; Wed, 31 Mar 2010 10:07:56 -0400
Received: from mx1.redhat.com ([209.132.183.28]:15279)
	by eggs.gnu.org with esmtp (Exim 4.69)
	(envelope-from <amit.shah@redhat.com>) id 1NwyaE-0005i5-8j
	for qemu-devel@nongnu.org; Wed, 31 Mar 2010 10:07:50 -0400
Received: from int-mx04.intmail.prod.int.phx2.redhat.com
	(int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.17])
	by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id o2VE7eaP028018
	(version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK)
	for <qemu-devel@nongnu.org>; Wed, 31 Mar 2010 10:07:40 -0400
Date: Wed, 31 Mar 2010 19:36:12 +0530
From: Amit Shah <amit.shah@redhat.com>
Subject: Re: [Qemu-devel] [PATCH 15/17] virtio-serial: Apps should consume
	all data that guest sends out / Fix virtio api abuse
Message-ID: <20100331140612.GA18283@amit-x200.redhat.com>
References: <1270020848-15526-8-git-send-email-amit.shah@redhat.com>
	<1270020848-15526-9-git-send-email-amit.shah@redhat.com>
	<1270020848-15526-10-git-send-email-amit.shah@redhat.com>
	<1270020848-15526-11-git-send-email-amit.shah@redhat.com>
	<1270020848-15526-12-git-send-email-amit.shah@redhat.com>
	<1270020848-15526-13-git-send-email-amit.shah@redhat.com>
	<1270020848-15526-14-git-send-email-amit.shah@redhat.com>
	<1270020848-15526-15-git-send-email-amit.shah@redhat.com>
	<1270020848-15526-16-git-send-email-amit.shah@redhat.com>
	<4BB353F7.10207@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <4BB353F7.10207@redhat.com>
List-Id: qemu-devel.nongnu.org
List-Unsubscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.gnu.org/pipermail/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Gerd Hoffmann <kraxel@redhat.com>
Cc: Juan Quintela <quintela@redhat.com>, qemu list <qemu-devel@nongnu.org>, "Michael S. Tsirkin" <mst@redhat.com>

On (Wed) Mar 31 2010 [15:53:59], Gerd Hoffmann wrote:
>>   /* Callback function that's called when the guest sends us data */
>> -static size_t flush_buf(VirtIOSerialPort *port, const uint8_t *buf, size_t len)
>> +static void flush_buf(VirtIOSerialPort *port, const uint8_t *buf, size_t len)
>>   {
>>       VirtConsole *vcon = DO_UPCAST(VirtConsole, port, port);
>> -    ssize_t ret;
>>
>> -    ret = qemu_chr_write(vcon->chr, buf, len);
>> -
>> -    return ret<  0 ? 0 : ret;
>> +    qemu_chr_write(vcon->chr, buf, len);
>>   }
>
> Ok, so we loose data in case qemu_chr_write wasn't able to write out all  
> data?  Nice opportunity to show flow control in action here ;)
>
> On failed+partial writes just put the remaining data into a buffer and  
> throttle the port until all buffered data has been successfully written  
> to the chardev.
>
> Incremental patch is fine to avoid the chicken-egg issue (throttling is  
> added by patch #17).

Yes, that's what I intend to do in a later patch (series).

		Amit