summaryrefslogtreecommitdiffstats
path: root/OvmfPkg/VirtioNetDxe/DriverBinding.c
blob: ac9ac2d7fb395b839f6cedcf3f68086195fad4eb (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
/** @file

  Driver Binding code and its private helpers for the virtio-net driver.

  Copyright (C) 2013, Red Hat, Inc.
  Copyright (c) 2006 - 2014, Intel Corporation. All rights reserved.<BR>

  SPDX-License-Identifier: BSD-2-Clause-Patent

**/

#include <Library/BaseMemoryLib.h>
#include <Library/DevicePathLib.h>
#include <Library/MemoryAllocationLib.h>
#include <Library/UefiBootServicesTableLib.h>

#include "VirtioNet.h"

#define RECEIVE_FILTERS_NO_MCAST  ((UINT32) (      \
          EFI_SIMPLE_NETWORK_RECEIVE_UNICAST     | \
          EFI_SIMPLE_NETWORK_RECEIVE_BROADCAST   | \
          EFI_SIMPLE_NETWORK_RECEIVE_PROMISCUOUS   \
          ))

/*
  Temporarily enable then reset the virtio-net device in order to retrieve
  configuration values needed by Simple Network Protocol and Simple Network
  Mode fields.

  Only VirtioNetSnpPopulate() may call this function.

  If the function fails for any reason, the virtio-net device is moved to
  VSTAT_FAILED instead of being reset. This serves only informative purposes
  for the host side.

  param[in,out] Dev                 The VNET_DEV structure being created for
                                    the virtio-net device.
  param[out] MacAddress             MAC address configured by the host.
  param[out] MediaPresentSupported  Link status is made available by the host.
  param[out] MediaPresent           If link status is made available by the
                                    host, the current link status is stored in
                                    *MediaPresent. Otherwise MediaPresent is
                                    unused.

  @retval EFI_UNSUPPORTED           The host doesn't supply a MAC address.
  @return                           Status codes from VirtIo protocol members.
  @retval EFI_SUCCESS               Configuration values retrieved.
*/
STATIC
EFI_STATUS
EFIAPI
VirtioNetGetFeatures (
  IN OUT  VNET_DEV         *Dev,
  OUT     EFI_MAC_ADDRESS  *MacAddress,
  OUT     BOOLEAN          *MediaPresentSupported,
  OUT     BOOLEAN          *MediaPresent
  )
{
  EFI_STATUS  Status;
  UINT8       NextDevStat;
  UINT64      Features;
  UINTN       MacIdx;
  UINT16      LinkStatus;

  //
  // Interrogate the device for features (virtio-0.9.5, 2.2.1 Device
  // Initialization Sequence), but don't complete setting it up.
  //
  NextDevStat = 0;             // step 1 -- reset device
  Status      = Dev->VirtIo->SetDeviceStatus (Dev->VirtIo, NextDevStat);
  if (EFI_ERROR (Status)) {
    return Status;
  }

  NextDevStat |= VSTAT_ACK;    // step 2 -- acknowledge device presence
  Status       = Dev->VirtIo->SetDeviceStatus (Dev->VirtIo, NextDevStat);
  if (EFI_ERROR (Status)) {
    goto YieldDevice;
  }

  NextDevStat |= VSTAT_DRIVER; // step 3 -- we know how to drive it
  Status       = Dev->VirtIo->SetDeviceStatus (Dev->VirtIo, NextDevStat);
  if (EFI_ERROR (Status)) {
    goto YieldDevice;
  }

  //
  // step 4a -- retrieve and validate features
  //
  Status = Dev->VirtIo->GetDeviceFeatures (Dev->VirtIo, &Features);
  if (EFI_ERROR (Status)) {
    goto YieldDevice;
  }

  //
  // get MAC address byte-wise
  //
  if ((Features & VIRTIO_NET_F_MAC) == 0) {
    Status = EFI_UNSUPPORTED;
    goto YieldDevice;
  }

  for (MacIdx = 0; MacIdx < SIZE_OF_VNET (Mac); ++MacIdx) {
    Status = Dev->VirtIo->ReadDevice (
                            Dev->VirtIo,
                            OFFSET_OF_VNET (Mac) + MacIdx, // Offset
                            1,                             // FieldSize
                            1,                             // BufferSize
                            &MacAddress->Addr[MacIdx]      // Buffer
                            );
    if (EFI_ERROR (Status)) {
      goto YieldDevice;
    }
  }

  //
  // check if link status is reported, and if so, what the link status is
  //
  if ((Features & VIRTIO_NET_F_STATUS) == 0) {
    *MediaPresentSupported = FALSE;
  } else {
    *MediaPresentSupported = TRUE;
    Status                 = VIRTIO_CFG_READ (Dev, LinkStatus, &LinkStatus);
    if (EFI_ERROR (Status)) {
      goto YieldDevice;
    }

    *MediaPresent = (BOOLEAN)((LinkStatus & VIRTIO_NET_S_LINK_UP) != 0);
  }

YieldDevice:
  Dev->VirtIo->SetDeviceStatus (
                 Dev->VirtIo,
                 EFI_ERROR (Status) ? VSTAT_FAILED : 0
                 );

  return Status;
}

/**
  Set up the Simple Network Protocol fields, the Simple Network Mode fields,
  and the Exit Boot Services Event of the virtio-net driver instance.

  This function may only be called by VirtioNetDriverBindingStart().

  @param[in,out] Dev  The VNET_DEV driver instance being created for the
                      virtio-net device.

  @return              Status codes from the CreateEvent() boot service or the
                       VirtioNetGetFeatures() function.
  @retval EFI_SUCCESS  Configuration successful.
*/
STATIC
EFI_STATUS
EFIAPI
VirtioNetSnpPopulate (
  IN OUT VNET_DEV  *Dev
  )
{
  EFI_STATUS  Status;

  //
  // We set up a function here that is asynchronously callable by an
  // external application to check if there are any packets available for
  // reception. The least urgent task priority level we can specify for such a
  // "software interrupt" is TPL_CALLBACK.
  //
  // TPL_CALLBACK is also the maximum TPL an SNP implementation is allowed to
  // run at (see 6.1 Event, Timer, and Task Priority Services in the UEFI
  // Specification 2.3.1+errC).
  //
  // Since we raise our TPL to TPL_CALLBACK in every single function that
  // accesses the device, and the external application also queues its interest
  // for received packets at the same TPL_CALLBACK, in effect the
  // VirtioNetIsPacketAvailable() function will never interrupt any
  // device-accessing driver function, it will be scheduled in isolation.
  //
  // TPL_CALLBACK (which basically this entire driver runs at) is allowed
  // for "[l]ong term operations (such as file system operations and disk
  // I/O)". Because none of our functions block, we'd satisfy an even stronger
  // requirement.
  //
  Status = gBS->CreateEvent (
                  EVT_NOTIFY_WAIT,
                  TPL_CALLBACK,
                  &VirtioNetIsPacketAvailable,
                  Dev,
                  &Dev->Snp.WaitForPacket
                  );
  if (EFI_ERROR (Status)) {
    return Status;
  }

  Dev->Snp.Revision       = EFI_SIMPLE_NETWORK_PROTOCOL_REVISION;
  Dev->Snp.Start          = &VirtioNetStart;
  Dev->Snp.Stop           = &VirtioNetStop;
  Dev->Snp.Initialize     = &VirtioNetInitialize;
  Dev->Snp.Reset          = &VirtioNetReset;
  Dev->Snp.Shutdown       = &VirtioNetShutdown;
  Dev->Snp.ReceiveFilters = &VirtioNetReceiveFilters;
  Dev->Snp.StationAddress = &VirtioNetStationAddress;
  Dev->Snp.Statistics     = &VirtioNetStatistics;
  Dev->Snp.MCastIpToMac   = &VirtioNetMcastIpToMac;
  Dev->Snp.NvData         = &VirtioNetNvData;
  Dev->Snp.GetStatus      = &VirtioNetGetStatus;
  Dev->Snp.Transmit       = &VirtioNetTransmit;
  Dev->Snp.Receive        = &VirtioNetReceive;
  Dev->Snp.Mode           = &Dev->Snm;

  Dev->Snm.State           = EfiSimpleNetworkStopped;
  Dev->Snm.HwAddressSize   = SIZE_OF_VNET (Mac);
  Dev->Snm.MediaHeaderSize = SIZE_OF_VNET (Mac) +       // dst MAC
                             SIZE_OF_VNET (Mac) +       // src MAC
                             2;                         // Ethertype
  Dev->Snm.MaxPacketSize        = 1500;
  Dev->Snm.NvRamSize            = 0;
  Dev->Snm.NvRamAccessSize      = 0;
  Dev->Snm.ReceiveFilterMask    = RECEIVE_FILTERS_NO_MCAST;
  Dev->Snm.ReceiveFilterSetting = RECEIVE_FILTERS_NO_MCAST;
  Dev->Snm.MaxMCastFilterCount  = 0;
  Dev->Snm.MCastFilterCount     = 0;
  Dev->Snm.IfType               = 1;  // ethernet
  Dev->Snm.MacAddressChangeable = FALSE;
  Dev->Snm.MultipleTxSupported  = TRUE;

  ASSERT (SIZE_OF_VNET (Mac) <= sizeof (EFI_MAC_ADDRESS));

  Status = VirtioNetGetFeatures (
             Dev,
             &Dev->Snm.CurrentAddress,
             &Dev->Snm.MediaPresentSupported,
             &Dev->Snm.MediaPresent
             );
  if (EFI_ERROR (Status)) {
    goto CloseWaitForPacket;
  }

  CopyMem (
    &Dev->Snm.PermanentAddress,
    &Dev->Snm.CurrentAddress,
    SIZE_OF_VNET (Mac)
    );
  SetMem (&Dev->Snm.BroadcastAddress, SIZE_OF_VNET (Mac), 0xFF);

  //
  // VirtioNetExitBoot() is queued by ExitBootServices(); its purpose is to
  // cancel any pending virtio requests. The TPL_CALLBACK reasoning is
  // identical to the one above. There's one difference: this kind of
  // event is "globally visible", which means it can be signalled as soon as
  // we create it. We haven't raised our TPL here, hence VirtioNetExitBoot()
  // could be entered immediately. VirtioNetExitBoot() checks Dev->Snm.State,
  // so we're safe.
  //
  Status = gBS->CreateEvent (
                  EVT_SIGNAL_EXIT_BOOT_SERVICES,
                  TPL_CALLBACK,
                  &VirtioNetExitBoot,
                  Dev,
                  &Dev->ExitBoot
                  );
  if (EFI_ERROR (Status)) {
    goto CloseWaitForPacket;
  }

  return EFI_SUCCESS;

CloseWaitForPacket:
  gBS->CloseEvent (Dev->Snp.WaitForPacket);
  return Status;
}

/**
  Release any resources allocated by VirtioNetSnpPopulate().

  This function may only be called by VirtioNetDriverBindingStart(), when
  rolling back a partial, failed driver instance creation, and by
  VirtioNetDriverBindingStop(), when disconnecting a virtio-net device from the
  driver.

  @param[in,out] Dev  The VNET_DEV driver instance being destroyed.
*/
STATIC
VOID
EFIAPI
VirtioNetSnpEvacuate (
  IN OUT VNET_DEV  *Dev
  )
{
  //
  // This function runs either at TPL_CALLBACK already (from
  // VirtioNetDriverBindingStop()), or it is part of a teardown following
  // a partial, failed construction in VirtioNetDriverBindingStart(), when
  // WaitForPacket was never accessible to the world.
  //
  gBS->CloseEvent (Dev->ExitBoot);
  gBS->CloseEvent (Dev->Snp.WaitForPacket);
}

/**
  Tests to see if this driver supports a given controller. If a child device is
  provided, it further tests to see if this driver supports creating a handle
  for the specified child device.

  This function checks to see if the driver specified by This supports the
  device specified by ControllerHandle. Drivers will typically use the device
  path attached to ControllerHandle and/or the services from the bus I/O
  abstraction attached to ControllerHandle to determine if the driver supports
  ControllerHandle. This function may be called many times during platform
  initialization. In order to reduce boot times, the tests performed by this
  function must be very small, and take as little time as possible to execute.
  This function must not change the state of any hardware devices, and this
  function must be aware that the device specified by ControllerHandle may
  already be managed by the same driver or a different driver. This function
  must match its calls to AllocatePages() with FreePages(), AllocatePool() with
  FreePool(), and OpenProtocol() with CloseProtocol(). Because ControllerHandle
  may have been previously started by the same driver, if a protocol is already
  in the opened state, then it must not be closed with CloseProtocol(). This is
  required to guarantee the state of ControllerHandle is not modified by this
  function.

  @param[in]  This                 A pointer to the EFI_DRIVER_BINDING_PROTOCOL
                                   instance.
  @param[in]  ControllerHandle     The handle of the controller to test. This
                                   handle must support a protocol interface
                                   that supplies an I/O abstraction to the
                                   driver.
  @param[in]  RemainingDevicePath  A pointer to the remaining portion of a
                                   device path.  This parameter is ignored by
                                   device drivers, and is optional for bus
                                   drivers. For bus drivers, if this parameter
                                   is not NULL, then the bus driver must
                                   determine if the bus controller specified by
                                   ControllerHandle and the child controller
                                   specified by RemainingDevicePath are both
                                   supported by this bus driver.

  @retval EFI_SUCCESS              The device specified by ControllerHandle and
                                   RemainingDevicePath is supported by the
                                   driver specified by This.
  @retval EFI_ALREADY_STARTED      The device specified by ControllerHandle and
                                   RemainingDevicePath is already being managed
                                   by the driver specified by This.
  @retval EFI_ACCESS_DENIED        The device specified by ControllerHandle and
                                   RemainingDevicePath is already being managed
                                   by a different driver or an application that
                                   requires exclusive access. Currently not
                                   implemented.
  @retval EFI_UNSUPPORTED          The device specified by ControllerHandle and
                                   RemainingDevicePath is not supported by the
                                   driver specified by This.
**/
STATIC
EFI_STATUS
EFIAPI
VirtioNetDriverBindingSupported (
  IN EFI_DRIVER_BINDING_PROTOCOL  *This,
  IN EFI_HANDLE                   DeviceHandle,
  IN EFI_DEVICE_PATH_PROTOCOL     *RemainingDevicePath
  )
{
  EFI_STATUS              Status;
  VIRTIO_DEVICE_PROTOCOL  *VirtIo;

  //
  // Attempt to open the device with the VirtIo set of interfaces. On success,
  // the protocol is "instantiated" for the VirtIo device. Covers duplicate open
  // attempts (EFI_ALREADY_STARTED).
  //
  Status = gBS->OpenProtocol (
                  DeviceHandle,               // candidate device
                  &gVirtioDeviceProtocolGuid, // for generic VirtIo access
                  (VOID **)&VirtIo,           // handle to instantiate
                  This->DriverBindingHandle,  // requestor driver identity
                  DeviceHandle,               // ControllerHandle, according to
                                              // the UEFI Driver Model
                  EFI_OPEN_PROTOCOL_BY_DRIVER // get exclusive VirtIo access to
                                              // the device; to be released
                  );
  if (EFI_ERROR (Status)) {
    return Status;
  }

  if (VirtIo->SubSystemDeviceId != VIRTIO_SUBSYSTEM_NETWORK_CARD) {
    Status = EFI_UNSUPPORTED;
  }

  //
  // We needed VirtIo access only transitorily, to see whether we support the
  // device or not.
  //
  gBS->CloseProtocol (
         DeviceHandle,
         &gVirtioDeviceProtocolGuid,
         This->DriverBindingHandle,
         DeviceHandle
         );
  return Status;
}

/**
  Starts a device controller or a bus controller.

  The Start() function is designed to be invoked from the EFI boot service
  ConnectController(). As a result, much of the error checking on the
  parameters to Start() has been moved into this  common boot service. It is
  legal to call Start() from other locations,  but the following calling
  restrictions must be followed, or the system behavior will not be
  deterministic.
  1. ControllerHandle must be a valid EFI_HANDLE.
  2. If RemainingDevicePath is not NULL, then it must be a pointer to a
     naturally aligned EFI_DEVICE_PATH_PROTOCOL.
  3. Prior to calling Start(), the Supported() function for the driver
     specified by This must have been called with the same calling parameters,
     and Supported() must have returned EFI_SUCCESS.

  @param[in]  This                 A pointer to the EFI_DRIVER_BINDING_PROTOCOL
                                   instance.
  @param[in]  ControllerHandle     The handle of the controller to start. This
                                   handle  must support a protocol interface
                                   that supplies  an I/O abstraction to the
                                   driver.
  @param[in]  RemainingDevicePath  A pointer to the remaining portion of a
                                   device path.  This  parameter is ignored by
                                   device drivers, and is optional for bus
                                   drivers. For a bus driver, if this parameter
                                   is NULL, then handles  for all the children
                                   of Controller are created by this driver.
                                   If this parameter is not NULL and the first
                                   Device Path Node is  not the End of Device
                                   Path Node, then only the handle for the
                                   child device specified by the first Device
                                   Path Node of  RemainingDevicePath is created
                                   by this driver. If the first Device Path
                                   Node of RemainingDevicePath is  the End of
                                   Device Path Node, no child handle is created
                                   by this driver.

  @retval EFI_SUCCESS              The device was started.
  @retval EFI_DEVICE_ERROR         The device could not be started due to a
                                   device error.Currently not implemented.
  @retval EFI_OUT_OF_RESOURCES     The request could not be completed due to a
                                   lack of resources.
  @retval Others                   The driver failed to start the device.

**/
STATIC
EFI_STATUS
EFIAPI
VirtioNetDriverBindingStart (
  IN EFI_DRIVER_BINDING_PROTOCOL  *This,
  IN EFI_HANDLE                   DeviceHandle,
  IN EFI_DEVICE_PATH_PROTOCOL     *RemainingDevicePath
  )
{
  EFI_STATUS                Status;
  VNET_DEV                  *Dev;
  EFI_DEVICE_PATH_PROTOCOL  *DevicePath;
  MAC_ADDR_DEVICE_PATH      MacNode;
  VOID                      *ChildVirtIo;

  //
  // allocate space for the driver instance
  //
  Dev = (VNET_DEV *)AllocateZeroPool (sizeof *Dev);
  if (Dev == NULL) {
    return EFI_OUT_OF_RESOURCES;
  }

  Dev->Signature = VNET_SIG;

  Status = gBS->OpenProtocol (
                  DeviceHandle,
                  &gVirtioDeviceProtocolGuid,
                  (VOID **)&Dev->VirtIo,
                  This->DriverBindingHandle,
                  DeviceHandle,
                  EFI_OPEN_PROTOCOL_BY_DRIVER
                  );
  if (EFI_ERROR (Status)) {
    goto FreeVirtioNet;
  }

  //
  // now we can run a basic one-shot virtio-net initialization required to
  // retrieve the MAC address
  //
  Status = VirtioNetSnpPopulate (Dev);
  if (EFI_ERROR (Status)) {
    goto CloseVirtIo;
  }

  //
  // get the device path of the virtio-net device -- one-shot open
  //
  Status = gBS->OpenProtocol (
                  DeviceHandle,
                  &gEfiDevicePathProtocolGuid,
                  (VOID **)&DevicePath,
                  This->DriverBindingHandle,
                  DeviceHandle,
                  EFI_OPEN_PROTOCOL_GET_PROTOCOL
                  );
  if (EFI_ERROR (Status)) {
    goto Evacuate;
  }

  //
  // create another device path that has the MAC address appended
  //
  MacNode.Header.Type    = MESSAGING_DEVICE_PATH;
  MacNode.Header.SubType = MSG_MAC_ADDR_DP;
  SetDevicePathNodeLength (&MacNode, sizeof MacNode);
  CopyMem (
    &MacNode.MacAddress,
    &Dev->Snm.CurrentAddress,
    sizeof (EFI_MAC_ADDRESS)
    );
  MacNode.IfType = Dev->Snm.IfType;

  Dev->MacDevicePath = AppendDevicePathNode (DevicePath, &MacNode.Header);
  if (Dev->MacDevicePath == NULL) {
    Status = EFI_OUT_OF_RESOURCES;
    goto Evacuate;
  }

  //
  // create a child handle with the Simple Network Protocol and the new
  // device path installed on it
  //
  Status = gBS->InstallMultipleProtocolInterfaces (
                  &Dev->MacHandle,
                  &gEfiSimpleNetworkProtocolGuid,
                  &Dev->Snp,
                  &gEfiDevicePathProtocolGuid,
                  Dev->MacDevicePath,
                  NULL
                  );
  if (EFI_ERROR (Status)) {
    goto FreeMacDevicePath;
  }

  //
  // make a note that we keep this device open with VirtIo for the sake of this
  // child
  //
  Status = gBS->OpenProtocol (
                  DeviceHandle,
                  &gVirtioDeviceProtocolGuid,
                  &ChildVirtIo,
                  This->DriverBindingHandle,
                  Dev->MacHandle,
                  EFI_OPEN_PROTOCOL_BY_CHILD_CONTROLLER
                  );
  if (EFI_ERROR (Status)) {
    goto UninstallMultiple;
  }

  return EFI_SUCCESS;

UninstallMultiple:
  gBS->UninstallMultipleProtocolInterfaces (
         Dev->MacHandle,
         &gEfiDevicePathProtocolGuid,
         Dev->MacDevicePath,
         &gEfiSimpleNetworkProtocolGuid,
         &Dev->Snp,
         NULL
         );

FreeMacDevicePath:
  FreePool (Dev->MacDevicePath);

Evacuate:
  VirtioNetSnpEvacuate (Dev);

CloseVirtIo:
  gBS->CloseProtocol (
         DeviceHandle,
         &gVirtioDeviceProtocolGuid,
         This->DriverBindingHandle,
         DeviceHandle
         );

FreeVirtioNet:
  FreePool (Dev);

  return Status;
}

/**
  Stops a device controller or a bus controller.

  The Stop() function is designed to be invoked from the EFI boot service
  DisconnectController().  As a result, much of the error checking on the
  parameters to Stop() has been moved  into this common boot service. It is
  legal to call Stop() from other locations,  but the following calling
  restrictions must be followed, or the system behavior will not be
  deterministic.
  1. ControllerHandle must be a valid EFI_HANDLE that was used on a previous
     call to this same driver's Start() function.
  2. The first NumberOfChildren handles of ChildHandleBuffer must all be a
     valid EFI_HANDLE. In addition, all of these handles must have been created
     in this driver's Start() function, and the Start() function must have
     called OpenProtocol() on ControllerHandle with an Attribute of
     EFI_OPEN_PROTOCOL_BY_CHILD_CONTROLLER.

  @param[in]  This              A pointer to the EFI_DRIVER_BINDING_PROTOCOL
                                instance.
  @param[in]  ControllerHandle  A handle to the device being stopped. The
                                handle must  support a bus specific I/O
                                protocol for the driver  to use to stop the
                                device.
  @param[in]  NumberOfChildren  The number of child device handles in
                                ChildHandleBuffer.
  @param[in]  ChildHandleBuffer An array of child handles to be freed. May be
                                NULL  if NumberOfChildren is 0.

  @retval EFI_SUCCESS           The device was stopped.
  @retval EFI_DEVICE_ERROR      The device could not be stopped due to a device
                                error.

**/
STATIC
EFI_STATUS
EFIAPI
VirtioNetDriverBindingStop (
  IN EFI_DRIVER_BINDING_PROTOCOL  *This,
  IN EFI_HANDLE                   DeviceHandle,
  IN UINTN                        NumberOfChildren,
  IN EFI_HANDLE                   *ChildHandleBuffer
  )
{
  if (NumberOfChildren > 0) {
    //
    // free all resources for whose access we need the child handle, because
    // the child handle is going away
    //
    EFI_STATUS                   Status;
    EFI_SIMPLE_NETWORK_PROTOCOL  *Snp;
    VNET_DEV                     *Dev;
    EFI_TPL                      OldTpl;

    ASSERT (NumberOfChildren == 1);

    Status = gBS->OpenProtocol (
                    ChildHandleBuffer[0],
                    &gEfiSimpleNetworkProtocolGuid,
                    (VOID **)&Snp,
                    This->DriverBindingHandle,
                    DeviceHandle,
                    EFI_OPEN_PROTOCOL_GET_PROTOCOL
                    );
    ASSERT_EFI_ERROR (Status);
    Dev = VIRTIO_NET_FROM_SNP (Snp);

    //
    // prevent any interference with WaitForPacket
    //
    OldTpl = gBS->RaiseTPL (TPL_CALLBACK);

    ASSERT (Dev->MacHandle == ChildHandleBuffer[0]);
    if (Dev->Snm.State != EfiSimpleNetworkStopped) {
      //
      // device in use, cannot stop driver instance
      //
      Status = EFI_DEVICE_ERROR;
    } else {
      gBS->CloseProtocol (
             DeviceHandle,
             &gVirtioDeviceProtocolGuid,
             This->DriverBindingHandle,
             Dev->MacHandle
             );
      gBS->UninstallMultipleProtocolInterfaces (
             Dev->MacHandle,
             &gEfiDevicePathProtocolGuid,
             Dev->MacDevicePath,
             &gEfiSimpleNetworkProtocolGuid,
             &Dev->Snp,
             NULL
             );
      FreePool (Dev->MacDevicePath);
      VirtioNetSnpEvacuate (Dev);
      FreePool (Dev);
    }

    gBS->RestoreTPL (OldTpl);
    return Status;
  }

  //
  // release remaining resources, tied directly to the parent handle
  //
  gBS->CloseProtocol (
         DeviceHandle,
         &gVirtioDeviceProtocolGuid,
         This->DriverBindingHandle,
         DeviceHandle
         );

  return EFI_SUCCESS;
}

EFI_DRIVER_BINDING_PROTOCOL  gVirtioNetDriverBinding = {
  &VirtioNetDriverBindingSupported,
  &VirtioNetDriverBindingStart,
  &VirtioNetDriverBindingStop,
  0x10,
  NULL,
  NULL
};