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 ws5-mx01.kavi.com (ws5-mx01.kavi.com [34.193.7.191]) (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 ECD48EB64DD for ; Thu, 20 Jul 2023 21:14:21 +0000 (UTC) Received: from lists.oasis-open.org (oasis.ws5.connectedcommunity.org [10.110.1.242]) by ws5-mx01.kavi.com (Postfix) with ESMTP id 2EE95190908 for ; Thu, 20 Jul 2023 21:14:21 +0000 (UTC) Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id 0D66C98683E for ; Thu, 20 Jul 2023 21:14:21 +0000 (UTC) Received: from host09.ws5.connectedcommunity.org (host09.ws5.connectedcommunity.org [10.110.1.97]) by lists.oasis-open.org (Postfix) with QMQP id E4652983D01; Thu, 20 Jul 2023 21:14:20 +0000 (UTC) Mailing-List: contact virtio-dev-help@lists.oasis-open.org; run by ezmlm List-ID: Sender: Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id CD318986835 for ; Thu, 20 Jul 2023 21:14:20 +0000 (UTC) X-Virus-Scanned: amavisd-new at kavi.com X-MC-Unique: PrBgJYH3NH-8StBNapeqUg-1 X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1689887657; x=1690492457; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=un6P1F0G9Zbvn2sUzWbntYA2ZrQWiTinPEXM8NiA8hE=; b=EjdblMJFGMito9LLwiMbnpc4z77Bo1d5cBsz2KgNNOJi1GHsX0JyhCX2O64suJcMx6 9MXUF2IWmmYN32MYiYUgBV8qH7TJJmsB2hw01ETJRurnmeYiN1Ck5vE97CtDOKKlFQth w+NhDdeOvLHYkIM+RjUK1QnUTODeiZIYzVWdFH0a6bOQNBGO5zjPG+UxR74TmGnlQTOw zZz/DzrO1z4OizA9TsrIo3yWuRzYizHfJQBmJOkuX6CcpVCTo3HXCNlSEXzCNs4UbUVq K6HaGhGMB5jCLWLjg14GioR5kDXnqe8oQezXLgQfprCz3jAkngmNLmDg2RTc2KplqRiD UGPw== X-Gm-Message-State: ABy/qLbG6YrmmzK728yGuP/WOI83yZb6jq91RqRUfrJCfxFOg/gZzeIQ OXZLZIArRt93ZGWAfK1mfz8BxktG5XkrLJ2IuOS8uY6JzVTttI4/vjHPnvJqIgWZbV0/daTjV8O EVmKBIeJdGQS/nv/dj7QO+TEMh/MP X-Received: by 2002:a05:600c:2907:b0:3fc:1bd:95a6 with SMTP id i7-20020a05600c290700b003fc01bd95a6mr425wmd.31.1689887657456; Thu, 20 Jul 2023 14:14:17 -0700 (PDT) X-Google-Smtp-Source: APBJJlFxlCxXg4WKbNIgfHozaBrraPCVaOfXiMV8FVblJ5+C5h0e17/wboayhrcd+iIh1L9eZg4uxA== X-Received: by 2002:a05:600c:2907:b0:3fc:1bd:95a6 with SMTP id i7-20020a05600c290700b003fc01bd95a6mr416wmd.31.1689887657109; Thu, 20 Jul 2023 14:14:17 -0700 (PDT) Date: Thu, 20 Jul 2023 17:14:12 -0400 From: "Michael S. Tsirkin" To: Stefan Hajnoczi Cc: Alex =?iso-8859-1?Q?Benn=E9e?= , qemu-devel@nongnu.org, virtio-dev@lists.oasis-open.org, slp@redhat.com, marcandre.lureau@redhat.com, viresh.kumar@linaro.org, sgarzare@redhat.com, takahiro.akashi@linaro.org, erik.schilling@linaro.org, manos.pitsidianakis@linaro.org, mathieu.poirier@linaro.org Message-ID: <20230720171321-mutt-send-email-mst@kernel.org> References: <20230704123600.1808604-1-alex.bennee@linaro.org> <20230706124347-mutt-send-email-mst@kernel.org> <20230720195837.GJ210977@fedora> MIME-Version: 1.0 In-Reply-To: <20230720195837.GJ210977@fedora> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit Subject: [virtio-dev] Re: [RFC PATCH] docs/interop: define STANDALONE protocol feature for vhost-user On Thu, Jul 20, 2023 at 03:58:37PM -0400, Stefan Hajnoczi wrote: > On Thu, Jul 06, 2023 at 12:48:20PM -0400, Michael S. Tsirkin wrote: > > On Tue, Jul 04, 2023 at 01:36:00PM +0100, Alex Bennée wrote: > > > Currently QEMU has to know some details about the back-end to be able > > > to setup the guest. While various parts of the setup can be delegated > > > to the backend (for example config handling) this is a very piecemeal > > > approach. > > > > > This patch suggests a new feature flag (VHOST_USER_PROTOCOL_F_STANDALONE) > > > which the back-end can advertise which allows a probe message to be > > > sent to get all the details QEMU needs to know in one message. > > > > The reason we do piecemeal is that these existing pieces can be reused > > as others evolve or fall by wayside. > > > > For example, I can think of instances where you want to connect > > specifically to e.g. networking backend, and specify it > > on command line. Reasons could be many, e.g. for debugging, > > or to prevent connecting to wrong device on wrong channel > > (kind of like type safety). > > > > What is the reason to have 1 message? startup latency? > > How about we allow pipelining several messages then? > > Will be easier. > > This flag effectively says that the back-end is a full VIRTIO device > with a Device Status Register, Configuration Space, Virtqueues, the > device type, etc. This is different from previous vhost-user devices > which sometimes just offloaded certain virtqueues without providing the > full VIRTIO device (parts were emulated in the VMM). > > So for example, a vhost-user-net device does not support the controlq. > Alex's "standalone" device is a mode where the vhost-user protocol is > used but the back-end must implement a full virtio-net device. > Standalone devices are like vDPA device in this respect. > > I think it is important to have a protocol feature bit that advertises > that this is a standalone device, since the semantics are different for > traditional vhost-user-net devices. Not sure what that would gain as compared to a feature bit per message as we did previously. > However, I think having a single message is inflexible and duplicates > existing vhost-user protocol messages like VHOST_USER_GET_QUEUE_NUM. I > would prefer VHOST_USER_GET_DEVICE_ID and other messages. > > Stefan Exactly. -- MST --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org