From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Thu, 5 Oct 2023 13:43:33 -0400 From: Stefan Hajnoczi Message-ID: <20231005174333.GD1342722@fedora> References: <20231004125904.110781-1-hreitz@redhat.com> <20231004125904.110781-4-hreitz@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="t+JYja1hNqvjfZWk" Content-Disposition: inline In-Reply-To: <20231004125904.110781-4-hreitz@redhat.com> Subject: Re: [Virtio-fs] [PATCH v4 3/8] vhost-user.rst: Clarify enabling/disabling vrings List-Id: Development discussions about virtio-fs List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Hanna Czenczek Cc: qemu-devel@nongnu.org, virtio-fs@redhat.com, "Michael S . Tsirkin" , German Maglione , Eugenio =?iso-8859-1?Q?P=E9rez?= , Anton Kuchin --t+JYja1hNqvjfZWk Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Oct 04, 2023 at 02:58:59PM +0200, Hanna Czenczek wrote: > Currently, the vhost-user documentation says that rings are to be > initialized in a disabled state when VHOST_USER_F_PROTOCOL_FEATURES is > negotiated. However, by the time of feature negotiation, all rings have > already been initialized, so it is not entirely clear what this means. >=20 > At least the vhost-user-backend Rust crate's implementation interpreted > it to mean that whenever this feature is negotiated, all rings are to > put into a disabled state, which means that every SET_FEATURES call > would disable all rings, effectively halting the device. This is > problematic because the VHOST_F_LOG_ALL feature is also set or cleared > this way, which happens during migration. Doing so should not halt the > device. >=20 > Other implementations have interpreted this to mean that the device is > to be initialized with all rings disabled, and a subsequent SET_FEATURES > call that does not set VHOST_USER_F_PROTOCOL_FEATURES will enable all of > them. Here, SET_FEATURES will never disable any ring. >=20 > This interpretation does not suffer the problem of unintentionally > halting the device whenever features are set or cleared, so it seems > better and more reasonable. >=20 > We can clarify this in the documentation by making it explicit that the > enabled/disabled state is tracked even while the vring is stopped. > Every vring is initialized in a disabled state, and SET_FEATURES without > VHOST_USER_F_PROTOCOL_FEATURES simply becomes one way to enable all > vrings. >=20 > Signed-off-by: Hanna Czenczek > --- > docs/interop/vhost-user.rst | 32 +++++++++++++++++--------------- > 1 file changed, 17 insertions(+), 15 deletions(-) Reviewed-by: Stefan Hajnoczi --t+JYja1hNqvjfZWk Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmUe9cUACgkQnKSrs4Gr c8hqeQf+J8jHFezwIR2ygsUKJwEjYNdeoaFotnS5EMqR8I+Hw2lPWz6qeWKBKCxt 97zucS5Cuae/QH8sMKlb+c9FvGAG+3ibNFTQNo0U51s7eZzUQVLTjRYFLY+q7e1Q fcXqP0ju7ZoXvEYsjuaLqXMyfPNWLMesoOpE9nmPErW7QtZXMd5utSFphqUNIp3O GQGKynO33pfkolMqLBBa9tcYV6bSfKV/jlJMmMz2AZIYvmfj1uajomU08JLuVznt Lpx/fZj8QLkyKeTK63Xr0YcyV/XnSRlW/UuJIluis0Uagc42G03wNVmD32TAL5NE 30sSwJAK+GI5q+Ae8UI4msWvN0BuMQ== =8Kbw -----END PGP SIGNATURE----- --t+JYja1hNqvjfZWk-- 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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id EB4BAE9271B for ; Thu, 5 Oct 2023 17:44:28 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qoSO1-0004fM-QZ; Thu, 05 Oct 2023 13:43:45 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qoSO0-0004eU-1h for qemu-devel@nongnu.org; Thu, 05 Oct 2023 13:43:44 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qoSNx-0004om-HS for qemu-devel@nongnu.org; Thu, 05 Oct 2023 13:43:43 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1696527819; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=p0itKNhzeMx74t/+gK5QA1MDIfNAGDMVUcXIcUF6HFo=; b=VTXDN19ALSuw0SGKuTGLokAbjtTMCka1ZCOJVeF9FUCtzzYDxXRtjuHy50gOQT2MWlu4an 4fs3/1N74dj119yy4KC8xes8rX+QCkSbDuQIO8zMRgB+X+RuuUMYV9ytDzQXRJipm2tn38 dx1/ArICQgdpWEJej8Mo228GJn1iN+g= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-490-1mAhzpflNwmb9QLrWpXk3w-1; Thu, 05 Oct 2023 13:43:35 -0400 X-MC-Unique: 1mAhzpflNwmb9QLrWpXk3w-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 6F5733C1ACD6; Thu, 5 Oct 2023 17:43:35 +0000 (UTC) Received: from localhost (unknown [10.39.192.20]) by smtp.corp.redhat.com (Postfix) with ESMTP id E75C940B3ECE; Thu, 5 Oct 2023 17:43:34 +0000 (UTC) Date: Thu, 5 Oct 2023 13:43:33 -0400 From: Stefan Hajnoczi To: Hanna Czenczek Cc: qemu-devel@nongnu.org, virtio-fs@redhat.com, "Michael S . Tsirkin" , German Maglione , Eugenio =?iso-8859-1?Q?P=E9rez?= , Anton Kuchin Subject: Re: [PATCH v4 3/8] vhost-user.rst: Clarify enabling/disabling vrings Message-ID: <20231005174333.GD1342722@fedora> References: <20231004125904.110781-1-hreitz@redhat.com> <20231004125904.110781-4-hreitz@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="t+JYja1hNqvjfZWk" Content-Disposition: inline In-Reply-To: <20231004125904.110781-4-hreitz@redhat.com> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.1 Received-SPF: pass client-ip=170.10.133.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org --t+JYja1hNqvjfZWk Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Oct 04, 2023 at 02:58:59PM +0200, Hanna Czenczek wrote: > Currently, the vhost-user documentation says that rings are to be > initialized in a disabled state when VHOST_USER_F_PROTOCOL_FEATURES is > negotiated. However, by the time of feature negotiation, all rings have > already been initialized, so it is not entirely clear what this means. >=20 > At least the vhost-user-backend Rust crate's implementation interpreted > it to mean that whenever this feature is negotiated, all rings are to > put into a disabled state, which means that every SET_FEATURES call > would disable all rings, effectively halting the device. This is > problematic because the VHOST_F_LOG_ALL feature is also set or cleared > this way, which happens during migration. Doing so should not halt the > device. >=20 > Other implementations have interpreted this to mean that the device is > to be initialized with all rings disabled, and a subsequent SET_FEATURES > call that does not set VHOST_USER_F_PROTOCOL_FEATURES will enable all of > them. Here, SET_FEATURES will never disable any ring. >=20 > This interpretation does not suffer the problem of unintentionally > halting the device whenever features are set or cleared, so it seems > better and more reasonable. >=20 > We can clarify this in the documentation by making it explicit that the > enabled/disabled state is tracked even while the vring is stopped. > Every vring is initialized in a disabled state, and SET_FEATURES without > VHOST_USER_F_PROTOCOL_FEATURES simply becomes one way to enable all > vrings. >=20 > Signed-off-by: Hanna Czenczek > --- > docs/interop/vhost-user.rst | 32 +++++++++++++++++--------------- > 1 file changed, 17 insertions(+), 15 deletions(-) Reviewed-by: Stefan Hajnoczi --t+JYja1hNqvjfZWk Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmUe9cUACgkQnKSrs4Gr c8hqeQf+J8jHFezwIR2ygsUKJwEjYNdeoaFotnS5EMqR8I+Hw2lPWz6qeWKBKCxt 97zucS5Cuae/QH8sMKlb+c9FvGAG+3ibNFTQNo0U51s7eZzUQVLTjRYFLY+q7e1Q fcXqP0ju7ZoXvEYsjuaLqXMyfPNWLMesoOpE9nmPErW7QtZXMd5utSFphqUNIp3O GQGKynO33pfkolMqLBBa9tcYV6bSfKV/jlJMmMz2AZIYvmfj1uajomU08JLuVznt Lpx/fZj8QLkyKeTK63Xr0YcyV/XnSRlW/UuJIluis0Uagc42G03wNVmD32TAL5NE 30sSwJAK+GI5q+Ae8UI4msWvN0BuMQ== =8Kbw -----END PGP SIGNATURE----- --t+JYja1hNqvjfZWk--