OvmfPkg: implement UEFI driver for Virtio RNG devices

This implements a UEFI driver model driver for Virtio devices of type
VIRTIO_SUBSYSTEM_ENTROPY_SOURCE, and exposes them via instances of
the EFI_RNG_PROTOCOL protocol, supporting the EFI_RNG_ALGORITHM_RAW
algorithm only.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>

3 files changed, 744 insertions, 0 deletions

diff --git a/OvmfPkg/VirtioRngDxe/VirtioRng.c b/OvmfPkg/VirtioRngDxe/VirtioRng.c
new file mode 100644
index 0000000000..8eb1aa300b
--- /dev/null
+++ b/OvmfPkg/VirtioRngDxe/VirtioRng.c
@@ -0,0 +1,653 @@
+/** @file

+

+  This driver produces EFI_RNG_PROTOCOL instances for virtio-rng devices.

+

+  The implementation is based on OvmfPkg/VirtioScsiDxe/VirtioScsi.c

+

+  Copyright (C) 2012, Red Hat, Inc.

+  Copyright (c) 2012 - 2014, Intel Corporation. All rights reserved.<BR>

+

+  This driver:

+

+  Copyright (C) 2016, Linaro Ltd.

+

+  This program and the accompanying materials are licensed and made available

+  under the terms and conditions of the BSD License which accompanies this

+  distribution. The full text of the license may be found at

+  http://opensource.org/licenses/bsd-license.php

+

+  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, WITHOUT

+  WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.

+

+**/

+

+#include <Library/BaseMemoryLib.h>

+#include <Library/DebugLib.h>

+#include <Library/MemoryAllocationLib.h>

+#include <Library/UefiBootServicesTableLib.h>

+#include <Library/UefiLib.h>

+#include <Library/VirtioLib.h>

+

+#include "VirtioRng.h"

+

+/**

+  Returns information about the random number generation implementation.

+

+  @param[in]     This                 A pointer to the EFI_RNG_PROTOCOL

+                                      instance.

+  @param[in,out] RNGAlgorithmListSize On input, the size in bytes of

+                                      RNGAlgorithmList.

+                                      On output with a return code of

+                                      EFI_SUCCESS, the size in bytes of the

+                                      data returned in RNGAlgorithmList. On

+                                      output with a return code of

+                                      EFI_BUFFER_TOO_SMALL, the size of

+                                      RNGAlgorithmList required to obtain the

+                                      list.

+  @param[out] RNGAlgorithmList        A caller-allocated memory buffer filled

+                                      by the driver with one EFI_RNG_ALGORITHM

+                                      element for each supported RNG algorithm.

+                                      The list must not change across multiple

+                                      calls to the same driver. The first

+                                      algorithm in the list is the default

+                                      algorithm for the driver.

+

+  @retval EFI_SUCCESS                 The RNG algorithm list was returned

+                                      successfully.

+  @retval EFI_UNSUPPORTED             The services is not supported by this

+                                      driver.

+  @retval EFI_DEVICE_ERROR            The list of algorithms could not be

+                                      retrieved due to a hardware or firmware

+                                      error.

+  @retval EFI_INVALID_PARAMETER       One or more of the parameters are

+                                      incorrect.

+  @retval EFI_BUFFER_TOO_SMALL        The buffer RNGAlgorithmList is too small

+                                      to hold the result.

+

+**/

+STATIC

+EFI_STATUS

+EFIAPI

+VirtioRngGetInfo (

+  IN      EFI_RNG_PROTOCOL        *This,

+  IN OUT  UINTN                   *RNGAlgorithmListSize,

+  OUT     EFI_RNG_ALGORITHM       *RNGAlgorithmList

+  )

+{

+  if (This == NULL || RNGAlgorithmListSize == NULL) {

+    return EFI_INVALID_PARAMETER;

+  }

+

+  if (*RNGAlgorithmListSize < sizeof (EFI_RNG_ALGORITHM)) {

+    *RNGAlgorithmListSize = sizeof (EFI_RNG_ALGORITHM);

+    return EFI_BUFFER_TOO_SMALL;

+  }

+

+  if (RNGAlgorithmList == NULL) {

+    return EFI_INVALID_PARAMETER;

+  }

+

+  *RNGAlgorithmListSize = sizeof (EFI_RNG_ALGORITHM);

+  CopyGuid (RNGAlgorithmList, &gEfiRngAlgorithmRaw);

+

+  return EFI_SUCCESS;

+}

+

+/**

+  Produces and returns an RNG value using either the default or specified RNG

+  algorithm.

+

+  @param[in]  This                    A pointer to the EFI_RNG_PROTOCOL

+                                      instance.

+  @param[in]  RNGAlgorithm            A pointer to the EFI_RNG_ALGORITHM that

+                                      identifies the RNG algorithm to use. May

+                                      be NULL in which case the function will

+                                      use its default RNG algorithm.

+  @param[in]  RNGValueLength          The length in bytes of the memory buffer

+                                      pointed to by RNGValue. The driver shall

+                                      return exactly this numbers of bytes.

+  @param[out] RNGValue                A caller-allocated memory buffer filled

+                                      by the driver with the resulting RNG

+                                      value.

+

+  @retval EFI_SUCCESS                 The RNG value was returned successfully.

+  @retval EFI_UNSUPPORTED             The algorithm specified by RNGAlgorithm

+                                      is not supported by this driver.

+  @retval EFI_DEVICE_ERROR            An RNG value could not be retrieved due

+                                      to a hardware or firmware error.

+  @retval EFI_NOT_READY               There is not enough random data available

+                                      to satisfy the length requested by

+                                      RNGValueLength.

+  @retval EFI_INVALID_PARAMETER       RNGValue is NULL or RNGValueLength is

+                                      zero.

+

+**/

+STATIC

+EFI_STATUS

+EFIAPI

+VirtioRngGetRNG (

+  IN EFI_RNG_PROTOCOL            *This,

+  IN EFI_RNG_ALGORITHM           *RNGAlgorithm, OPTIONAL

+  IN UINTN                       RNGValueLength,

+  OUT UINT8                      *RNGValue

+  )

+{

+  VIRTIO_RNG_DEV            *Dev;

+  DESC_INDICES              Indices;

+  volatile UINT8            *Buffer;

+  UINTN                     Index;

+  UINT32                    Len;

+  UINT32                    BufferSize;

+  EFI_STATUS                Status;

+

+  if (This == NULL || RNGValueLength == 0 || RNGValue == NULL) {

+    return EFI_INVALID_PARAMETER;

+  }

+

+  //

+  // We only support the raw algorithm, so reject requests for anything else

+  //

+  if (RNGAlgorithm != NULL &&

+      !CompareGuid (RNGAlgorithm, &gEfiRngAlgorithmRaw)) {

+    return EFI_UNSUPPORTED;

+  }

+

+  Buffer = (volatile UINT8 *)AllocatePool (RNGValueLength);

+  if (Buffer == NULL) {

+    return EFI_DEVICE_ERROR;

+  }

+

+  Dev = VIRTIO_ENTROPY_SOURCE_FROM_RNG (This);

+

+  //

+  // The Virtio RNG device may return less data than we asked it to, and can

+  // only return MAX_UINT32 bytes per invocation. So loop as long as needed to

+  // get all the entropy we were asked for.

+  //

+  for (Index = 0; Index < RNGValueLength; Index += Len) {

+    BufferSize = (UINT32)MIN (RNGValueLength - Index, (UINTN)MAX_UINT32);

+

+    VirtioPrepare (&Dev->Ring, &Indices);

+    VirtioAppendDesc (&Dev->Ring,

+      (UINTN)Buffer + Index,

+      BufferSize,

+      VRING_DESC_F_WRITE,

+      &Indices);

+

+    if (VirtioFlush (Dev->VirtIo, 0, &Dev->Ring, &Indices, &Len) !=

+        EFI_SUCCESS) {

+      Status = EFI_DEVICE_ERROR;

+      goto FreeBuffer;

+    }

+    ASSERT (Len > 0);

+    ASSERT (Len <= BufferSize);

+  }

+

+  for (Index = 0; Index < RNGValueLength; Index++) {

+    RNGValue[Index] = Buffer[Index];

+  }

+  Status = EFI_SUCCESS;

+

+FreeBuffer:

+  FreePool ((VOID *)Buffer);

+  return Status;

+}

+

+STATIC

+EFI_STATUS

+EFIAPI

+VirtioRngInit (

+  IN OUT VIRTIO_RNG_DEV *Dev

+  )

+{

+  UINT8      NextDevStat;

+  EFI_STATUS Status;

+  UINT16     QueueSize;

+  UINT32     Features;

+

+  //

+  // Execute virtio-0.9.5, 2.2.1 Device Initialization Sequence.

+  //

+  NextDevStat = 0;             // step 1 -- reset device

+  Status = Dev->VirtIo->SetDeviceStatus (Dev->VirtIo, NextDevStat);

+  if (EFI_ERROR (Status)) {

+    goto Failed;

+  }

+

+  NextDevStat |= VSTAT_ACK;    // step 2 -- acknowledge device presence

+  Status = Dev->VirtIo->SetDeviceStatus (Dev->VirtIo, NextDevStat);

+  if (EFI_ERROR (Status)) {

+    goto Failed;

+  }

+

+  NextDevStat |= VSTAT_DRIVER; // step 3 -- we know how to drive it

+  Status = Dev->VirtIo->SetDeviceStatus (Dev->VirtIo, NextDevStat);

+  if (EFI_ERROR (Status)) {

+    goto Failed;

+  }

+

+  //

+  // Set Page Size - MMIO VirtIo Specific

+  //

+  Status = Dev->VirtIo->SetPageSize (Dev->VirtIo, EFI_PAGE_SIZE);

+  if (EFI_ERROR (Status)) {

+    goto Failed;

+  }

+

+  //

+  // step 4a -- retrieve and validate features

+  //

+  Status = Dev->VirtIo->GetDeviceFeatures (Dev->VirtIo, &Features);

+  if (EFI_ERROR (Status)) {

+    goto Failed;

+  }

+

+  //

+  // step 4b -- allocate request virtqueue, just use #0

+  //

+  Status = Dev->VirtIo->SetQueueSel (Dev->VirtIo, 0);

+  if (EFI_ERROR (Status)) {

+    goto Failed;

+  }

+  Status = Dev->VirtIo->GetQueueNumMax (Dev->VirtIo, &QueueSize);

+  if (EFI_ERROR (Status)) {

+    goto Failed;

+  }

+

+  //

+  // VirtioRngGetRNG() uses one descriptor

+  //

+  if (QueueSize < 1) {

+    Status = EFI_UNSUPPORTED;

+    goto Failed;

+  }

+

+  Status = VirtioRingInit (QueueSize, &Dev->Ring);

+  if (EFI_ERROR (Status)) {

+    goto Failed;

+  }

+

+  //

+  // Additional steps for MMIO: align the queue appropriately, and set the

+  // size. If anything fails from here on, we must release the ring resources.

+  //

+  Status = Dev->VirtIo->SetQueueNum (Dev->VirtIo, QueueSize);

+  if (EFI_ERROR (Status)) {

+    goto ReleaseQueue;

+  }

+

+  Status = Dev->VirtIo->SetQueueAlign (Dev->VirtIo, EFI_PAGE_SIZE);

+  if (EFI_ERROR (Status)) {

+    goto ReleaseQueue;

+  }

+

+  //

+  // step 4c -- Report GPFN (guest-physical frame number) of queue.

+  //

+  Status = Dev->VirtIo->SetQueueAddress (Dev->VirtIo,

+      (UINT32) ((UINTN) Dev->Ring.Base >> EFI_PAGE_SHIFT));

+  if (EFI_ERROR (Status)) {

+    goto ReleaseQueue;

+  }

+

+  //

+  // step 5 -- Report understood features and guest-tuneables. None are

+  // currently defined for VirtioRng, and no generic features are needed by

+  // this driver.

+  //

+  Status = Dev->VirtIo->SetGuestFeatures (Dev->VirtIo, 0);

+  if (EFI_ERROR (Status)) {

+    goto ReleaseQueue;

+  }

+

+  //

+  // step 6 -- initialization complete

+  //

+  NextDevStat |= VSTAT_DRIVER_OK;

+  Status = Dev->VirtIo->SetDeviceStatus (Dev->VirtIo, NextDevStat);

+  if (EFI_ERROR (Status)) {

+    goto ReleaseQueue;

+  }

+

+  //

+  // populate the exported interface's attributes

+  //

+  Dev->Rng.GetInfo    = VirtioRngGetInfo;

+  Dev->Rng.GetRNG     = VirtioRngGetRNG;

+

+  return EFI_SUCCESS;

+

+ReleaseQueue:

+  VirtioRingUninit (&Dev->Ring);

+

+Failed:

+  //

+  // Notify the host about our failure to setup: virtio-0.9.5, 2.2.2.1 Device

+  // Status. VirtIo access failure here should not mask the original error.

+  //

+  NextDevStat |= VSTAT_FAILED;

+  Dev->VirtIo->SetDeviceStatus (Dev->VirtIo, NextDevStat);

+

+  return Status; // reached only via Failed above

+}

+

+

+STATIC

+VOID

+EFIAPI

+VirtioRngUninit (

+  IN OUT VIRTIO_RNG_DEV *Dev

+  )

+{

+  //

+  // Reset the virtual device -- see virtio-0.9.5, 2.2.2.1 Device Status. When

+  // VIRTIO_CFG_WRITE() returns, the host will have learned to stay away from

+  // the old comms area.

+  //

+  Dev->VirtIo->SetDeviceStatus (Dev->VirtIo, 0);

+  VirtioRingUninit (&Dev->Ring);

+}

+

+//

+// Event notification function enqueued by ExitBootServices().

+//

+

+STATIC

+VOID

+EFIAPI

+VirtioRngExitBoot (

+  IN  EFI_EVENT Event,

+  IN  VOID      *Context

+  )

+{

+  VIRTIO_RNG_DEV *Dev;

+

+  //

+  // Reset the device. This causes the hypervisor to forget about the virtio

+  // ring.

+  //

+  // We allocated said ring in EfiBootServicesData type memory, and code

+  // executing after ExitBootServices() is permitted to overwrite it.

+  //

+  Dev = Context;

+  Dev->VirtIo->SetDeviceStatus (Dev->VirtIo, 0);

+}

+

+

+//

+// Probe, start and stop functions of this driver, called by the DXE core for

+// specific devices.

+//

+// The following specifications document these interfaces:

+// - Driver Writer's Guide for UEFI 2.3.1 v1.01, 9 Driver Binding Protocol

+// - UEFI Spec 2.3.1 + Errata C, 10.1 EFI Driver Binding Protocol

+//

+// The implementation follows:

+// - Driver Writer's Guide for UEFI 2.3.1 v1.01

+//   - 5.1.3.4 OpenProtocol() and CloseProtocol()

+// - UEFI Spec 2.3.1 + Errata C

+//   -  6.3 Protocol Handler Services

+//

+

+STATIC

+EFI_STATUS

+EFIAPI

+VirtioRngDriverBindingSupported (

+  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_ENTROPY_SOURCE) {

+    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;

+}

+

+STATIC

+EFI_STATUS

+EFIAPI

+VirtioRngDriverBindingStart (

+  IN EFI_DRIVER_BINDING_PROTOCOL *This,

+  IN EFI_HANDLE                  DeviceHandle,

+  IN EFI_DEVICE_PATH_PROTOCOL    *RemainingDevicePath

+  )

+{

+  VIRTIO_RNG_DEV  *Dev;

+  EFI_STATUS Status;

+

+  Dev = (VIRTIO_RNG_DEV *) AllocateZeroPool (sizeof *Dev);

+  if (Dev == NULL) {

+    return EFI_OUT_OF_RESOURCES;

+  }

+

+  Status = gBS->OpenProtocol (DeviceHandle, &gVirtioDeviceProtocolGuid,

+                  (VOID **)&Dev->VirtIo, This->DriverBindingHandle,

+                  DeviceHandle, EFI_OPEN_PROTOCOL_BY_DRIVER);

+  if (EFI_ERROR (Status)) {

+    goto FreeVirtioRng;

+  }

+

+  //

+  // VirtIo access granted, configure virtio-rng device.

+  //

+  Status = VirtioRngInit (Dev);

+  if (EFI_ERROR (Status)) {

+    goto CloseVirtIo;

+  }

+

+  Status = gBS->CreateEvent (EVT_SIGNAL_EXIT_BOOT_SERVICES, TPL_CALLBACK,

+                  &VirtioRngExitBoot, Dev, &Dev->ExitBoot);

+  if (EFI_ERROR (Status)) {

+    goto UninitDev;

+  }

+

+  //

+  // Setup complete, attempt to export the driver instance's EFI_RNG_PROTOCOL

+  // interface.

+  //

+  Dev->Signature = VIRTIO_RNG_SIG;

+  Status = gBS->InstallProtocolInterface (&DeviceHandle,

+                  &gEfiRngProtocolGuid, EFI_NATIVE_INTERFACE,

+                  &Dev->Rng);

+  if (EFI_ERROR (Status)) {

+    goto CloseExitBoot;

+  }

+

+  return EFI_SUCCESS;

+

+CloseExitBoot:

+  gBS->CloseEvent (Dev->ExitBoot);

+

+UninitDev:

+  VirtioRngUninit (Dev);

+

+CloseVirtIo:

+  gBS->CloseProtocol (DeviceHandle, &gVirtioDeviceProtocolGuid,

+         This->DriverBindingHandle, DeviceHandle);

+

+FreeVirtioRng:

+  FreePool (Dev);

+

+  return Status;

+}

+

+

+STATIC

+EFI_STATUS

+EFIAPI

+VirtioRngDriverBindingStop (

+  IN EFI_DRIVER_BINDING_PROTOCOL *This,

+  IN EFI_HANDLE                  DeviceHandle,

+  IN UINTN                       NumberOfChildren,

+  IN EFI_HANDLE                  *ChildHandleBuffer

+  )

+{

+  EFI_STATUS                      Status;

+  EFI_RNG_PROTOCOL                *Rng;

+  VIRTIO_RNG_DEV                  *Dev;

+

+  Status = gBS->OpenProtocol (

+                  DeviceHandle,                     // candidate device

+                  &gEfiRngProtocolGuid,             // retrieve the RNG iface

+                  (VOID **)&Rng,                    // target pointer

+                  This->DriverBindingHandle,        // requestor driver ident.

+                  DeviceHandle,                     // lookup req. for dev.

+                  EFI_OPEN_PROTOCOL_GET_PROTOCOL    // lookup only, no new ref.

+                  );

+  if (EFI_ERROR (Status)) {

+    return Status;

+  }

+

+  Dev = VIRTIO_ENTROPY_SOURCE_FROM_RNG (Rng);

+

+  //

+  // Handle Stop() requests for in-use driver instances gracefully.

+  //

+  Status = gBS->UninstallProtocolInterface (DeviceHandle,

+                  &gEfiRngProtocolGuid, &Dev->Rng);

+  if (EFI_ERROR (Status)) {

+    return Status;

+  }

+

+  gBS->CloseEvent (Dev->ExitBoot);

+

+  VirtioRngUninit (Dev);

+

+  gBS->CloseProtocol (DeviceHandle, &gVirtioDeviceProtocolGuid,

+         This->DriverBindingHandle, DeviceHandle);

+

+  FreePool (Dev);

+

+  return EFI_SUCCESS;

+}

+

+

+//

+// The static object that groups the Supported() (ie. probe), Start() and

+// Stop() functions of the driver together. Refer to UEFI Spec 2.3.1 + Errata

+// C, 10.1 EFI Driver Binding Protocol.

+//

+STATIC EFI_DRIVER_BINDING_PROTOCOL gDriverBinding = {

+  &VirtioRngDriverBindingSupported,

+  &VirtioRngDriverBindingStart,

+  &VirtioRngDriverBindingStop,

+  0x10, // Version, must be in [0x10 .. 0xFFFFFFEF] for IHV-developed drivers

+  NULL, // ImageHandle, to be overwritten by

+        // EfiLibInstallDriverBindingComponentName2() in VirtioRngEntryPoint()

+  NULL  // DriverBindingHandle, ditto

+};

+

+

+//

+// The purpose of the following scaffolding (EFI_COMPONENT_NAME_PROTOCOL and

+// EFI_COMPONENT_NAME2_PROTOCOL implementation) is to format the driver's name

+// in English, for display on standard console devices. This is recommended for

+// UEFI drivers that follow the UEFI Driver Model. Refer to the Driver Writer's

+// Guide for UEFI 2.3.1 v1.01, 11 UEFI Driver and Controller Names.

+//

+

+STATIC

+EFI_UNICODE_STRING_TABLE mDriverNameTable[] = {

+  { "eng;en", L"Virtio Random Number Generator Driver" },

+  { NULL,     NULL                   }

+};

+

+STATIC

+EFI_COMPONENT_NAME_PROTOCOL gComponentName;

+

+STATIC

+EFI_STATUS

+EFIAPI

+VirtioRngGetDriverName (

+  IN  EFI_COMPONENT_NAME_PROTOCOL *This,

+  IN  CHAR8                       *Language,

+  OUT CHAR16                      **DriverName

+  )

+{

+  return LookupUnicodeString2 (

+           Language,

+           This->SupportedLanguages,

+           mDriverNameTable,

+           DriverName,

+           (BOOLEAN)(This == &gComponentName) // Iso639Language

+           );

+}

+

+STATIC

+EFI_STATUS

+EFIAPI

+VirtioRngGetDeviceName (

+  IN  EFI_COMPONENT_NAME_PROTOCOL *This,

+  IN  EFI_HANDLE                  DeviceHandle,

+  IN  EFI_HANDLE                  ChildHandle,

+  IN  CHAR8                       *Language,

+  OUT CHAR16                      **ControllerName

+  )

+{

+  return EFI_UNSUPPORTED;

+}

+

+STATIC

+EFI_COMPONENT_NAME_PROTOCOL gComponentName = {

+  &VirtioRngGetDriverName,

+  &VirtioRngGetDeviceName,

+  "eng" // SupportedLanguages, ISO 639-2 language codes

+};

+

+STATIC

+EFI_COMPONENT_NAME2_PROTOCOL gComponentName2 = {

+  (EFI_COMPONENT_NAME2_GET_DRIVER_NAME)     &VirtioRngGetDriverName,

+  (EFI_COMPONENT_NAME2_GET_CONTROLLER_NAME) &VirtioRngGetDeviceName,

+  "en" // SupportedLanguages, RFC 4646 language codes

+};

+

+

+//

+// Entry point of this driver.

+//

+EFI_STATUS

+EFIAPI

+VirtioRngEntryPoint (

+  IN EFI_HANDLE       ImageHandle,

+  IN EFI_SYSTEM_TABLE *SystemTable

+  )

+{

+  return EfiLibInstallDriverBindingComponentName2 (

+           ImageHandle,

+           SystemTable,

+           &gDriverBinding,

+           ImageHandle,

+           &gComponentName,

+           &gComponentName2

+           );

+}

diff --git a/OvmfPkg/VirtioRngDxe/VirtioRng.h b/OvmfPkg/VirtioRngDxe/VirtioRng.h
new file mode 100644
index 0000000000..844550a00c
--- /dev/null
+++ b/OvmfPkg/VirtioRngDxe/VirtioRng.h
@@ -0,0 +1,46 @@
+/** @file
+
+  Private definitions of the VirtioRng RNG driver
+
+  Copyright (C) 2016, Linaro Ltd.
+
+  This program and the accompanying materials are licensed and made available
+  under the terms and conditions of the BSD License which accompanies this
+  distribution. The full text of the license may be found at
+  http://opensource.org/licenses/bsd-license.php
+
+  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, WITHOUT
+  WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+
+**/
+
+#ifndef _VIRTIO_RNG_DXE_H_
+#define _VIRTIO_RNG_DXE_H_
+
+#include <Protocol/ComponentName.h>
+#include <Protocol/DriverBinding.h>
+#include <Protocol/Rng.h>
+
+#include <IndustryStandard/Virtio.h>
+
+#define VIRTIO_RNG_SIG SIGNATURE_32 ('V', 'R', 'N', 'G')
+
+typedef struct {
+  //
+  // Parts of this structure are initialized / torn down in various functions
+  // at various call depths. The table to the right should make it easier to
+  // track them.
+  //
+  //                        field              init function       init depth
+  //                        ----------------   ------------------  ----------
+  UINT32                    Signature;      // DriverBindingStart   0
+  VIRTIO_DEVICE_PROTOCOL    *VirtIo;        // DriverBindingStart   0
+  EFI_EVENT                 ExitBoot;       // DriverBindingStart   0
+  VRING                     Ring;           // VirtioRingInit       2
+  EFI_RNG_PROTOCOL          Rng;            // VirtioRngInit        1
+} VIRTIO_RNG_DEV;
+
+#define VIRTIO_ENTROPY_SOURCE_FROM_RNG(RngPointer) \
+          CR (RngPointer, VIRTIO_RNG_DEV, Rng, VIRTIO_RNG_SIG)
+
+#endif
diff --git a/OvmfPkg/VirtioRngDxe/VirtioRng.inf b/OvmfPkg/VirtioRngDxe/VirtioRng.inf
new file mode 100644
index 0000000000..471beb37bc
--- /dev/null
+++ b/OvmfPkg/VirtioRngDxe/VirtioRng.inf
@@ -0,0 +1,45 @@
+## @file

+# This driver produces EFI_RNG_PROTOCOL instances for virtio-rng devices.

+#

+# Copyright (C) 2016, Linaro Ltd.

+#

+# This program and the accompanying materials are licensed and made available

+# under the terms and conditions of the BSD License which accompanies this

+# distribution. The full text of the license may be found at

+# http://opensource.org/licenses/bsd-license.php

+#

+# THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, WITHOUT

+# WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.

+#

+##

+

+[Defines]

+  INF_VERSION                    = 0x00010005

+  BASE_NAME                      = VirtioRngDxe

+  FILE_GUID                      = 58E26F0D-CBAC-4BBA-B70F-18221415665A

+  MODULE_TYPE                    = UEFI_DRIVER

+  VERSION_STRING                 = 1.0

+  ENTRY_POINT                    = VirtioRngEntryPoint

+

+[Sources]

+  VirtioRng.c

+

+[Packages]

+  MdePkg/MdePkg.dec

+  OvmfPkg/OvmfPkg.dec

+

+[LibraryClasses]

+  BaseMemoryLib

+  DebugLib

+  MemoryAllocationLib

+  UefiBootServicesTableLib

+  UefiDriverEntryPoint

+  UefiLib

+  VirtioLib

+

+[Protocols]

+  gEfiRngProtocolGuid              ## BY_START

+  gVirtioDeviceProtocolGuid        ## TO_START

+

+[Guids]

+  gEfiRngAlgorithmRaw