From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:50978)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <mst@redhat.com>) id 1WzpSq-0006Kq-DF
	for qemu-devel@nongnu.org; Wed, 25 Jun 2014 11:50:30 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <mst@redhat.com>) id 1WzpSk-0007CY-4o
	for qemu-devel@nongnu.org; Wed, 25 Jun 2014 11:50:23 -0400
Received: from mx1.redhat.com ([209.132.183.28]:59329)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <mst@redhat.com>) id 1WzpSj-0007CN-SA
	for qemu-devel@nongnu.org; Wed, 25 Jun 2014 11:50:18 -0400
Date: Wed, 25 Jun 2014 18:50:38 +0300
From: "Michael S. Tsirkin" <mst@redhat.com>
Message-ID: <20140625155038.GG15720@redhat.com>
References: <A459CE38-2929-47A2-8683-8D7EAF0325C0@cisco.com>
	<20140625135207.GC14578@redhat.com>
	<AC6F8B59-DE04-4F32-8D22-5B348680AA75@cisco.com>
	<CADDJ2=N2vxsy7tgvu0UWuzwBLZQ=KVh_KxACk67ZPjjJNRT71Q@mail.gmail.com>
	<A8A6A4DC-E474-45BB-A583-F73405F91F34@cisco.com>
	<20140625142704.GC15277@redhat.com>
	<7B7FFD16-82ED-4D0E-8B83-A6448DC9A344@cisco.com>
	<20140625152936.GB15720@redhat.com>
	<F6EF1C72-B3B7-4DAA-8CDB-0BD591E9E64D@cisco.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <F6EF1C72-B3B7-4DAA-8CDB-0BD591E9E64D@cisco.com>
Content-Transfer-Encoding: quoted-printable
Subject: Re: [Qemu-devel] vhost-user: broken mem regions
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: "Damjan Marion (damarion)" <damarion@cisco.com>
Cc: "pbonzini@redhat.com" <pbonzini@redhat.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, Nikolay Nikolaev <n.nikolaev@virtualopensystems.com>

On Wed, Jun 25, 2014 at 03:46:04PM +0000, Damjan Marion (damarion) wrote:
>=20
> On 25 Jun 2014, at 17:29, Michael S. Tsirkin <mst@redhat.com> wrote:
>=20
> > On Wed, Jun 25, 2014 at 02:57:52PM +0000, Damjan Marion (damarion) wr=
ote:
> >>=20
> >> On 25 Jun 2014, at 16:27, Michael S. Tsirkin <mst@redhat.com> wrote:
> >>=20
> >>> On Wed, Jun 25, 2014 at 02:20:56PM +0000, Damjan Marion (damarion) =
wrote:
> >>>>=20
> >>>> On 25 Jun 2014, at 16:13, Nikolay Nikolaev <n.nikolaev@virtualopen=
systems.com> wrote:
> >>>>=20
> >>>>>>> - it will require changes on the user side also
> >>>>>>=20
> >>>>>> why would it?
> >>>>>> format seems unchanged, right?
> >>>>>=20
> >>>>> yes, but it will happen that multiple regions have same FD so cal=
l to mmap()
> >>>>> should look different, I=E2=80=99m still playing with this on use=
r side...
> >>>>> but then you shoudl somehow accumulate the sizes and send just a =
single fd, something along these lines.=20
> >>>>=20
> >>>> Yes, so I=E2=80=99m not very happy with that approach and looking =
if there is better proposal,=20
> >>>> or at least wider agreement how to address this issue.
> >>>>=20
> >>>> Damjan
> >>>=20
> >>> still not sure what the issue is ...
> >>>=20
> >>=20
> >> No issue, just additional logic is needed on user side to calculate =
total size of shared regions and call mmap() once per FD.
> >>=20
> >> Agree?
> >=20
> > why not just call it multiple times? AFAIK linux handles this just fi=
ne.
>=20
> I need to specify size when calling mmap(), so i need to run trough all=
 regions and sum sizes before calling mmap().

You can map same file in many places.
Just call mmap many times with offsets.

--=20
MST