From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43)
	id 1L6vBx-0007Rj-Np
	for qemu-devel@nongnu.org; Sun, 30 Nov 2008 17:55:05 -0500
Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43)
	id 1L6vBv-0007Pi-Ov
	for qemu-devel@nongnu.org; Sun, 30 Nov 2008 17:55:05 -0500
Received: from [199.232.76.173] (port=37536 helo=monty-python.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1L6vBv-0007PW-KJ
	for qemu-devel@nongnu.org; Sun, 30 Nov 2008 17:55:03 -0500
Received: from an-out-0708.google.com ([209.85.132.244]:3279)
	by monty-python.gnu.org with esmtp (Exim 4.60)
	(envelope-from <anthony@codemonkey.ws>) id 1L6vBv-00084J-5h
	for qemu-devel@nongnu.org; Sun, 30 Nov 2008 17:55:03 -0500
Received: by an-out-0708.google.com with SMTP id c38so736757ana.37
	for <qemu-devel@nongnu.org>; Sun, 30 Nov 2008 14:55:02 -0800 (PST)
Message-ID: <493319C3.2080405@codemonkey.ws>
Date: Sun, 30 Nov 2008 16:54:59 -0600
From: Anthony Liguori <anthony@codemonkey.ws>
MIME-Version: 1.0
Subject: Re: [Qemu-devel] Re: [RFC 1/1] pci-dma-api-v2
References: <20081127123538.GC10348@random.random>	<f43fc5580811271114u7ecc3277kc7518fb7dbf9b4c0@mail.gmail.com>	<20081128015602.GA31011@random.random>	<f43fc5580811280959k3410e62eq7a2a46417b438b64@mail.gmail.com>	<20081128185001.GD31011@random.random>	<20081130174133.GC32172@random.random>	<f43fc5580811301036r19c15898me62cc07b16da71ba@mail.gmail.com>	<20081130190408.GE32172@random.random>	<f43fc5580811301111w5e1d7b77wf83825c2c2b826d3@mail.gmail.com>	<20081130192000.GF32172@random.random>
	<f43fc5580811301336o15213dfcl6b3225f2768d7cd3@mail.gmail.com>
In-Reply-To: <f43fc5580811301336o15213dfcl6b3225f2768d7cd3@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Reply-To: qemu-devel@nongnu.org
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: qemu-devel@nongnu.org
Cc: Andrea Arcangeli <aarcange@redhat.com>

Blue Swirl wrote:
> On 11/30/08, Andrea Arcangeli <aarcange@redhat.com> wrote:
>   
>> On Sun, Nov 30, 2008 at 09:11:28PM +0200, Blue Swirl wrote:
>>  > Yes, this version (attached) works.
>>
>>
>> Ok great! ;)
>>     
>
> This looks promising. Maybe the previous attempts tried to solve
> several problems at once, like the complex address translation schemes
> I have in mind, in addition to the basic zero-copy DMA transfer.This
> version leaves the DMA address translation to the caller and operates
> using physical memory addresses. Another way would be to use directly
> host pointers.
>   

I'm happy to separate address translation from just zero-copy IO.  I 
agree that a lot of the complexity is introduced trying to solve everything.

For me, just extending the BlockDriver API is a problem.  I'd like to 
see the API properly structured around a single vector API.  This is 
independent of zero copy.

I also think that in the very least, a DMA must be encapsulated in a 
structure, that has functions to pin()/unpin() that generate bounce 
buffers as necessary.

I think it's probably a good idea to separate a basic DMA api from a PCI 
DMA api.

Regards,

Anthony Liguori