From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56029) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eGwEo-0000vf-5t for qemu-devel@nongnu.org; Mon, 20 Nov 2017 19:16:31 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eGwEj-0000P7-Tq for qemu-devel@nongnu.org; Mon, 20 Nov 2017 19:16:29 -0500 Received: from mx1.redhat.com ([209.132.183.28]:56230) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eGwEj-0000Ou-NK for qemu-devel@nongnu.org; Mon, 20 Nov 2017 19:16:25 -0500 References: <1510865080-32027-1-git-send-email-changpeng.liu@intel.com> <1510865080-32027-2-git-send-email-changpeng.liu@intel.com> <20171120162631.GK4516@stefanha-x1.localdomain> <20171120224001-mutt-send-email-mst@kernel.org> From: Paolo Bonzini Message-ID: <776f5005-8bb8-773a-1f16-56b5675e7d74@redhat.com> Date: Tue, 21 Nov 2017 01:16:12 +0100 MIME-Version: 1.0 In-Reply-To: <20171120224001-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v5 1/4] vhost-user: add new vhost user messages to support virtio config space List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" , Stefan Hajnoczi Cc: Changpeng Liu , qemu-devel@nongnu.org, marcandre.lureau@redhat.com, felipe@nutanix.com, james.r.harris@intel.com On 20/11/2017 21:44, Michael S. Tsirkin wrote: > Live migrations is supposed to be migrating guest writeable state too. > If you mean migrating RO fields like size, then > I don't think it's a good idea to reuse SET_CONFIG for that. > SET_CONFIG should obey exactly the virtio semantics. > > And I agree, it should say that slave must treat it as a write, > and get config as a read according to virtio semantics. > > If someone needs to pass configuration from qemu to > slave, let's add specific messages with precisely defined semantics. Fair enough, but I'd add nevertheless a 32-bit flags field to both GET_CONFIG and SET_CONFIG, and document that the slave MUST check that it is zero and otherwise fail. Paolo