From nobody Thu Nov 6 06:47:58 2025 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) client-ip=208.118.235.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; spf=pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=redhat.com Return-Path: Received: from lists.gnu.org (208.118.235.17 [208.118.235.17]) by mx.zohomail.com with SMTPS id 1537443925766211.54174743768783; Thu, 20 Sep 2018 04:45:25 -0700 (PDT) Received: from localhost ([::1]:49815 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1g2xOU-0007qt-64 for importer@patchew.org; Thu, 20 Sep 2018 07:45:14 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60172) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1g2xNX-0007XS-TV for qemu-devel@nongnu.org; Thu, 20 Sep 2018 07:44:16 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1g2xNT-00006Z-Pf for qemu-devel@nongnu.org; Thu, 20 Sep 2018 07:44:15 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48614) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1g2xNT-00005k-FB for qemu-devel@nongnu.org; Thu, 20 Sep 2018 07:44:11 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 8AD0630024D8 for ; Thu, 20 Sep 2018 11:44:10 +0000 (UTC) Received: from paraplu.localdomain (ovpn-117-100.ams2.redhat.com [10.36.117.100]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5BD107FCAD; Thu, 20 Sep 2018 11:44:09 +0000 (UTC) From: Kashyap Chamarthy To: qemu-devel@nongnu.org Date: Thu, 20 Sep 2018 13:44:06 +0200 Message-Id: <20180920114406.20818-1-kchamart@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.43]); Thu, 20 Sep 2018 11:44:10 +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: [Qemu-devel] [PATCH] Deprecate QMP `cpu-add` X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kashyap Chamarthy , armbru@redhat.com, ehabkost@redhat.com Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail: RDMRC_1 RSF_0 Z_629925259 SPT_0 Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" The intended functionality of QMP command `cpu-add` is replaced by `device_add` (and `query-hotpluggable-cpus`). So let's deprecate `cpu-add`. A complete example of vCPU hotplug with the recommended way, using `device_add`: (1) Launch QEMU as follows (note that the "maxcpus" is mandatory to allow vCPU hotplug): $ qemu-system-x86_64 -display none -no-user-config -m 2048 \ -nodefaults -monitor stdio -machine pc,accel=3Dkvm,usb=3Doff \ -smp 1,maxcpus=3D2 -cpu IvyBridge-IBRS \ -blockdev node-name=3Dnode-Base,driver=3Dqcow2,file.driver=3Dfile,f= ile.filename=3D./base.qcow2 \ -device virtio-blk,drive=3Dnode-Base,id=3Dvirtio0 -qmp unix:/tmp/qm= p-sock,server,nowait (2) Run 'qmp-shell' (located in the source tree) to connect to the just-launched QEMU: $> ./qmp/qmp-shell -p -v /tmp/qmp-sock [...] (QEMU) (3) Check which socket is free to allow hotplugging a CPU: (QEMU) query-hotpluggable-cpus { "execute":"query-hotpluggable-cpus", "arguments":{ } } { "return":[ { "type":"IvyBridge-IBRS-x86_64-cpu", "vcpus-count":1, "props":{ "socket-id":1, "core-id":0, "thread-id":0 } }, { "qom-path":"/machine/unattached/device[0]", "type":"IvyBridge-IBRS-x86_64-cpu", "vcpus-count":1, "props":{ "socket-id":0, "core-id":0, "thread-id":0 } } ] } (QEMU) (4) We can see that socket 1 is free, so use `device_add` to hotplug "IvyBridge-IBRS-x86_64-cpu": (QEMU) device_add id=3Dcpu-2 driver=3DIvyBridge-IBRS-x86_64-cpu socket-= id=3D1 core-id=3D0 thread-id=3D0 { "execute": "device_add", "arguments": { "socket-id": 1, "driver": "IvyBridge-IBRS-x86_64-cpu", "id": "cpu-2", "core-id": 0, "thread-id": 0 } } { "return": {} } (QEMU) (5) Optionally, run QMP `query-cpus-fast` for some details about the vCPUs. Suggested-by: Eduardo Habkost --- Also shouldn't we update tests/cpu-plug-test.c to make it use `device_add`. Can take a stab at it, if you'd like me to. --- qapi/misc.json | 6 +++++- qemu-deprecated.texi | 5 +++++ 2 files changed, 10 insertions(+), 1 deletion(-) diff --git a/qapi/misc.json b/qapi/misc.json index d450cfef21..83bc9ad0ee 100644 --- a/qapi/misc.json +++ b/qapi/misc.json @@ -1104,7 +1104,11 @@ ## # @cpu-add: # -# Adds CPU with specified ID +# Adds CPU with specified ID. +# +# Notes: This command is deprecated. The `device_add` command should be +# used instead. See the `query-hotpluggable-cpus` command for +# details. # # @id: ID of CPU to be created, valid values [0..max_cpus) # diff --git a/qemu-deprecated.texi b/qemu-deprecated.texi index 1b9c007f12..9c6d70d43a 100644 --- a/qemu-deprecated.texi +++ b/qemu-deprecated.texi @@ -155,6 +155,11 @@ The ``query-cpus'' command is replaced by the ``query-= cpus-fast'' command. The ``arch'' output member of the ``query-cpus-fast'' command is replaced by the ``target'' output member. =20 +@subsection cpu-add (since 3.1) + +The intended functionality of ``cpu-add'' command, which is the ability +to hot-plug vCPUs, can now be achieved by the ``device_add'' command. + @section System emulator devices =20 @subsection ivshmem (since 2.6.0) --=20 2.17.1