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Violators will be prosecuted for from ; Thu, 26 Jan 2017 19:56:41 +0530 Date: Thu, 26 Jan 2017 19:56:35 +0530 From: Bharata B Rao Reply-To: bharata@linux.vnet.ibm.com References: <1466145399-32209-1-git-send-email-david@gibson.dropbear.id.au> <1466145399-32209-16-git-send-email-david@gibson.dropbear.id.au> <20170126123258.2d34fe95@Igors-MacBook-Pro.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170126123258.2d34fe95@Igors-MacBook-Pro.local> Message-Id: <20170126142635.GA8653@in.ibm.com> Subject: Re: [Qemu-devel] [PULL 15/18] spapr: CPU hot unplug support List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Igor Mammedov Cc: David Gibson , peter.maydell@linaro.org, agraf@suse.de, aik@ozlabs.ru, mdroth@linux.vnet.ibm.com, qemu-ppc@nongnu.org, qemu-devel@nongnu.org On Thu, Jan 26, 2017 at 12:32:58PM +0100, Igor Mammedov wrote: > On Fri, 17 Jun 2016 16:36:36 +1000 > David Gibson wrote: > > > From: Bharata B Rao > > > > Remove the CPU core device by removing the underlying CPU thread devices. > > Hot removal of CPU for sPAPR guests is achieved by sending the hot unplug > > notification to the guest. Release the vCPU object after CPU hot unplug so > > that vCPU fd can be parked and reused. > > > > Signed-off-by: Bharata B Rao > > Signed-off-by: David Gibson > [...] > > > Bharata, > > Here is some notes I've made while auditing spapr cpu hotplug code. > > spapr_core_release() should be spapr_core_unrealize() > except of machine related > spapr->cores[cc->core_id / smt] = NULL; > which should go to spapr_core_unplug() There were some issues in calling cpu_remove_[sync] from unrealize path. I know that x86 does that way. let me remember and get back on this. > > > +static void spapr_core_release(DeviceState *dev, void *opaque) > > +{ > > + sPAPRCPUCore *sc = SPAPR_CPU_CORE(OBJECT(dev)); > > + const char *typename = object_class_get_name(sc->cpu_class); > > + size_t size = object_type_get_instance_size(typename); > > + sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine()); > > + sPAPRCPUCore *core = SPAPR_CPU_CORE(OBJECT(dev)); > > + CPUCore *cc = CPU_CORE(dev); > > + int smt = kvmppc_smt_threads(); > > + int i; > > + > > + for (i = 0; i < cc->nr_threads; i++) { > > + void *obj = sc->threads + i * size; > > + DeviceState *dev = DEVICE(obj); > > + CPUState *cs = CPU(dev); > > + PowerPCCPU *cpu = POWERPC_CPU(cs); > > + > > + spapr_cpu_destroy(cpu); > > + cpu_remove_sync(cs); > > + object_unparent(obj); > > + } > > + > > + spapr->cores[cc->core_id / smt] = NULL; > > + > > + g_free(core->threads); > > + object_unparent(OBJECT(dev)); > > +} > > + > > spapr_core_[un]plug() functions belong to machine code and should > be in hw/ppc/spapr.c That's how the series started, but eventually we consolidated all core related routines in spapr_cpu_core.c > > > +void spapr_core_unplug(HotplugHandler *hotplug_dev, DeviceState *dev, > > + Error **errp) > > +{ > > + sPAPRCPUCore *core = SPAPR_CPU_CORE(OBJECT(dev)); > > + PowerPCCPU *cpu = POWERPC_CPU(core->threads); > > + int id = ppc_get_vcpu_dt_id(cpu); > > + sPAPRDRConnector *drc = > > + spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_CPU, id); > > + sPAPRDRConnectorClass *drck; > > + Error *local_err = NULL; > > + > > + g_assert(drc); > > + > > + drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc); > > + drck->detach(drc, dev, spapr_core_release, NULL, &local_err); > > Could you explain call flow during cpu unplug? In response to unplug request, spapr_core_unplug() gets called which does a detach() on the associated DRC object. The detach() registers a callback (spapr_core_release) and signals the guest about the unplug request. When the guest is ready to let go of the CPU core, DRC subsystem ends up calling the callback spapr_core_release. For each of the CPU thread objects of the core, spapr_core_release will call cpu_remove_sync() and waits for the CPU to be really removed. cpu_remove will result in CPU unrealize function being called (ppc_cpu_unrealizefn) for each of the removed CPU. After we are done waiting for all the threads' removal, the core object is ready for removal. > > My expectations were that unplug_request() handler asks for CPU removal > and unplug() handler removes CPU. > It's obviously messed up somehow. When we did CPU unplug, we didn't really implement ->unplug_request() for sPAPR. It was added later when memory unplug came in. Regards, Bharata.