From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59953) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aY9TN-0004bR-Ua for qemu-devel@nongnu.org; Tue, 23 Feb 2016 04:41:39 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aY9TK-0006US-Kl for qemu-devel@nongnu.org; Tue, 23 Feb 2016 04:41:37 -0500 Received: from e23smtp05.au.ibm.com ([202.81.31.147]:55921) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aY9TK-0006Tn-3D for qemu-devel@nongnu.org; Tue, 23 Feb 2016 04:41:34 -0500 Received: from localhost by e23smtp05.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 23 Feb 2016 19:41:30 +1000 Date: Tue, 23 Feb 2016 15:10:26 +0530 From: Bharata B Rao Message-ID: <20160223094026.GA21081@in.ibm.com> References: <20160223052431.GS2808@voom.fritz.box> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160223052431.GS2808@voom.fritz.box> Subject: Re: [Qemu-devel] CPU hotplug, again Reply-To: bharata@linux.vnet.ibm.com List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: David Gibson Cc: thuth@redhat.com, ehabkost@redhat.com, armbru@redhat.com, agraf@suse.de, qemu-devel@nongnu.org, qemu-ppc@nongnu.org, pbonzini@redhat.com, imammedo@redhat.com, Andreas =?iso-8859-1?Q?F=E4rber?= On Tue, Feb 23, 2016 at 04:24:31PM +1100, David Gibson wrote: > Hi Andreas, > > I've now found (with Thomas' help) your RFC series for socket/core > based cpu hotplug on x86 > (https://github.com/afaerber/qemu-cpu/compare/qom-cpu-x86). It seems > sensible enough as far as it goes, but doesn't seem to address a bunch > of the things that I was attempting to do with the cpu-package > proposal - and which we absolutely need for cpu hotplug on Power. > > 1) What interface do you envisage beyond cpu_add? > > The patches I see just construct extra socket and core objects, but > still control hotplug (for x86) through the cpu_add interface. That > interface is absolutely unusable on Power, since it operates on a > per-thread basis, whereas the PAPR guest<->host interfaces can only > communicate information at a per-core granularity. > > 2) When hotplugging at core or socket granularity, where would the > code to construct the individual thread objects sit? > > Your series has the construction done in both the machine init path > and the hotplug path. The latter works because hotplug occurs at > thread granularity. If we're hotplugging at core or socket > granularity what would do the construct? The core/socket object > itself (in instance_init? in realize?); the hotplug handler? > something else? > > 3) How does the management layer determine what is pluggable? > > Both the number of pluggable slots, and what it will need to do to > populate them. > > 4) How do we enforce that toplogies illegal for the platform can't be > constructed? 5) QOM-links Andreas, You have often talked about setting up links from machine object to the CPU objects. Would the below code correctly capture that idea of yours ? #define SPAPR_MACHINE_CPU_CORE_PROP "core" /* MachineClass.init for sPAPR */ static void ppc_spapr_init(MachineState *machine) { sPAPRMachineState *spapr = SPAPR_MACHINE(machine); int spapr_smp_cores = smp_cpus / smp_threads; int spapr_max_cores = max_cpus / smp_threads; ... for (i = 0; i < spapr_max_cores; i++) { Object *obj = object_new(TYPE_SPAPR_CPU_CORE); sPAPRCPUCore *core = SPAPR_CPU_CORE(obj); char name[32]; snprintf(name, sizeof(name), "%s[%d]", SPAPR_MACHINE_CPU_CORE_PROP, i); /* * Create links from machine objects to all possible cores. */ object_property_add_link(OBJECT(spapr), name, TYPE_SPAPR_CPU_CORE, (Object **)&spapr->core[i], NULL, NULL, &error_abort); /* * Set the QOM link from machine object to core object for all * boot time CPUs specified with -smp. For rest of the hotpluggable * cores this is done from the core hotplug path. */ if (i < spapr_smp_cores) { object_property_set_link(OBJECT(spapr), OBJECT(core), SPAPR_MACHINE_CPU_CORE_PROP, &error_abort); } ... }