From mboxrd@z Thu Jan  1 00:00:00 1970
From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Subject: Re: [PATCH 0/3] virtio: Clean up scatterlists and use the DMA API
Date: Wed, 27 Aug 2014 13:27:16 -0400
Message-ID: <20140827172716.GA5379@laptop.dumpdata.com>
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To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: linux-s390 <linux-s390@vger.kernel.org>, "Michael S. Tsirkin" <mst@redhat.com>, Linux Virtualization <virtualization@lists.linux-foundation.org>, linux390@de.ibm.com, Andy Lutomirski <luto@amacapital.net>, virtio-dev@lists.oasis-open.org
List-ID: <linux-s390.vger.kernel.org>

On Wed, Aug 27, 2014 at 07:46:46AM +0100, Stefan Hajnoczi wrote:
> On Tue, Aug 26, 2014 at 10:16 PM, Andy Lutomirski <luto@amacapital.net> wrote:
> > There are two outstanding issues.  virtio_net warns if DMA debugging
> > is on because it does DMA from the stack.  (The warning is correct.)
> > This also is likely to do something unpleasant to s390.
> > (Maintainers are cc'd -- I don't know what to do about it.)
> 
> This changes the semantics of vring and breaks existing guests when
> bus address != physical address.

Isn't that what this is suppose to fix? Right now the semantics of the
vring is that bus address == physical address.

> 
> Can you use a transport feature bit to indicate that bus addresses are
> used?  That way both approaches can be supported.
> 
> Please also update the virtio specification:
> https://tools.oasis-open.org/version-control/browse/wsvn/virtio/
> 
> Stefan