pc: make sure that guest isn't able to unplug the first cpu
The first cpu unplug wasn't ever supported and corresponding monitor/qmp commands refuse to unplug it. However guest is able to issue eject request either using following command: # echo 1 >/sys/devices/system/cpu/cpu0/firmware_node/eject or directly writing to cpu hotplug registers, which makes qemu crash with SIGSEGV following back trace: kvm_flush_coalesced_mmio_buffer () while (ring->first != ring->last) ... qemu_flush_coalesced_mmio_buffer prepare_mmio_access flatview_read_continue flatview_read address_space_read_full address_space_rw kvm_cpu_exec(cpu!0) qemu_kvm_cpu_thread_fn the reason for which is that ring == KVMState::coalesced_mmio_ring happens to be a part of 1st CPU that was uplugged by guest. Fix it by forbidding 1st cpu unplug from guest side and in addition remove CPU0._EJ0 ACPI method to make clear that unplug of the first CPU is not supported. Signed-off-by: Igor Mammedov <imammedo@redhat.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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@ -117,7 +117,7 @@ static void cpu_hotplug_wr(void *opaque, hwaddr addr, uint64_t data,
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DeviceState *dev = NULL;
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DeviceState *dev = NULL;
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HotplugHandler *hotplug_ctrl = NULL;
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HotplugHandler *hotplug_ctrl = NULL;
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if (!cdev->cpu) {
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if (!cdev->cpu || cdev->cpu == first_cpu) {
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trace_cpuhp_acpi_ejecting_invalid_cpu(cpu_st->selector);
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trace_cpuhp_acpi_ejecting_invalid_cpu(cpu_st->selector);
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break;
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break;
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}
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}
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@ -541,9 +541,11 @@ void build_cpus_aml(Aml *table, MachineState *machine, CPUHotplugFeatures opts,
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aml_buffer(madt_buf->len, (uint8_t *)madt_buf->data)));
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aml_buffer(madt_buf->len, (uint8_t *)madt_buf->data)));
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g_array_free(madt_buf, true);
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g_array_free(madt_buf, true);
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method = aml_method("_EJ0", 1, AML_NOTSERIALIZED);
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if (CPU(arch_ids->cpus[i].cpu) != first_cpu) {
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aml_append(method, aml_call1(CPU_EJECT_METHOD, uid));
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method = aml_method("_EJ0", 1, AML_NOTSERIALIZED);
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aml_append(dev, method);
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aml_append(method, aml_call1(CPU_EJECT_METHOD, uid));
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aml_append(dev, method);
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}
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method = aml_method("_OST", 3, AML_SERIALIZED);
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method = aml_method("_OST", 3, AML_SERIALIZED);
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aml_append(method,
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aml_append(method,
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