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Tue, 7 Jul 2020 21:49:17 +0000 (UTC) Date: Tue, 7 Jul 2020 17:49:17 -0400 From: Eduardo Habkost To: Thiago Jung Bauermann Subject: Re: [PATCH] cpu: Add starts_halted() method Message-ID: <20200707214917.GX7276@habkost.net> References: <20200707204333.261506-1-bauerman@linux.ibm.com> MIME-Version: 1.0 In-Reply-To: <20200707204333.261506-1-bauerman@linux.ibm.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=ehabkost@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=207.211.31.81; envelope-from=ehabkost@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/07 17:25:09 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-ppc@nongnu.org, qemu-devel@nongnu.org, David Gibson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, Jul 07, 2020 at 05:43:33PM -0300, Thiago Jung Bauermann wrote: > PowerPC sPAPRs CPUs start in the halted state, but generic QEMU code > assumes that CPUs start in the non-halted state. spapr_reset_vcpu() > attempts to rectify this by setting CPUState::halted to 1. But that's too > late for hotplugged CPUs in a machine configured with 2 or mor threads per > core. > > By then, other parts of QEMU have already caused the vCPU to run in an > unitialized state a couple of times. For example, ppc_cpu_reset() calls > ppc_tlb_invalidate_all(), which ends up calling async_run_on_cpu(). This > kicks the new vCPU while it has CPUState::halted = 0, causing QEMU to issue > a KVM_RUN ioctl on the new vCPU before the guest is able to make the > start-cpu RTAS call to initialize its register state. > > This doesn't seem to cause visible issues for regular guests, but on a > secure guest running under the Ultravisor it does. The Ultravisor relies on > being able to snoop on the start-cpu RTAS call to map vCPUs to guests, and > this issue causes it to see a stray vCPU that doesn't belong to any guest. > > Fix by adding a starts_halted() method to the CPUState class, and making it > return 1 if the machine is an sPAPR guest. > > Signed-off-by: Thiago Jung Bauermann [...] > +static uint32_t ppc_cpu_starts_halted(void) > +{ > + SpaprMachineState *spapr = > + (SpaprMachineState *) object_dynamic_cast(qdev_get_machine(), > + TYPE_SPAPR_MACHINE); Wouldn't it be simpler to just implement this as a MachineClass boolean field? e.g.: Signed-off-by: Eduardo Habkost --- diff --git a/include/hw/boards.h b/include/hw/boards.h index 426ce5f625..ffadc7a17d 100644 --- a/include/hw/boards.h +++ b/include/hw/boards.h @@ -215,6 +215,7 @@ struct MachineClass { bool nvdimm_supported; bool numa_mem_supported; bool auto_enable_numa; + bool cpu_starts_halted; const char *default_ram_id; HotplugHandler *(*get_hotplug_handler)(MachineState *machine, diff --git a/hw/core/cpu.c b/hw/core/cpu.c index 0f23409f1d..08dd504034 100644 --- a/hw/core/cpu.c +++ b/hw/core/cpu.c @@ -252,6 +252,7 @@ static void cpu_common_reset(DeviceState *dev) { CPUState *cpu = CPU(dev); CPUClass *cc = CPU_GET_CLASS(cpu); + MachineState *machine = object_dynamic_cast(qdev_get_machine(), TYPE_MACHINE); if (qemu_loglevel_mask(CPU_LOG_RESET)) { qemu_log("CPU Reset (CPU %d)\n", cpu->cpu_index); @@ -259,7 +260,7 @@ static void cpu_common_reset(DeviceState *dev) } cpu->interrupt_request = 0; - cpu->halted = 0; + cpu->halted = machine ? MACHINE_GET_CLASS(machine)->cpu_starts_halted : 0; cpu->mem_io_pc = 0; cpu->icount_extra = 0; atomic_set(&cpu->icount_decr_ptr->u32, 0); diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c index f6f034d039..d16ec33033 100644 --- a/hw/ppc/spapr.c +++ b/hw/ppc/spapr.c @@ -4487,6 +4487,7 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data) mc->default_cpu_type = POWERPC_CPU_TYPE_NAME("power9_v2.0"); mc->has_hotpluggable_cpus = true; mc->nvdimm_supported = true; + mc->cpu_starts_halted = true; smc->resize_hpt_default = SPAPR_RESIZE_HPT_ENABLED; fwc->get_dev_path = spapr_get_fw_dev_path; nc->nmi_monitor_handler = spapr_nmi; > + > + /* > + * In sPAPR, all CPUs start halted. CPU0 is unhalted from the machine level > + * reset code and the rest are explicitly started up by the guest using an > + * RTAS call. > + */ > + return spapr != NULL; > +} > + -- Eduardo