From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [RFC PATCH 0/4] vhost_net: support for cross endian guests
Date: Mon, 3 Nov 2014 18:23:49 +0200
Message-ID: <20141103162349.GB24877@redhat.com>
References: <1414571925-16918-1-git-send-email-clg@fr.ibm.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: QUOTED-PRINTABLE
Cc: kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, agraf@suse.de,
	paulus@samba.org, gkurz@linux.vnet.ibm.com.patch, aik@ozlabs.ru
To: =?iso-8859-1?Q?C=E9dric?= Le Goater <clg@fr.ibm.com>
Return-path: <kvm-ppc-owner@vger.kernel.org>
Content-Disposition: inline
In-Reply-To: <1414571925-16918-1-git-send-email-clg@fr.ibm.com>
Sender: kvm-ppc-owner@vger.kernel.org
List-Id: kvm.vger.kernel.org

On Wed, Oct 29, 2014 at 09:38:41AM +0100, C=E9dric Le Goater wrote:
> This patchset adds a VHOST_VRING_F_BYTESWAP flag to inform the host=20
> to byteswap data of the vring when the guest and the host have a=20
> different endian order. The flag is stored at initialization in an=20
> attribute of the virtio queues. It is then used to byteswap, or not,=20
> the vring indexes and descriptors shared with the guest OS.
>=20
> The last patch adds the byteswapping of the virtio_net header as it=20
> is done in qemu.

Hi Cedric,

Thanks for submitting this.
One general problem with this approach, is that
it adds overhead e.g. for x86 on x86 unconditionally.

I will in a couple of days post a patch adding virtio 1.0
support for vhost.

This will serve as a better basis for cross-endian support in
vhost, on top.

I'll try to remember to Cc you.

> The patches apply on linux-3.18-rc2 and the tests were done on PowerP=
C=20
> using the following hosts :
> =20
>    	 fedora21/ppc64, utopic/ppc64le =20
>=20
> with various guests :=20
>=20
>    	 trusty/ppc64le, utopic/ppc64le, debian/ppc64le,=20
>    	 rhel6.5/ppc64, fedora21/ppc64, debian/ppc64
>=20
> Regressions tests for x86_64 were done a debian host using rhel6.6,=20
> fedora20 and debian guests.
> =09
>=20
> C=E9dric Le Goater (4):
>   vhost: add VHOST_VRING_F_BYTESWAP flag
>   vhost: add byteswap routines
>   vhost: byteswap virtqueue attributes
>   vhost_net: byteswap virtio_net header
>=20
>  drivers/vhost/net.c        |   39 +++++++++---
>  drivers/vhost/vhost.c      |  150 ++++++++++++++++++++++++++++++++++=
++++++----
>  drivers/vhost/vhost.h      |    1 +
>  include/uapi/linux/vhost.h |    3 +
>  4 files changed, 171 insertions(+), 22 deletions(-)
>=20
> --=20
> 1.7.10.4