From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 87BB8C76192 for ; Wed, 17 Jul 2019 10:15:16 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 606A821743 for ; Wed, 17 Jul 2019 10:15:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 606A821743 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:55612 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hngxu-0006TO-Fp for qemu-devel@archiver.kernel.org; Wed, 17 Jul 2019 06:15:14 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:49963) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hngxi-0005t3-9b for qemu-devel@nongnu.org; Wed, 17 Jul 2019 06:15:03 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hngxh-0005Em-7S for qemu-devel@nongnu.org; Wed, 17 Jul 2019 06:15:02 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40354) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hngxg-0005Co-VP for qemu-devel@nongnu.org; Wed, 17 Jul 2019 06:15:01 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id DED1F3093385; Wed, 17 Jul 2019 10:14:59 +0000 (UTC) Received: from localhost (ovpn-117-7.ams2.redhat.com [10.36.117.7]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9BA135D71D; Wed, 17 Jul 2019 10:14:54 +0000 (UTC) Date: Wed, 17 Jul 2019 11:14:53 +0100 From: Stefan Hajnoczi To: qemu-devel@nongnu.org Message-ID: <20190717101453.GE7341@stefanha-x1.localdomain> References: <20190624091304.666-1-stefanha@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="2hMgfIw2X+zgXrFs" Content-Disposition: inline In-Reply-To: <20190624091304.666-1-stefanha@redhat.com> User-Agent: Mutt/1.12.0 (2019-05-25) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.45]); Wed, 17 Jul 2019 10:14:59 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH] docs: clarify multiqueue vs multiple virtqueues X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: =?iso-8859-1?Q?Marc-Andr=E9?= Lureau , Sebastien Boeuf , Cathy Zhang , "Michael S. Tsirkin" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" --2hMgfIw2X+zgXrFs Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Jun 24, 2019 at 10:13:04AM +0100, Stefan Hajnoczi wrote: > The vhost-user specification does not explain when > VHOST_USER_PROTOCOL_F_MQ must be implemented. This may lead > implementors of vhost-user masters to believe that this protocol feature > is required for any device that has multiple virtqueues. That would be > a mistake since existing vhost-user slaves offer multiple virtqueues but > do not advertise VHOST_USER_PROTOCOL_F_MQ. >=20 > For example, a vhost-net device with one rx/tx queue pair is not > multiqueue. The slave does not need to advertise > VHOST_USER_PROTOCOL_F_MQ. Therefore the master must assume it has these > virtqueues and cannot rely on askingt the slave how many virtqueues > exist. >=20 > Extend the specification to explain the different between true > multiqueue and regular devices with a fixed virtqueue layout. >=20 > Signed-off-by: Stefan Hajnoczi > --- > Based-on: <20190621094005.4134-1-stefanha@redhat.com> > --- > docs/interop/vhost-user.rst | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) Ping? >=20 > diff --git a/docs/interop/vhost-user.rst b/docs/interop/vhost-user.rst > index 5750668aba..7827b710aa 100644 > --- a/docs/interop/vhost-user.rst > +++ b/docs/interop/vhost-user.rst > @@ -324,6 +324,15 @@ must support changing some configuration aspects on = the fly. > Multiple queue support > ---------------------- > =20 > +Many devices have a fixed number of virtqueues. In this case the master > +already knows the number of available virtqueues without communicating w= ith the > +slave. > + > +Some devices do not have a fixed number of virtqueues. Instead the maxi= mum > +number of virtqueues is chosen by the slave. The number can depend on h= ost > +resource availability or slave implementation details. Such devices are= called > +multiple queue devices. > + > Multiple queue support allows the slave to advertise the maximum number = of > queues. This is treated as a protocol extension, hence the slave has to > implement protocol features first. The multiple queues feature is suppor= ted > @@ -339,6 +348,14 @@ queue in the sent message to identify a specified qu= eue. > The master enables queues by sending message ``VHOST_USER_SET_VRING_ENAB= LE``. > vhost-user-net has historically automatically enabled the first queue pa= ir. > =20 > +Slaves should always implement the ``VHOST_USER_PROTOCOL_F_MQ`` protocol > +feature, even for devices with a fixed number of virtqueues, since it is= simple > +to implement and offers a degree of introspection. > + > +Masters must not rely on the ``VHOST_USER_PROTOCOL_F_MQ`` protocol featu= re for > +devices with a fixed number of virtqueues. Only true multiqueue devices > +require this protocol feature. > + > Migration > --------- > =20 > --=20 > 2.21.0 >=20 --2hMgfIw2X+zgXrFs Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAl0u9R0ACgkQnKSrs4Gr c8hhTgf/cxAraawJ9czUhD+pNdIyemF2qJ5YGKEBwq9XcA6lyyN2tixv0FMF9bFq UWTRNZHUZuu2qbE2U43JG0pumQdLDYSZ03SSyWx4vXLSy1zRHC5tSX73njsjPG18 OlppSoUT+TfPPnG5Gvj6t3Egt0UL8Oowbop8XADNtUUjAo7VMpw3fWl1MmJv0Tbp 71LvYw4FGl8dDZ6xLb7WBRAs7pDneRYj2UfTUYVDP0fVJjCfsMNvCoLaGR81NB1f 1gRKC8VuFyXS4ExYmXE3EXKlYd7CB9DRnPnjUCxPVICukQZ4TAq8JcQzJADCxSVJ qR3DlmDWhONIOYndjvDuLRoTdrksrQ== =w2ar -----END PGP SIGNATURE----- --2hMgfIw2X+zgXrFs--