xref: /openbmc/qemu/hw/ppc/spapr_vio.c (revision 84a3a53c)
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 "hw/hw.h"
23 #include "sysemu/sysemu.h"
24 #include "hw/boards.h"
25 #include "hw/loader.h"
26 #include "elf.h"
27 #include "hw/sysbus.h"
28 #include "sysemu/kvm.h"
29 #include "sysemu/device_tree.h"
30 #include "kvm_ppc.h"
31 
32 #include "hw/ppc/spapr.h"
33 #include "hw/ppc/spapr_vio.h"
34 #include "hw/ppc/xics.h"
35 
36 #include <libfdt.h>
37 
38 /* #define DEBUG_SPAPR */
39 
40 #ifdef DEBUG_SPAPR
41 #define DPRINTF(fmt, ...) \
42     do { fprintf(stderr, fmt, ## __VA_ARGS__); } while (0)
43 #else
44 #define DPRINTF(fmt, ...) \
45     do { } while (0)
46 #endif
47 
48 static Property spapr_vio_props[] = {
49     DEFINE_PROP_UINT32("irq", VIOsPAPRDevice, irq, 0), \
50     DEFINE_PROP_END_OF_LIST(),
51 };
52 
53 static char *spapr_vio_get_dev_name(DeviceState *qdev)
54 {
55     VIOsPAPRDevice *dev = VIO_SPAPR_DEVICE(qdev);
56     VIOsPAPRDeviceClass *pc = VIO_SPAPR_DEVICE_GET_CLASS(dev);
57     char *name;
58 
59     /* Device tree style name device@reg */
60     name = g_strdup_printf("%s@%x", pc->dt_name, dev->reg);
61 
62     return name;
63 }
64 
65 static void spapr_vio_bus_class_init(ObjectClass *klass, void *data)
66 {
67     BusClass *k = BUS_CLASS(klass);
68 
69     k->get_dev_path = spapr_vio_get_dev_name;
70     k->get_fw_dev_path = spapr_vio_get_dev_name;
71 }
72 
73 static const TypeInfo spapr_vio_bus_info = {
74     .name = TYPE_SPAPR_VIO_BUS,
75     .parent = TYPE_BUS,
76     .class_init = spapr_vio_bus_class_init,
77     .instance_size = sizeof(VIOsPAPRBus),
78 };
79 
80 VIOsPAPRDevice *spapr_vio_find_by_reg(VIOsPAPRBus *bus, uint32_t reg)
81 {
82     BusChild *kid;
83     VIOsPAPRDevice *dev = NULL;
84 
85     QTAILQ_FOREACH(kid, &bus->bus.children, sibling) {
86         dev = (VIOsPAPRDevice *)kid->child;
87         if (dev->reg == reg) {
88             return dev;
89         }
90     }
91 
92     return NULL;
93 }
94 
95 static int vio_make_devnode(VIOsPAPRDevice *dev,
96                             void *fdt)
97 {
98     VIOsPAPRDeviceClass *pc = VIO_SPAPR_DEVICE_GET_CLASS(dev);
99     int vdevice_off, node_off, ret;
100     char *dt_name;
101 
102     vdevice_off = fdt_path_offset(fdt, "/vdevice");
103     if (vdevice_off < 0) {
104         return vdevice_off;
105     }
106 
107     dt_name = spapr_vio_get_dev_name(DEVICE(dev));
108     node_off = fdt_add_subnode(fdt, vdevice_off, dt_name);
109     g_free(dt_name);
110     if (node_off < 0) {
111         return node_off;
112     }
113 
114     ret = fdt_setprop_cell(fdt, node_off, "reg", dev->reg);
115     if (ret < 0) {
116         return ret;
117     }
118 
119     if (pc->dt_type) {
120         ret = fdt_setprop_string(fdt, node_off, "device_type",
121                                  pc->dt_type);
122         if (ret < 0) {
123             return ret;
124         }
125     }
126 
127     if (pc->dt_compatible) {
128         ret = fdt_setprop_string(fdt, node_off, "compatible",
129                                  pc->dt_compatible);
130         if (ret < 0) {
131             return ret;
132         }
133     }
134 
135     if (dev->irq) {
136         uint32_t ints_prop[] = {cpu_to_be32(dev->irq), 0};
137 
138         ret = fdt_setprop(fdt, node_off, "interrupts", ints_prop,
139                           sizeof(ints_prop));
140         if (ret < 0) {
141             return ret;
142         }
143     }
144 
145     ret = spapr_tcet_dma_dt(fdt, node_off, "ibm,my-dma-window", dev->tcet);
146     if (ret < 0) {
147         return ret;
148     }
149 
150     if (pc->devnode) {
151         ret = (pc->devnode)(dev, fdt, node_off);
152         if (ret < 0) {
153             return ret;
154         }
155     }
156 
157     return node_off;
158 }
159 
160 /*
161  * CRQ handling
162  */
163 static target_ulong h_reg_crq(PowerPCCPU *cpu, sPAPRMachineState *spapr,
164                               target_ulong opcode, target_ulong *args)
165 {
166     target_ulong reg = args[0];
167     target_ulong queue_addr = args[1];
168     target_ulong queue_len = args[2];
169     VIOsPAPRDevice *dev = spapr_vio_find_by_reg(spapr->vio_bus, reg);
170 
171     if (!dev) {
172         hcall_dprintf("Unit 0x" TARGET_FMT_lx " does not exist\n", reg);
173         return H_PARAMETER;
174     }
175 
176     /* We can't grok a queue size bigger than 256M for now */
177     if (queue_len < 0x1000 || queue_len > 0x10000000) {
178         hcall_dprintf("Queue size too small or too big (0x" TARGET_FMT_lx
179                       ")\n", queue_len);
180         return H_PARAMETER;
181     }
182 
183     /* Check queue alignment */
184     if (queue_addr & 0xfff) {
185         hcall_dprintf("Queue not aligned (0x" TARGET_FMT_lx ")\n", queue_addr);
186         return H_PARAMETER;
187     }
188 
189     /* Check if device supports CRQs */
190     if (!dev->crq.SendFunc) {
191         hcall_dprintf("Device does not support CRQ\n");
192         return H_NOT_FOUND;
193     }
194 
195     /* Already a queue ? */
196     if (dev->crq.qsize) {
197         hcall_dprintf("CRQ already registered\n");
198         return H_RESOURCE;
199     }
200     dev->crq.qladdr = queue_addr;
201     dev->crq.qsize = queue_len;
202     dev->crq.qnext = 0;
203 
204     DPRINTF("CRQ for dev 0x" TARGET_FMT_lx " registered at 0x"
205             TARGET_FMT_lx "/0x" TARGET_FMT_lx "\n",
206             reg, queue_addr, queue_len);
207     return H_SUCCESS;
208 }
209 
210 static target_ulong free_crq(VIOsPAPRDevice *dev)
211 {
212     dev->crq.qladdr = 0;
213     dev->crq.qsize = 0;
214     dev->crq.qnext = 0;
215 
216     DPRINTF("CRQ for dev 0x%" PRIx32 " freed\n", dev->reg);
217 
218     return H_SUCCESS;
219 }
220 
221 static target_ulong h_free_crq(PowerPCCPU *cpu, sPAPRMachineState *spapr,
222                                target_ulong opcode, target_ulong *args)
223 {
224     target_ulong reg = args[0];
225     VIOsPAPRDevice *dev = spapr_vio_find_by_reg(spapr->vio_bus, reg);
226 
227     if (!dev) {
228         hcall_dprintf("Unit 0x" TARGET_FMT_lx " does not exist\n", reg);
229         return H_PARAMETER;
230     }
231 
232     return free_crq(dev);
233 }
234 
235 static target_ulong h_send_crq(PowerPCCPU *cpu, sPAPRMachineState *spapr,
236                                target_ulong opcode, target_ulong *args)
237 {
238     target_ulong reg = args[0];
239     target_ulong msg_hi = args[1];
240     target_ulong msg_lo = args[2];
241     VIOsPAPRDevice *dev = spapr_vio_find_by_reg(spapr->vio_bus, reg);
242     uint64_t crq_mangle[2];
243 
244     if (!dev) {
245         hcall_dprintf("Unit 0x" TARGET_FMT_lx " does not exist\n", reg);
246         return H_PARAMETER;
247     }
248     crq_mangle[0] = cpu_to_be64(msg_hi);
249     crq_mangle[1] = cpu_to_be64(msg_lo);
250 
251     if (dev->crq.SendFunc) {
252         return dev->crq.SendFunc(dev, (uint8_t *)crq_mangle);
253     }
254 
255     return H_HARDWARE;
256 }
257 
258 static target_ulong h_enable_crq(PowerPCCPU *cpu, sPAPRMachineState *spapr,
259                                  target_ulong opcode, target_ulong *args)
260 {
261     target_ulong reg = args[0];
262     VIOsPAPRDevice *dev = spapr_vio_find_by_reg(spapr->vio_bus, reg);
263 
264     if (!dev) {
265         hcall_dprintf("Unit 0x" TARGET_FMT_lx " does not exist\n", reg);
266         return H_PARAMETER;
267     }
268 
269     return 0;
270 }
271 
272 /* Returns negative error, 0 success, or positive: queue full */
273 int spapr_vio_send_crq(VIOsPAPRDevice *dev, uint8_t *crq)
274 {
275     int rc;
276     uint8_t byte;
277 
278     if (!dev->crq.qsize) {
279         fprintf(stderr, "spapr_vio_send_creq on uninitialized queue\n");
280         return -1;
281     }
282 
283     /* Maybe do a fast path for KVM just writing to the pages */
284     rc = spapr_vio_dma_read(dev, dev->crq.qladdr + dev->crq.qnext, &byte, 1);
285     if (rc) {
286         return rc;
287     }
288     if (byte != 0) {
289         return 1;
290     }
291 
292     rc = spapr_vio_dma_write(dev, dev->crq.qladdr + dev->crq.qnext + 8,
293                              &crq[8], 8);
294     if (rc) {
295         return rc;
296     }
297 
298     kvmppc_eieio();
299 
300     rc = spapr_vio_dma_write(dev, dev->crq.qladdr + dev->crq.qnext, crq, 8);
301     if (rc) {
302         return rc;
303     }
304 
305     dev->crq.qnext = (dev->crq.qnext + 16) % dev->crq.qsize;
306 
307     if (dev->signal_state & 1) {
308         qemu_irq_pulse(spapr_vio_qirq(dev));
309     }
310 
311     return 0;
312 }
313 
314 /* "quiesce" handling */
315 
316 static void spapr_vio_quiesce_one(VIOsPAPRDevice *dev)
317 {
318     if (dev->tcet) {
319         device_reset(DEVICE(dev->tcet));
320     }
321     free_crq(dev);
322 }
323 
324 void spapr_vio_set_bypass(VIOsPAPRDevice *dev, bool bypass)
325 {
326     if (!dev->tcet) {
327         return;
328     }
329 
330     memory_region_set_enabled(&dev->mrbypass, bypass);
331     memory_region_set_enabled(spapr_tce_get_iommu(dev->tcet), !bypass);
332 
333     dev->tcet->bypass = bypass;
334 }
335 
336 static void rtas_set_tce_bypass(PowerPCCPU *cpu, sPAPRMachineState *spapr,
337                                 uint32_t token,
338                                 uint32_t nargs, target_ulong args,
339                                 uint32_t nret, target_ulong rets)
340 {
341     VIOsPAPRBus *bus = spapr->vio_bus;
342     VIOsPAPRDevice *dev;
343     uint32_t unit, enable;
344 
345     if (nargs != 2) {
346         rtas_st(rets, 0, RTAS_OUT_PARAM_ERROR);
347         return;
348     }
349     unit = rtas_ld(args, 0);
350     enable = rtas_ld(args, 1);
351     dev = spapr_vio_find_by_reg(bus, unit);
352     if (!dev) {
353         rtas_st(rets, 0, RTAS_OUT_PARAM_ERROR);
354         return;
355     }
356 
357     if (!dev->tcet) {
358         rtas_st(rets, 0, RTAS_OUT_PARAM_ERROR);
359         return;
360     }
361 
362     spapr_vio_set_bypass(dev, !!enable);
363 
364     rtas_st(rets, 0, RTAS_OUT_SUCCESS);
365 }
366 
367 static void rtas_quiesce(PowerPCCPU *cpu, sPAPRMachineState *spapr,
368                          uint32_t token,
369                          uint32_t nargs, target_ulong args,
370                          uint32_t nret, target_ulong rets)
371 {
372     VIOsPAPRBus *bus = spapr->vio_bus;
373     BusChild *kid;
374     VIOsPAPRDevice *dev = NULL;
375 
376     if (nargs != 0) {
377         rtas_st(rets, 0, RTAS_OUT_PARAM_ERROR);
378         return;
379     }
380 
381     QTAILQ_FOREACH(kid, &bus->bus.children, sibling) {
382         dev = (VIOsPAPRDevice *)kid->child;
383         spapr_vio_quiesce_one(dev);
384     }
385 
386     rtas_st(rets, 0, RTAS_OUT_SUCCESS);
387 }
388 
389 static VIOsPAPRDevice *reg_conflict(VIOsPAPRDevice *dev)
390 {
391     VIOsPAPRBus *bus = SPAPR_VIO_BUS(dev->qdev.parent_bus);
392     BusChild *kid;
393     VIOsPAPRDevice *other;
394 
395     /*
396      * Check for a device other than the given one which is already
397      * using the requested address. We have to open code this because
398      * the given dev might already be in the list.
399      */
400     QTAILQ_FOREACH(kid, &bus->bus.children, sibling) {
401         other = VIO_SPAPR_DEVICE(kid->child);
402 
403         if (other != dev && other->reg == dev->reg) {
404             return other;
405         }
406     }
407 
408     return 0;
409 }
410 
411 static void spapr_vio_busdev_reset(DeviceState *qdev)
412 {
413     VIOsPAPRDevice *dev = VIO_SPAPR_DEVICE(qdev);
414     VIOsPAPRDeviceClass *pc = VIO_SPAPR_DEVICE_GET_CLASS(dev);
415 
416     /* Shut down the request queue and TCEs if necessary */
417     spapr_vio_quiesce_one(dev);
418 
419     dev->signal_state = 0;
420 
421     spapr_vio_set_bypass(dev, false);
422     if (pc->reset) {
423         pc->reset(dev);
424     }
425 }
426 
427 static void spapr_vio_busdev_realize(DeviceState *qdev, Error **errp)
428 {
429     sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
430     VIOsPAPRDevice *dev = (VIOsPAPRDevice *)qdev;
431     VIOsPAPRDeviceClass *pc = VIO_SPAPR_DEVICE_GET_CLASS(dev);
432     char *id;
433 
434     if (dev->reg != -1) {
435         /*
436          * Explicitly assigned address, just verify that no-one else
437          * is using it.  other mechanism). We have to open code this
438          * rather than using spapr_vio_find_by_reg() because sdev
439          * itself is already in the list.
440          */
441         VIOsPAPRDevice *other = reg_conflict(dev);
442 
443         if (other) {
444             error_setg(errp, "%s and %s devices conflict at address %#x",
445                        object_get_typename(OBJECT(qdev)),
446                        object_get_typename(OBJECT(&other->qdev)),
447                        dev->reg);
448             return;
449         }
450     } else {
451         /* Need to assign an address */
452         VIOsPAPRBus *bus = SPAPR_VIO_BUS(dev->qdev.parent_bus);
453 
454         do {
455             dev->reg = bus->next_reg++;
456         } while (reg_conflict(dev));
457     }
458 
459     /* Don't overwrite ids assigned on the command line */
460     if (!dev->qdev.id) {
461         id = spapr_vio_get_dev_name(DEVICE(dev));
462         dev->qdev.id = id;
463     }
464 
465     dev->irq = xics_alloc(spapr->icp, 0, dev->irq, false);
466     if (!dev->irq) {
467         error_setg(errp, "can't allocate IRQ");
468         return;
469     }
470 
471     if (pc->rtce_window_size) {
472         uint32_t liobn = SPAPR_VIO_LIOBN(dev->reg);
473 
474         memory_region_init(&dev->mrroot, OBJECT(dev), "iommu-spapr-root",
475                            ram_size);
476         memory_region_init_alias(&dev->mrbypass, OBJECT(dev),
477                                  "iommu-spapr-bypass", get_system_memory(),
478                                  0, ram_size);
479         memory_region_add_subregion_overlap(&dev->mrroot, 0, &dev->mrbypass, 1);
480         address_space_init(&dev->as, &dev->mrroot, qdev->id);
481 
482         dev->tcet = spapr_tce_new_table(qdev, liobn,
483                                         0,
484                                         SPAPR_TCE_PAGE_SHIFT,
485                                         pc->rtce_window_size >>
486                                         SPAPR_TCE_PAGE_SHIFT, false);
487         dev->tcet->vdev = dev;
488         memory_region_add_subregion_overlap(&dev->mrroot, 0,
489                                             spapr_tce_get_iommu(dev->tcet), 2);
490     }
491 
492     pc->realize(dev, errp);
493 }
494 
495 static target_ulong h_vio_signal(PowerPCCPU *cpu, sPAPRMachineState *spapr,
496                                  target_ulong opcode,
497                                  target_ulong *args)
498 {
499     target_ulong reg = args[0];
500     target_ulong mode = args[1];
501     VIOsPAPRDevice *dev = spapr_vio_find_by_reg(spapr->vio_bus, reg);
502     VIOsPAPRDeviceClass *pc;
503 
504     if (!dev) {
505         return H_PARAMETER;
506     }
507 
508     pc = VIO_SPAPR_DEVICE_GET_CLASS(dev);
509 
510     if (mode & ~pc->signal_mask) {
511         return H_PARAMETER;
512     }
513 
514     dev->signal_state = mode;
515 
516     return H_SUCCESS;
517 }
518 
519 VIOsPAPRBus *spapr_vio_bus_init(void)
520 {
521     VIOsPAPRBus *bus;
522     BusState *qbus;
523     DeviceState *dev;
524 
525     /* Create bridge device */
526     dev = qdev_create(NULL, TYPE_SPAPR_VIO_BRIDGE);
527     qdev_init_nofail(dev);
528 
529     /* Create bus on bridge device */
530     qbus = qbus_create(TYPE_SPAPR_VIO_BUS, dev, "spapr-vio");
531     bus = SPAPR_VIO_BUS(qbus);
532     bus->next_reg = 0x71000000;
533 
534     /* hcall-vio */
535     spapr_register_hypercall(H_VIO_SIGNAL, h_vio_signal);
536 
537     /* hcall-crq */
538     spapr_register_hypercall(H_REG_CRQ, h_reg_crq);
539     spapr_register_hypercall(H_FREE_CRQ, h_free_crq);
540     spapr_register_hypercall(H_SEND_CRQ, h_send_crq);
541     spapr_register_hypercall(H_ENABLE_CRQ, h_enable_crq);
542 
543     /* RTAS calls */
544     spapr_rtas_register(RTAS_IBM_SET_TCE_BYPASS, "ibm,set-tce-bypass",
545                         rtas_set_tce_bypass);
546     spapr_rtas_register(RTAS_QUIESCE, "quiesce", rtas_quiesce);
547 
548     return bus;
549 }
550 
551 /* Represents sPAPR hcall VIO devices */
552 
553 static int spapr_vio_bridge_init(SysBusDevice *dev)
554 {
555     /* nothing */
556     return 0;
557 }
558 
559 static void spapr_vio_bridge_class_init(ObjectClass *klass, void *data)
560 {
561     SysBusDeviceClass *k = SYS_BUS_DEVICE_CLASS(klass);
562     DeviceClass *dc = DEVICE_CLASS(klass);
563 
564     dc->fw_name = "vdevice";
565     k->init = spapr_vio_bridge_init;
566 }
567 
568 static const TypeInfo spapr_vio_bridge_info = {
569     .name          = TYPE_SPAPR_VIO_BRIDGE,
570     .parent        = TYPE_SYS_BUS_DEVICE,
571     .class_init    = spapr_vio_bridge_class_init,
572 };
573 
574 const VMStateDescription vmstate_spapr_vio = {
575     .name = "spapr_vio",
576     .version_id = 1,
577     .minimum_version_id = 1,
578     .fields = (VMStateField[]) {
579         /* Sanity check */
580         VMSTATE_UINT32_EQUAL(reg, VIOsPAPRDevice),
581         VMSTATE_UINT32_EQUAL(irq, VIOsPAPRDevice),
582 
583         /* General VIO device state */
584         VMSTATE_UINTTL(signal_state, VIOsPAPRDevice),
585         VMSTATE_UINT64(crq.qladdr, VIOsPAPRDevice),
586         VMSTATE_UINT32(crq.qsize, VIOsPAPRDevice),
587         VMSTATE_UINT32(crq.qnext, VIOsPAPRDevice),
588 
589         VMSTATE_END_OF_LIST()
590     },
591 };
592 
593 static void vio_spapr_device_class_init(ObjectClass *klass, void *data)
594 {
595     DeviceClass *k = DEVICE_CLASS(klass);
596     k->realize = spapr_vio_busdev_realize;
597     k->reset = spapr_vio_busdev_reset;
598     k->bus_type = TYPE_SPAPR_VIO_BUS;
599     k->props = spapr_vio_props;
600 }
601 
602 static const TypeInfo spapr_vio_type_info = {
603     .name = TYPE_VIO_SPAPR_DEVICE,
604     .parent = TYPE_DEVICE,
605     .instance_size = sizeof(VIOsPAPRDevice),
606     .abstract = true,
607     .class_size = sizeof(VIOsPAPRDeviceClass),
608     .class_init = vio_spapr_device_class_init,
609 };
610 
611 static void spapr_vio_register_types(void)
612 {
613     type_register_static(&spapr_vio_bus_info);
614     type_register_static(&spapr_vio_bridge_info);
615     type_register_static(&spapr_vio_type_info);
616 }
617 
618 type_init(spapr_vio_register_types)
619 
620 static int compare_reg(const void *p1, const void *p2)
621 {
622     VIOsPAPRDevice const *dev1, *dev2;
623 
624     dev1 = (VIOsPAPRDevice *)*(DeviceState **)p1;
625     dev2 = (VIOsPAPRDevice *)*(DeviceState **)p2;
626 
627     if (dev1->reg < dev2->reg) {
628         return -1;
629     }
630     if (dev1->reg == dev2->reg) {
631         return 0;
632     }
633 
634     /* dev1->reg > dev2->reg */
635     return 1;
636 }
637 
638 int spapr_populate_vdevice(VIOsPAPRBus *bus, void *fdt)
639 {
640     DeviceState *qdev, **qdevs;
641     BusChild *kid;
642     int i, num, ret = 0;
643 
644     /* Count qdevs on the bus list */
645     num = 0;
646     QTAILQ_FOREACH(kid, &bus->bus.children, sibling) {
647         num++;
648     }
649 
650     /* Copy out into an array of pointers */
651     qdevs = g_malloc(sizeof(qdev) * num);
652     num = 0;
653     QTAILQ_FOREACH(kid, &bus->bus.children, sibling) {
654         qdevs[num++] = kid->child;
655     }
656 
657     /* Sort the array */
658     qsort(qdevs, num, sizeof(qdev), compare_reg);
659 
660     /* Hack alert. Give the devices to libfdt in reverse order, we happen
661      * to know that will mean they are in forward order in the tree. */
662     for (i = num - 1; i >= 0; i--) {
663         VIOsPAPRDevice *dev = (VIOsPAPRDevice *)(qdevs[i]);
664 
665         ret = vio_make_devnode(dev, fdt);
666 
667         if (ret < 0) {
668             goto out;
669         }
670     }
671 
672     ret = 0;
673 out:
674     g_free(qdevs);
675 
676     return ret;
677 }
678 
679 int spapr_populate_chosen_stdout(void *fdt, VIOsPAPRBus *bus)
680 {
681     VIOsPAPRDevice *dev;
682     char *name, *path;
683     int ret, offset;
684 
685     dev = spapr_vty_get_default(bus);
686     if (!dev)
687         return 0;
688 
689     offset = fdt_path_offset(fdt, "/chosen");
690     if (offset < 0) {
691         return offset;
692     }
693 
694     name = spapr_vio_get_dev_name(DEVICE(dev));
695     path = g_strdup_printf("/vdevice/%s", name);
696 
697     ret = fdt_setprop_string(fdt, offset, "linux,stdout-path", path);
698 
699     g_free(name);
700     g_free(path);
701 
702     return ret;
703 }
704