xref: /openbmc/qemu/hw/ppc/spapr_vio.c (revision fe7f9b8e)
1 /*
2  * QEMU sPAPR VIO code
3  *
4  * Copyright (c) 2010 David Gibson, IBM Corporation <dwg@au1.ibm.com>
5  * Based on the s390 virtio bus code:
6  * Copyright (c) 2009 Alexander Graf <agraf@suse.de>
7  *
8  * This library is free software; you can redistribute it and/or
9  * modify it under the terms of the GNU Lesser General Public
10  * License as published by the Free Software Foundation; either
11  * version 2 of the License, or (at your option) any later version.
12  *
13  * This library is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
16  * Lesser General Public License for more details.
17  *
18  * You should have received a copy of the GNU Lesser General Public
19  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
20  */
21 
22 #include "qemu/osdep.h"
23 #include "qemu/error-report.h"
24 #include "qapi/error.h"
25 #include "hw/hw.h"
26 #include "qemu/log.h"
27 #include "sysemu/sysemu.h"
28 #include "hw/boards.h"
29 #include "hw/loader.h"
30 #include "elf.h"
31 #include "hw/sysbus.h"
32 #include "sysemu/kvm.h"
33 #include "sysemu/device_tree.h"
34 #include "kvm_ppc.h"
35 
36 #include "hw/ppc/spapr.h"
37 #include "hw/ppc/spapr_vio.h"
38 #include "hw/ppc/xics.h"
39 #include "hw/ppc/fdt.h"
40 #include "trace.h"
41 
42 #include <libfdt.h>
43 
44 static Property spapr_vio_props[] = {
45     DEFINE_PROP_UINT32("irq", VIOsPAPRDevice, irq, 0), \
46     DEFINE_PROP_END_OF_LIST(),
47 };
48 
49 static char *spapr_vio_get_dev_name(DeviceState *qdev)
50 {
51     VIOsPAPRDevice *dev = VIO_SPAPR_DEVICE(qdev);
52     VIOsPAPRDeviceClass *pc = VIO_SPAPR_DEVICE_GET_CLASS(dev);
53 
54     /* Device tree style name device@reg */
55     return g_strdup_printf("%s@%x", pc->dt_name, dev->reg);
56 }
57 
58 static void spapr_vio_bus_class_init(ObjectClass *klass, void *data)
59 {
60     BusClass *k = BUS_CLASS(klass);
61 
62     k->get_dev_path = spapr_vio_get_dev_name;
63     k->get_fw_dev_path = spapr_vio_get_dev_name;
64 }
65 
66 static const TypeInfo spapr_vio_bus_info = {
67     .name = TYPE_SPAPR_VIO_BUS,
68     .parent = TYPE_BUS,
69     .class_init = spapr_vio_bus_class_init,
70     .instance_size = sizeof(VIOsPAPRBus),
71 };
72 
73 VIOsPAPRDevice *spapr_vio_find_by_reg(VIOsPAPRBus *bus, uint32_t reg)
74 {
75     BusChild *kid;
76     VIOsPAPRDevice *dev = NULL;
77 
78     QTAILQ_FOREACH(kid, &bus->bus.children, sibling) {
79         dev = (VIOsPAPRDevice *)kid->child;
80         if (dev->reg == reg) {
81             return dev;
82         }
83     }
84 
85     return NULL;
86 }
87 
88 static int vio_make_devnode(VIOsPAPRDevice *dev,
89                             void *fdt)
90 {
91     VIOsPAPRDeviceClass *pc = VIO_SPAPR_DEVICE_GET_CLASS(dev);
92     int vdevice_off, node_off, ret;
93     char *dt_name;
94 
95     vdevice_off = fdt_path_offset(fdt, "/vdevice");
96     if (vdevice_off < 0) {
97         return vdevice_off;
98     }
99 
100     dt_name = spapr_vio_get_dev_name(DEVICE(dev));
101     node_off = fdt_add_subnode(fdt, vdevice_off, dt_name);
102     g_free(dt_name);
103     if (node_off < 0) {
104         return node_off;
105     }
106 
107     ret = fdt_setprop_cell(fdt, node_off, "reg", dev->reg);
108     if (ret < 0) {
109         return ret;
110     }
111 
112     if (pc->dt_type) {
113         ret = fdt_setprop_string(fdt, node_off, "device_type",
114                                  pc->dt_type);
115         if (ret < 0) {
116             return ret;
117         }
118     }
119 
120     if (pc->dt_compatible) {
121         ret = fdt_setprop_string(fdt, node_off, "compatible",
122                                  pc->dt_compatible);
123         if (ret < 0) {
124             return ret;
125         }
126     }
127 
128     if (dev->irq) {
129         uint32_t ints_prop[2];
130 
131         spapr_dt_xics_irq(ints_prop, dev->irq, false);
132         ret = fdt_setprop(fdt, node_off, "interrupts", ints_prop,
133                           sizeof(ints_prop));
134         if (ret < 0) {
135             return ret;
136         }
137     }
138 
139     ret = spapr_tcet_dma_dt(fdt, node_off, "ibm,my-dma-window", dev->tcet);
140     if (ret < 0) {
141         return ret;
142     }
143 
144     if (pc->devnode) {
145         ret = (pc->devnode)(dev, fdt, node_off);
146         if (ret < 0) {
147             return ret;
148         }
149     }
150 
151     return node_off;
152 }
153 
154 /*
155  * CRQ handling
156  */
157 static target_ulong h_reg_crq(PowerPCCPU *cpu, sPAPRMachineState *spapr,
158                               target_ulong opcode, target_ulong *args)
159 {
160     target_ulong reg = args[0];
161     target_ulong queue_addr = args[1];
162     target_ulong queue_len = args[2];
163     VIOsPAPRDevice *dev = spapr_vio_find_by_reg(spapr->vio_bus, reg);
164 
165     if (!dev) {
166         hcall_dprintf("Unit 0x" TARGET_FMT_lx " does not exist\n", reg);
167         return H_PARAMETER;
168     }
169 
170     /* We can't grok a queue size bigger than 256M for now */
171     if (queue_len < 0x1000 || queue_len > 0x10000000) {
172         hcall_dprintf("Queue size too small or too big (0x" TARGET_FMT_lx
173                       ")\n", queue_len);
174         return H_PARAMETER;
175     }
176 
177     /* Check queue alignment */
178     if (queue_addr & 0xfff) {
179         hcall_dprintf("Queue not aligned (0x" TARGET_FMT_lx ")\n", queue_addr);
180         return H_PARAMETER;
181     }
182 
183     /* Check if device supports CRQs */
184     if (!dev->crq.SendFunc) {
185         hcall_dprintf("Device does not support CRQ\n");
186         return H_NOT_FOUND;
187     }
188 
189     /* Already a queue ? */
190     if (dev->crq.qsize) {
191         hcall_dprintf("CRQ already registered\n");
192         return H_RESOURCE;
193     }
194     dev->crq.qladdr = queue_addr;
195     dev->crq.qsize = queue_len;
196     dev->crq.qnext = 0;
197 
198     trace_spapr_vio_h_reg_crq(reg, queue_addr, queue_len);
199     return H_SUCCESS;
200 }
201 
202 static target_ulong free_crq(VIOsPAPRDevice *dev)
203 {
204     dev->crq.qladdr = 0;
205     dev->crq.qsize = 0;
206     dev->crq.qnext = 0;
207 
208     trace_spapr_vio_free_crq(dev->reg);
209 
210     return H_SUCCESS;
211 }
212 
213 static target_ulong h_free_crq(PowerPCCPU *cpu, sPAPRMachineState *spapr,
214                                target_ulong opcode, target_ulong *args)
215 {
216     target_ulong reg = args[0];
217     VIOsPAPRDevice *dev = spapr_vio_find_by_reg(spapr->vio_bus, reg);
218 
219     if (!dev) {
220         hcall_dprintf("Unit 0x" TARGET_FMT_lx " does not exist\n", reg);
221         return H_PARAMETER;
222     }
223 
224     return free_crq(dev);
225 }
226 
227 static target_ulong h_send_crq(PowerPCCPU *cpu, sPAPRMachineState *spapr,
228                                target_ulong opcode, target_ulong *args)
229 {
230     target_ulong reg = args[0];
231     target_ulong msg_hi = args[1];
232     target_ulong msg_lo = args[2];
233     VIOsPAPRDevice *dev = spapr_vio_find_by_reg(spapr->vio_bus, reg);
234     uint64_t crq_mangle[2];
235 
236     if (!dev) {
237         hcall_dprintf("Unit 0x" TARGET_FMT_lx " does not exist\n", reg);
238         return H_PARAMETER;
239     }
240     crq_mangle[0] = cpu_to_be64(msg_hi);
241     crq_mangle[1] = cpu_to_be64(msg_lo);
242 
243     if (dev->crq.SendFunc) {
244         return dev->crq.SendFunc(dev, (uint8_t *)crq_mangle);
245     }
246 
247     return H_HARDWARE;
248 }
249 
250 static target_ulong h_enable_crq(PowerPCCPU *cpu, sPAPRMachineState *spapr,
251                                  target_ulong opcode, target_ulong *args)
252 {
253     target_ulong reg = args[0];
254     VIOsPAPRDevice *dev = spapr_vio_find_by_reg(spapr->vio_bus, reg);
255 
256     if (!dev) {
257         hcall_dprintf("Unit 0x" TARGET_FMT_lx " does not exist\n", reg);
258         return H_PARAMETER;
259     }
260 
261     return 0;
262 }
263 
264 /* Returns negative error, 0 success, or positive: queue full */
265 int spapr_vio_send_crq(VIOsPAPRDevice *dev, uint8_t *crq)
266 {
267     int rc;
268     uint8_t byte;
269 
270     if (!dev->crq.qsize) {
271         error_report("spapr_vio_send_creq on uninitialized queue");
272         return -1;
273     }
274 
275     /* Maybe do a fast path for KVM just writing to the pages */
276     rc = spapr_vio_dma_read(dev, dev->crq.qladdr + dev->crq.qnext, &byte, 1);
277     if (rc) {
278         return rc;
279     }
280     if (byte != 0) {
281         return 1;
282     }
283 
284     rc = spapr_vio_dma_write(dev, dev->crq.qladdr + dev->crq.qnext + 8,
285                              &crq[8], 8);
286     if (rc) {
287         return rc;
288     }
289 
290     kvmppc_eieio();
291 
292     rc = spapr_vio_dma_write(dev, dev->crq.qladdr + dev->crq.qnext, crq, 8);
293     if (rc) {
294         return rc;
295     }
296 
297     dev->crq.qnext = (dev->crq.qnext + 16) % dev->crq.qsize;
298 
299     if (dev->signal_state & 1) {
300         qemu_irq_pulse(spapr_vio_qirq(dev));
301     }
302 
303     return 0;
304 }
305 
306 /* "quiesce" handling */
307 
308 static void spapr_vio_quiesce_one(VIOsPAPRDevice *dev)
309 {
310     if (dev->tcet) {
311         device_reset(DEVICE(dev->tcet));
312     }
313     free_crq(dev);
314 }
315 
316 void spapr_vio_set_bypass(VIOsPAPRDevice *dev, bool bypass)
317 {
318     if (!dev->tcet) {
319         return;
320     }
321 
322     memory_region_set_enabled(&dev->mrbypass, bypass);
323     memory_region_set_enabled(spapr_tce_get_iommu(dev->tcet), !bypass);
324 
325     dev->tcet->bypass = bypass;
326 }
327 
328 static void rtas_set_tce_bypass(PowerPCCPU *cpu, sPAPRMachineState *spapr,
329                                 uint32_t token,
330                                 uint32_t nargs, target_ulong args,
331                                 uint32_t nret, target_ulong rets)
332 {
333     VIOsPAPRBus *bus = spapr->vio_bus;
334     VIOsPAPRDevice *dev;
335     uint32_t unit, enable;
336 
337     if (nargs != 2) {
338         rtas_st(rets, 0, RTAS_OUT_PARAM_ERROR);
339         return;
340     }
341     unit = rtas_ld(args, 0);
342     enable = rtas_ld(args, 1);
343     dev = spapr_vio_find_by_reg(bus, unit);
344     if (!dev) {
345         rtas_st(rets, 0, RTAS_OUT_PARAM_ERROR);
346         return;
347     }
348 
349     if (!dev->tcet) {
350         rtas_st(rets, 0, RTAS_OUT_PARAM_ERROR);
351         return;
352     }
353 
354     spapr_vio_set_bypass(dev, !!enable);
355 
356     rtas_st(rets, 0, RTAS_OUT_SUCCESS);
357 }
358 
359 static void rtas_quiesce(PowerPCCPU *cpu, sPAPRMachineState *spapr,
360                          uint32_t token,
361                          uint32_t nargs, target_ulong args,
362                          uint32_t nret, target_ulong rets)
363 {
364     VIOsPAPRBus *bus = spapr->vio_bus;
365     BusChild *kid;
366     VIOsPAPRDevice *dev = NULL;
367 
368     if (nargs != 0) {
369         rtas_st(rets, 0, RTAS_OUT_PARAM_ERROR);
370         return;
371     }
372 
373     QTAILQ_FOREACH(kid, &bus->bus.children, sibling) {
374         dev = (VIOsPAPRDevice *)kid->child;
375         spapr_vio_quiesce_one(dev);
376     }
377 
378     rtas_st(rets, 0, RTAS_OUT_SUCCESS);
379 }
380 
381 static VIOsPAPRDevice *reg_conflict(VIOsPAPRDevice *dev)
382 {
383     VIOsPAPRBus *bus = SPAPR_VIO_BUS(dev->qdev.parent_bus);
384     BusChild *kid;
385     VIOsPAPRDevice *other;
386 
387     /*
388      * Check for a device other than the given one which is already
389      * using the requested address. We have to open code this because
390      * the given dev might already be in the list.
391      */
392     QTAILQ_FOREACH(kid, &bus->bus.children, sibling) {
393         other = VIO_SPAPR_DEVICE(kid->child);
394 
395         if (other != dev && other->reg == dev->reg) {
396             return other;
397         }
398     }
399 
400     return 0;
401 }
402 
403 static void spapr_vio_busdev_reset(DeviceState *qdev)
404 {
405     VIOsPAPRDevice *dev = VIO_SPAPR_DEVICE(qdev);
406     VIOsPAPRDeviceClass *pc = VIO_SPAPR_DEVICE_GET_CLASS(dev);
407 
408     /* Shut down the request queue and TCEs if necessary */
409     spapr_vio_quiesce_one(dev);
410 
411     dev->signal_state = 0;
412 
413     spapr_vio_set_bypass(dev, false);
414     if (pc->reset) {
415         pc->reset(dev);
416     }
417 }
418 
419 static void spapr_vio_busdev_realize(DeviceState *qdev, Error **errp)
420 {
421     sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
422     VIOsPAPRDevice *dev = (VIOsPAPRDevice *)qdev;
423     VIOsPAPRDeviceClass *pc = VIO_SPAPR_DEVICE_GET_CLASS(dev);
424     char *id;
425     Error *local_err = NULL;
426 
427     if (dev->reg != -1) {
428         /*
429          * Explicitly assigned address, just verify that no-one else
430          * is using it.  other mechanism). We have to open code this
431          * rather than using spapr_vio_find_by_reg() because sdev
432          * itself is already in the list.
433          */
434         VIOsPAPRDevice *other = reg_conflict(dev);
435 
436         if (other) {
437             error_setg(errp, "%s and %s devices conflict at address %#x",
438                        object_get_typename(OBJECT(qdev)),
439                        object_get_typename(OBJECT(&other->qdev)),
440                        dev->reg);
441             return;
442         }
443     } else {
444         /* Need to assign an address */
445         VIOsPAPRBus *bus = SPAPR_VIO_BUS(dev->qdev.parent_bus);
446 
447         do {
448             dev->reg = bus->next_reg++;
449         } while (reg_conflict(dev));
450     }
451 
452     /* Don't overwrite ids assigned on the command line */
453     if (!dev->qdev.id) {
454         id = spapr_vio_get_dev_name(DEVICE(dev));
455         dev->qdev.id = id;
456     }
457 
458     dev->irq = spapr_irq_alloc(spapr, dev->irq, false, &local_err);
459     if (local_err) {
460         error_propagate(errp, local_err);
461         return;
462     }
463 
464     if (pc->rtce_window_size) {
465         uint32_t liobn = SPAPR_VIO_LIOBN(dev->reg);
466 
467         memory_region_init(&dev->mrroot, OBJECT(dev), "iommu-spapr-root",
468                            ram_size);
469         memory_region_init_alias(&dev->mrbypass, OBJECT(dev),
470                                  "iommu-spapr-bypass", get_system_memory(),
471                                  0, ram_size);
472         memory_region_add_subregion_overlap(&dev->mrroot, 0, &dev->mrbypass, 1);
473         address_space_init(&dev->as, &dev->mrroot, qdev->id);
474 
475         dev->tcet = spapr_tce_new_table(qdev, liobn);
476         spapr_tce_table_enable(dev->tcet, SPAPR_TCE_PAGE_SHIFT, 0,
477                                pc->rtce_window_size >> SPAPR_TCE_PAGE_SHIFT);
478         dev->tcet->vdev = dev;
479         memory_region_add_subregion_overlap(&dev->mrroot, 0,
480                                             spapr_tce_get_iommu(dev->tcet), 2);
481     }
482 
483     pc->realize(dev, errp);
484 }
485 
486 static target_ulong h_vio_signal(PowerPCCPU *cpu, sPAPRMachineState *spapr,
487                                  target_ulong opcode,
488                                  target_ulong *args)
489 {
490     target_ulong reg = args[0];
491     target_ulong mode = args[1];
492     VIOsPAPRDevice *dev = spapr_vio_find_by_reg(spapr->vio_bus, reg);
493     VIOsPAPRDeviceClass *pc;
494 
495     if (!dev) {
496         return H_PARAMETER;
497     }
498 
499     pc = VIO_SPAPR_DEVICE_GET_CLASS(dev);
500 
501     if (mode & ~pc->signal_mask) {
502         return H_PARAMETER;
503     }
504 
505     dev->signal_state = mode;
506 
507     return H_SUCCESS;
508 }
509 
510 VIOsPAPRBus *spapr_vio_bus_init(void)
511 {
512     VIOsPAPRBus *bus;
513     BusState *qbus;
514     DeviceState *dev;
515 
516     /* Create bridge device */
517     dev = qdev_create(NULL, TYPE_SPAPR_VIO_BRIDGE);
518     qdev_init_nofail(dev);
519 
520     /* Create bus on bridge device */
521     qbus = qbus_create(TYPE_SPAPR_VIO_BUS, dev, "spapr-vio");
522     bus = SPAPR_VIO_BUS(qbus);
523     bus->next_reg = 0x71000000;
524 
525     /* hcall-vio */
526     spapr_register_hypercall(H_VIO_SIGNAL, h_vio_signal);
527 
528     /* hcall-crq */
529     spapr_register_hypercall(H_REG_CRQ, h_reg_crq);
530     spapr_register_hypercall(H_FREE_CRQ, h_free_crq);
531     spapr_register_hypercall(H_SEND_CRQ, h_send_crq);
532     spapr_register_hypercall(H_ENABLE_CRQ, h_enable_crq);
533 
534     /* RTAS calls */
535     spapr_rtas_register(RTAS_IBM_SET_TCE_BYPASS, "ibm,set-tce-bypass",
536                         rtas_set_tce_bypass);
537     spapr_rtas_register(RTAS_QUIESCE, "quiesce", rtas_quiesce);
538 
539     return bus;
540 }
541 
542 static void spapr_vio_bridge_class_init(ObjectClass *klass, void *data)
543 {
544     DeviceClass *dc = DEVICE_CLASS(klass);
545 
546     dc->fw_name = "vdevice";
547 }
548 
549 static const TypeInfo spapr_vio_bridge_info = {
550     .name          = TYPE_SPAPR_VIO_BRIDGE,
551     .parent        = TYPE_SYS_BUS_DEVICE,
552     .class_init    = spapr_vio_bridge_class_init,
553 };
554 
555 const VMStateDescription vmstate_spapr_vio = {
556     .name = "spapr_vio",
557     .version_id = 1,
558     .minimum_version_id = 1,
559     .fields = (VMStateField[]) {
560         /* Sanity check */
561         VMSTATE_UINT32_EQUAL(reg, VIOsPAPRDevice, NULL),
562         VMSTATE_UINT32_EQUAL(irq, VIOsPAPRDevice, NULL),
563 
564         /* General VIO device state */
565         VMSTATE_UINT64(signal_state, VIOsPAPRDevice),
566         VMSTATE_UINT64(crq.qladdr, VIOsPAPRDevice),
567         VMSTATE_UINT32(crq.qsize, VIOsPAPRDevice),
568         VMSTATE_UINT32(crq.qnext, VIOsPAPRDevice),
569 
570         VMSTATE_END_OF_LIST()
571     },
572 };
573 
574 static void vio_spapr_device_class_init(ObjectClass *klass, void *data)
575 {
576     DeviceClass *k = DEVICE_CLASS(klass);
577     k->realize = spapr_vio_busdev_realize;
578     k->reset = spapr_vio_busdev_reset;
579     k->bus_type = TYPE_SPAPR_VIO_BUS;
580     k->props = spapr_vio_props;
581 }
582 
583 static const TypeInfo spapr_vio_type_info = {
584     .name = TYPE_VIO_SPAPR_DEVICE,
585     .parent = TYPE_DEVICE,
586     .instance_size = sizeof(VIOsPAPRDevice),
587     .abstract = true,
588     .class_size = sizeof(VIOsPAPRDeviceClass),
589     .class_init = vio_spapr_device_class_init,
590 };
591 
592 static void spapr_vio_register_types(void)
593 {
594     type_register_static(&spapr_vio_bus_info);
595     type_register_static(&spapr_vio_bridge_info);
596     type_register_static(&spapr_vio_type_info);
597 }
598 
599 type_init(spapr_vio_register_types)
600 
601 static int compare_reg(const void *p1, const void *p2)
602 {
603     VIOsPAPRDevice const *dev1, *dev2;
604 
605     dev1 = (VIOsPAPRDevice *)*(DeviceState **)p1;
606     dev2 = (VIOsPAPRDevice *)*(DeviceState **)p2;
607 
608     if (dev1->reg < dev2->reg) {
609         return -1;
610     }
611     if (dev1->reg == dev2->reg) {
612         return 0;
613     }
614 
615     /* dev1->reg > dev2->reg */
616     return 1;
617 }
618 
619 void spapr_dt_vdevice(VIOsPAPRBus *bus, void *fdt)
620 {
621     DeviceState *qdev, **qdevs;
622     BusChild *kid;
623     int i, num, ret = 0;
624     int node;
625 
626     _FDT(node = fdt_add_subnode(fdt, 0, "vdevice"));
627 
628     _FDT(fdt_setprop_string(fdt, node, "device_type", "vdevice"));
629     _FDT(fdt_setprop_string(fdt, node, "compatible", "IBM,vdevice"));
630     _FDT(fdt_setprop_cell(fdt, node, "#address-cells", 1));
631     _FDT(fdt_setprop_cell(fdt, node, "#size-cells", 0));
632     _FDT(fdt_setprop_cell(fdt, node, "#interrupt-cells", 2));
633     _FDT(fdt_setprop(fdt, node, "interrupt-controller", NULL, 0));
634 
635     /* Count qdevs on the bus list */
636     num = 0;
637     QTAILQ_FOREACH(kid, &bus->bus.children, sibling) {
638         num++;
639     }
640 
641     /* Copy out into an array of pointers */
642     qdevs = g_malloc(sizeof(qdev) * num);
643     num = 0;
644     QTAILQ_FOREACH(kid, &bus->bus.children, sibling) {
645         qdevs[num++] = kid->child;
646     }
647 
648     /* Sort the array */
649     qsort(qdevs, num, sizeof(qdev), compare_reg);
650 
651     /* Hack alert. Give the devices to libfdt in reverse order, we happen
652      * to know that will mean they are in forward order in the tree. */
653     for (i = num - 1; i >= 0; i--) {
654         VIOsPAPRDevice *dev = (VIOsPAPRDevice *)(qdevs[i]);
655         VIOsPAPRDeviceClass *vdc = VIO_SPAPR_DEVICE_GET_CLASS(dev);
656 
657         ret = vio_make_devnode(dev, fdt);
658         if (ret < 0) {
659             error_report("Couldn't create device node /vdevice/%s@%"PRIx32,
660                          vdc->dt_name, dev->reg);
661             exit(1);
662         }
663     }
664 
665     g_free(qdevs);
666 }
667 
668 gchar *spapr_vio_stdout_path(VIOsPAPRBus *bus)
669 {
670     VIOsPAPRDevice *dev;
671     char *name, *path;
672 
673     dev = spapr_vty_get_default(bus);
674     if (!dev) {
675         return NULL;
676     }
677 
678     name = spapr_vio_get_dev_name(DEVICE(dev));
679     path = g_strdup_printf("/vdevice/%s", name);
680 
681     g_free(name);
682     return path;
683 }
684