xref: /openbmc/qemu/hw/ppc/spapr_vio.c (revision a9ded601)
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[] = {cpu_to_be32(dev->irq), 0};
130 
131         ret = fdt_setprop(fdt, node_off, "interrupts", ints_prop,
132                           sizeof(ints_prop));
133         if (ret < 0) {
134             return ret;
135         }
136     }
137 
138     ret = spapr_tcet_dma_dt(fdt, node_off, "ibm,my-dma-window", dev->tcet);
139     if (ret < 0) {
140         return ret;
141     }
142 
143     if (pc->devnode) {
144         ret = (pc->devnode)(dev, fdt, node_off);
145         if (ret < 0) {
146             return ret;
147         }
148     }
149 
150     return node_off;
151 }
152 
153 /*
154  * CRQ handling
155  */
156 static target_ulong h_reg_crq(PowerPCCPU *cpu, sPAPRMachineState *spapr,
157                               target_ulong opcode, target_ulong *args)
158 {
159     target_ulong reg = args[0];
160     target_ulong queue_addr = args[1];
161     target_ulong queue_len = args[2];
162     VIOsPAPRDevice *dev = spapr_vio_find_by_reg(spapr->vio_bus, reg);
163 
164     if (!dev) {
165         hcall_dprintf("Unit 0x" TARGET_FMT_lx " does not exist\n", reg);
166         return H_PARAMETER;
167     }
168 
169     /* We can't grok a queue size bigger than 256M for now */
170     if (queue_len < 0x1000 || queue_len > 0x10000000) {
171         hcall_dprintf("Queue size too small or too big (0x" TARGET_FMT_lx
172                       ")\n", queue_len);
173         return H_PARAMETER;
174     }
175 
176     /* Check queue alignment */
177     if (queue_addr & 0xfff) {
178         hcall_dprintf("Queue not aligned (0x" TARGET_FMT_lx ")\n", queue_addr);
179         return H_PARAMETER;
180     }
181 
182     /* Check if device supports CRQs */
183     if (!dev->crq.SendFunc) {
184         hcall_dprintf("Device does not support CRQ\n");
185         return H_NOT_FOUND;
186     }
187 
188     /* Already a queue ? */
189     if (dev->crq.qsize) {
190         hcall_dprintf("CRQ already registered\n");
191         return H_RESOURCE;
192     }
193     dev->crq.qladdr = queue_addr;
194     dev->crq.qsize = queue_len;
195     dev->crq.qnext = 0;
196 
197     trace_spapr_vio_h_reg_crq(reg, queue_addr, queue_len);
198     return H_SUCCESS;
199 }
200 
201 static target_ulong free_crq(VIOsPAPRDevice *dev)
202 {
203     dev->crq.qladdr = 0;
204     dev->crq.qsize = 0;
205     dev->crq.qnext = 0;
206 
207     trace_spapr_vio_free_crq(dev->reg);
208 
209     return H_SUCCESS;
210 }
211 
212 static target_ulong h_free_crq(PowerPCCPU *cpu, sPAPRMachineState *spapr,
213                                target_ulong opcode, target_ulong *args)
214 {
215     target_ulong reg = args[0];
216     VIOsPAPRDevice *dev = spapr_vio_find_by_reg(spapr->vio_bus, reg);
217 
218     if (!dev) {
219         hcall_dprintf("Unit 0x" TARGET_FMT_lx " does not exist\n", reg);
220         return H_PARAMETER;
221     }
222 
223     return free_crq(dev);
224 }
225 
226 static target_ulong h_send_crq(PowerPCCPU *cpu, sPAPRMachineState *spapr,
227                                target_ulong opcode, target_ulong *args)
228 {
229     target_ulong reg = args[0];
230     target_ulong msg_hi = args[1];
231     target_ulong msg_lo = args[2];
232     VIOsPAPRDevice *dev = spapr_vio_find_by_reg(spapr->vio_bus, reg);
233     uint64_t crq_mangle[2];
234 
235     if (!dev) {
236         hcall_dprintf("Unit 0x" TARGET_FMT_lx " does not exist\n", reg);
237         return H_PARAMETER;
238     }
239     crq_mangle[0] = cpu_to_be64(msg_hi);
240     crq_mangle[1] = cpu_to_be64(msg_lo);
241 
242     if (dev->crq.SendFunc) {
243         return dev->crq.SendFunc(dev, (uint8_t *)crq_mangle);
244     }
245 
246     return H_HARDWARE;
247 }
248 
249 static target_ulong h_enable_crq(PowerPCCPU *cpu, sPAPRMachineState *spapr,
250                                  target_ulong opcode, target_ulong *args)
251 {
252     target_ulong reg = args[0];
253     VIOsPAPRDevice *dev = spapr_vio_find_by_reg(spapr->vio_bus, reg);
254 
255     if (!dev) {
256         hcall_dprintf("Unit 0x" TARGET_FMT_lx " does not exist\n", reg);
257         return H_PARAMETER;
258     }
259 
260     return 0;
261 }
262 
263 /* Returns negative error, 0 success, or positive: queue full */
264 int spapr_vio_send_crq(VIOsPAPRDevice *dev, uint8_t *crq)
265 {
266     int rc;
267     uint8_t byte;
268 
269     if (!dev->crq.qsize) {
270         error_report("spapr_vio_send_creq on uninitialized queue");
271         return -1;
272     }
273 
274     /* Maybe do a fast path for KVM just writing to the pages */
275     rc = spapr_vio_dma_read(dev, dev->crq.qladdr + dev->crq.qnext, &byte, 1);
276     if (rc) {
277         return rc;
278     }
279     if (byte != 0) {
280         return 1;
281     }
282 
283     rc = spapr_vio_dma_write(dev, dev->crq.qladdr + dev->crq.qnext + 8,
284                              &crq[8], 8);
285     if (rc) {
286         return rc;
287     }
288 
289     kvmppc_eieio();
290 
291     rc = spapr_vio_dma_write(dev, dev->crq.qladdr + dev->crq.qnext, crq, 8);
292     if (rc) {
293         return rc;
294     }
295 
296     dev->crq.qnext = (dev->crq.qnext + 16) % dev->crq.qsize;
297 
298     if (dev->signal_state & 1) {
299         qemu_irq_pulse(spapr_vio_qirq(dev));
300     }
301 
302     return 0;
303 }
304 
305 /* "quiesce" handling */
306 
307 static void spapr_vio_quiesce_one(VIOsPAPRDevice *dev)
308 {
309     if (dev->tcet) {
310         device_reset(DEVICE(dev->tcet));
311     }
312     free_crq(dev);
313 }
314 
315 void spapr_vio_set_bypass(VIOsPAPRDevice *dev, bool bypass)
316 {
317     if (!dev->tcet) {
318         return;
319     }
320 
321     memory_region_set_enabled(&dev->mrbypass, bypass);
322     memory_region_set_enabled(spapr_tce_get_iommu(dev->tcet), !bypass);
323 
324     dev->tcet->bypass = bypass;
325 }
326 
327 static void rtas_set_tce_bypass(PowerPCCPU *cpu, sPAPRMachineState *spapr,
328                                 uint32_t token,
329                                 uint32_t nargs, target_ulong args,
330                                 uint32_t nret, target_ulong rets)
331 {
332     VIOsPAPRBus *bus = spapr->vio_bus;
333     VIOsPAPRDevice *dev;
334     uint32_t unit, enable;
335 
336     if (nargs != 2) {
337         rtas_st(rets, 0, RTAS_OUT_PARAM_ERROR);
338         return;
339     }
340     unit = rtas_ld(args, 0);
341     enable = rtas_ld(args, 1);
342     dev = spapr_vio_find_by_reg(bus, unit);
343     if (!dev) {
344         rtas_st(rets, 0, RTAS_OUT_PARAM_ERROR);
345         return;
346     }
347 
348     if (!dev->tcet) {
349         rtas_st(rets, 0, RTAS_OUT_PARAM_ERROR);
350         return;
351     }
352 
353     spapr_vio_set_bypass(dev, !!enable);
354 
355     rtas_st(rets, 0, RTAS_OUT_SUCCESS);
356 }
357 
358 static void rtas_quiesce(PowerPCCPU *cpu, sPAPRMachineState *spapr,
359                          uint32_t token,
360                          uint32_t nargs, target_ulong args,
361                          uint32_t nret, target_ulong rets)
362 {
363     VIOsPAPRBus *bus = spapr->vio_bus;
364     BusChild *kid;
365     VIOsPAPRDevice *dev = NULL;
366 
367     if (nargs != 0) {
368         rtas_st(rets, 0, RTAS_OUT_PARAM_ERROR);
369         return;
370     }
371 
372     QTAILQ_FOREACH(kid, &bus->bus.children, sibling) {
373         dev = (VIOsPAPRDevice *)kid->child;
374         spapr_vio_quiesce_one(dev);
375     }
376 
377     rtas_st(rets, 0, RTAS_OUT_SUCCESS);
378 }
379 
380 static VIOsPAPRDevice *reg_conflict(VIOsPAPRDevice *dev)
381 {
382     VIOsPAPRBus *bus = SPAPR_VIO_BUS(dev->qdev.parent_bus);
383     BusChild *kid;
384     VIOsPAPRDevice *other;
385 
386     /*
387      * Check for a device other than the given one which is already
388      * using the requested address. We have to open code this because
389      * the given dev might already be in the list.
390      */
391     QTAILQ_FOREACH(kid, &bus->bus.children, sibling) {
392         other = VIO_SPAPR_DEVICE(kid->child);
393 
394         if (other != dev && other->reg == dev->reg) {
395             return other;
396         }
397     }
398 
399     return 0;
400 }
401 
402 static void spapr_vio_busdev_reset(DeviceState *qdev)
403 {
404     VIOsPAPRDevice *dev = VIO_SPAPR_DEVICE(qdev);
405     VIOsPAPRDeviceClass *pc = VIO_SPAPR_DEVICE_GET_CLASS(dev);
406 
407     /* Shut down the request queue and TCEs if necessary */
408     spapr_vio_quiesce_one(dev);
409 
410     dev->signal_state = 0;
411 
412     spapr_vio_set_bypass(dev, false);
413     if (pc->reset) {
414         pc->reset(dev);
415     }
416 }
417 
418 static void spapr_vio_busdev_realize(DeviceState *qdev, Error **errp)
419 {
420     sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
421     VIOsPAPRDevice *dev = (VIOsPAPRDevice *)qdev;
422     VIOsPAPRDeviceClass *pc = VIO_SPAPR_DEVICE_GET_CLASS(dev);
423     char *id;
424     Error *local_err = NULL;
425 
426     if (dev->reg != -1) {
427         /*
428          * Explicitly assigned address, just verify that no-one else
429          * is using it.  other mechanism). We have to open code this
430          * rather than using spapr_vio_find_by_reg() because sdev
431          * itself is already in the list.
432          */
433         VIOsPAPRDevice *other = reg_conflict(dev);
434 
435         if (other) {
436             error_setg(errp, "%s and %s devices conflict at address %#x",
437                        object_get_typename(OBJECT(qdev)),
438                        object_get_typename(OBJECT(&other->qdev)),
439                        dev->reg);
440             return;
441         }
442     } else {
443         /* Need to assign an address */
444         VIOsPAPRBus *bus = SPAPR_VIO_BUS(dev->qdev.parent_bus);
445 
446         do {
447             dev->reg = bus->next_reg++;
448         } while (reg_conflict(dev));
449     }
450 
451     /* Don't overwrite ids assigned on the command line */
452     if (!dev->qdev.id) {
453         id = spapr_vio_get_dev_name(DEVICE(dev));
454         dev->qdev.id = id;
455     }
456 
457     dev->irq = spapr_ics_alloc(spapr->ics, dev->irq, false, &local_err);
458     if (local_err) {
459         error_propagate(errp, local_err);
460         return;
461     }
462 
463     if (pc->rtce_window_size) {
464         uint32_t liobn = SPAPR_VIO_LIOBN(dev->reg);
465 
466         memory_region_init(&dev->mrroot, OBJECT(dev), "iommu-spapr-root",
467                            ram_size);
468         memory_region_init_alias(&dev->mrbypass, OBJECT(dev),
469                                  "iommu-spapr-bypass", get_system_memory(),
470                                  0, ram_size);
471         memory_region_add_subregion_overlap(&dev->mrroot, 0, &dev->mrbypass, 1);
472         address_space_init(&dev->as, &dev->mrroot, qdev->id);
473 
474         dev->tcet = spapr_tce_new_table(qdev, liobn);
475         spapr_tce_table_enable(dev->tcet, SPAPR_TCE_PAGE_SHIFT, 0,
476                                pc->rtce_window_size >> SPAPR_TCE_PAGE_SHIFT);
477         dev->tcet->vdev = dev;
478         memory_region_add_subregion_overlap(&dev->mrroot, 0,
479                                             spapr_tce_get_iommu(dev->tcet), 2);
480     }
481 
482     pc->realize(dev, errp);
483 }
484 
485 static target_ulong h_vio_signal(PowerPCCPU *cpu, sPAPRMachineState *spapr,
486                                  target_ulong opcode,
487                                  target_ulong *args)
488 {
489     target_ulong reg = args[0];
490     target_ulong mode = args[1];
491     VIOsPAPRDevice *dev = spapr_vio_find_by_reg(spapr->vio_bus, reg);
492     VIOsPAPRDeviceClass *pc;
493 
494     if (!dev) {
495         return H_PARAMETER;
496     }
497 
498     pc = VIO_SPAPR_DEVICE_GET_CLASS(dev);
499 
500     if (mode & ~pc->signal_mask) {
501         return H_PARAMETER;
502     }
503 
504     dev->signal_state = mode;
505 
506     return H_SUCCESS;
507 }
508 
509 VIOsPAPRBus *spapr_vio_bus_init(void)
510 {
511     VIOsPAPRBus *bus;
512     BusState *qbus;
513     DeviceState *dev;
514 
515     /* Create bridge device */
516     dev = qdev_create(NULL, TYPE_SPAPR_VIO_BRIDGE);
517     qdev_init_nofail(dev);
518 
519     /* Create bus on bridge device */
520     qbus = qbus_create(TYPE_SPAPR_VIO_BUS, dev, "spapr-vio");
521     bus = SPAPR_VIO_BUS(qbus);
522     bus->next_reg = 0x71000000;
523 
524     /* hcall-vio */
525     spapr_register_hypercall(H_VIO_SIGNAL, h_vio_signal);
526 
527     /* hcall-crq */
528     spapr_register_hypercall(H_REG_CRQ, h_reg_crq);
529     spapr_register_hypercall(H_FREE_CRQ, h_free_crq);
530     spapr_register_hypercall(H_SEND_CRQ, h_send_crq);
531     spapr_register_hypercall(H_ENABLE_CRQ, h_enable_crq);
532 
533     /* RTAS calls */
534     spapr_rtas_register(RTAS_IBM_SET_TCE_BYPASS, "ibm,set-tce-bypass",
535                         rtas_set_tce_bypass);
536     spapr_rtas_register(RTAS_QUIESCE, "quiesce", rtas_quiesce);
537 
538     return bus;
539 }
540 
541 static void spapr_vio_bridge_class_init(ObjectClass *klass, void *data)
542 {
543     DeviceClass *dc = DEVICE_CLASS(klass);
544 
545     dc->fw_name = "vdevice";
546 }
547 
548 static const TypeInfo spapr_vio_bridge_info = {
549     .name          = TYPE_SPAPR_VIO_BRIDGE,
550     .parent        = TYPE_SYS_BUS_DEVICE,
551     .class_init    = spapr_vio_bridge_class_init,
552 };
553 
554 const VMStateDescription vmstate_spapr_vio = {
555     .name = "spapr_vio",
556     .version_id = 1,
557     .minimum_version_id = 1,
558     .fields = (VMStateField[]) {
559         /* Sanity check */
560         VMSTATE_UINT32_EQUAL(reg, VIOsPAPRDevice),
561         VMSTATE_UINT32_EQUAL(irq, VIOsPAPRDevice),
562 
563         /* General VIO device state */
564         VMSTATE_UINT64(signal_state, VIOsPAPRDevice),
565         VMSTATE_UINT64(crq.qladdr, VIOsPAPRDevice),
566         VMSTATE_UINT32(crq.qsize, VIOsPAPRDevice),
567         VMSTATE_UINT32(crq.qnext, VIOsPAPRDevice),
568 
569         VMSTATE_END_OF_LIST()
570     },
571 };
572 
573 static void vio_spapr_device_class_init(ObjectClass *klass, void *data)
574 {
575     DeviceClass *k = DEVICE_CLASS(klass);
576     k->realize = spapr_vio_busdev_realize;
577     k->reset = spapr_vio_busdev_reset;
578     k->bus_type = TYPE_SPAPR_VIO_BUS;
579     k->props = spapr_vio_props;
580 }
581 
582 static const TypeInfo spapr_vio_type_info = {
583     .name = TYPE_VIO_SPAPR_DEVICE,
584     .parent = TYPE_DEVICE,
585     .instance_size = sizeof(VIOsPAPRDevice),
586     .abstract = true,
587     .class_size = sizeof(VIOsPAPRDeviceClass),
588     .class_init = vio_spapr_device_class_init,
589 };
590 
591 static void spapr_vio_register_types(void)
592 {
593     type_register_static(&spapr_vio_bus_info);
594     type_register_static(&spapr_vio_bridge_info);
595     type_register_static(&spapr_vio_type_info);
596 }
597 
598 type_init(spapr_vio_register_types)
599 
600 static int compare_reg(const void *p1, const void *p2)
601 {
602     VIOsPAPRDevice const *dev1, *dev2;
603 
604     dev1 = (VIOsPAPRDevice *)*(DeviceState **)p1;
605     dev2 = (VIOsPAPRDevice *)*(DeviceState **)p2;
606 
607     if (dev1->reg < dev2->reg) {
608         return -1;
609     }
610     if (dev1->reg == dev2->reg) {
611         return 0;
612     }
613 
614     /* dev1->reg > dev2->reg */
615     return 1;
616 }
617 
618 void spapr_dt_vdevice(VIOsPAPRBus *bus, void *fdt)
619 {
620     DeviceState *qdev, **qdevs;
621     BusChild *kid;
622     int i, num, ret = 0;
623     int node;
624 
625     _FDT(node = fdt_add_subnode(fdt, 0, "vdevice"));
626 
627     _FDT(fdt_setprop_string(fdt, node, "device_type", "vdevice"));
628     _FDT(fdt_setprop_string(fdt, node, "compatible", "IBM,vdevice"));
629     _FDT(fdt_setprop_cell(fdt, node, "#address-cells", 1));
630     _FDT(fdt_setprop_cell(fdt, node, "#size-cells", 0));
631     _FDT(fdt_setprop_cell(fdt, node, "#interrupt-cells", 2));
632     _FDT(fdt_setprop(fdt, node, "interrupt-controller", NULL, 0));
633 
634     /* Count qdevs on the bus list */
635     num = 0;
636     QTAILQ_FOREACH(kid, &bus->bus.children, sibling) {
637         num++;
638     }
639 
640     /* Copy out into an array of pointers */
641     qdevs = g_malloc(sizeof(qdev) * num);
642     num = 0;
643     QTAILQ_FOREACH(kid, &bus->bus.children, sibling) {
644         qdevs[num++] = kid->child;
645     }
646 
647     /* Sort the array */
648     qsort(qdevs, num, sizeof(qdev), compare_reg);
649 
650     /* Hack alert. Give the devices to libfdt in reverse order, we happen
651      * to know that will mean they are in forward order in the tree. */
652     for (i = num - 1; i >= 0; i--) {
653         VIOsPAPRDevice *dev = (VIOsPAPRDevice *)(qdevs[i]);
654         VIOsPAPRDeviceClass *vdc = VIO_SPAPR_DEVICE_GET_CLASS(dev);
655 
656         ret = vio_make_devnode(dev, fdt);
657         if (ret < 0) {
658             error_report("Couldn't create device node /vdevice/%s@%"PRIx32,
659                          vdc->dt_name, dev->reg);
660             exit(1);
661         }
662     }
663 
664     g_free(qdevs);
665 }
666 
667 gchar *spapr_vio_stdout_path(VIOsPAPRBus *bus)
668 {
669     VIOsPAPRDevice *dev;
670     char *name, *path;
671 
672     dev = spapr_vty_get_default(bus);
673     if (!dev) {
674         return NULL;
675     }
676 
677     name = spapr_vio_get_dev_name(DEVICE(dev));
678     path = g_strdup_printf("/vdevice/%s", name);
679 
680     g_free(name);
681     return path;
682 }
683