When the OS takes over the machine, it calls ExitBootServices() in
order to shut down all resident services and event notifications so
that all asynchronous activity is stopped.

At this point, any DMA masters that are still active should be shut
down. This is especially important for network controllers, since
any activity on the network will trigger DMA writes into memory, which
will no longer be reserved for this purpose once the OS takes over.

So register for the ExitBootServices event, and shut down the controller
at this point if it was started before.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
---
 Silicon/Broadcom/Drivers/Net/BcmGenetDxe/BcmGenetDxe.inf |  4 +++
 Silicon/Broadcom/Drivers/Net/BcmGenetDxe/GenetUtil.h     |  1 +
 Silicon/Broadcom/Drivers/Net/BcmGenetDxe/DriverBinding.c | 35 +++++++++++++++++++-
 3 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/Silicon/Broadcom/Drivers/Net/BcmGenetDxe/BcmGenetDxe.inf b/Silicon/Broadcom/Drivers/Net/BcmGenetDxe/BcmGenetDxe.inf
index 248164249c6e..9b3dc5e62ecf 100644
--- a/Silicon/Broadcom/Drivers/Net/BcmGenetDxe/BcmGenetDxe.inf
+++ b/Silicon/Broadcom/Drivers/Net/BcmGenetDxe/BcmGenetDxe.inf
@@ -44,6 +44,7 @@ [LibraryClasses]
   IoLib
   MemoryAllocationLib
   NetLib
+  UefiBootServicesTableLib
   UefiDriverEntryPoint
   UefiLib
 
@@ -52,6 +53,9 @@ [Protocols]
   gEfiDevicePathProtocolGuid                  ## BY_START
   gEfiSimpleNetworkProtocolGuid               ## BY_START
 
+[Guids]
+  gEfiEventExitBootServicesGuid
+
 [FixedPcd]
   gEmbeddedTokenSpaceGuid.PcdDmaDeviceOffset
   gEmbeddedTokenSpaceGuid.PcdDmaDeviceLimit
diff --git a/Silicon/Broadcom/Drivers/Net/BcmGenetDxe/GenetUtil.h b/Silicon/Broadcom/Drivers/Net/BcmGenetDxe/GenetUtil.h
index ddfbc0806c07..c43bdbe1d6da 100644
--- a/Silicon/Broadcom/Drivers/Net/BcmGenetDxe/GenetUtil.h
+++ b/Silicon/Broadcom/Drivers/Net/BcmGenetDxe/GenetUtil.h
@@ -203,6 +203,7 @@ typedef struct {
   EFI_HANDLE                          ControllerHandle;
 
   EFI_LOCK                            Lock;
+  EFI_EVENT                           ExitBootServicesEvent;
 
   EFI_SIMPLE_NETWORK_PROTOCOL         Snp;
   EFI_SIMPLE_NETWORK_MODE             SnpMode;
diff --git a/Silicon/Broadcom/Drivers/Net/BcmGenetDxe/DriverBinding.c b/Silicon/Broadcom/Drivers/Net/BcmGenetDxe/DriverBinding.c
index dacb3ac7d762..00fbfbc109bb 100644
--- a/Silicon/Broadcom/Drivers/Net/BcmGenetDxe/DriverBinding.c
+++ b/Silicon/Broadcom/Drivers/Net/BcmGenetDxe/DriverBinding.c
@@ -74,6 +74,23 @@ GenetDriverBindingSupported (
   return EFI_SUCCESS;
 }
 
+/**
+  Callback function to shut down the network device at ExitBootServices
+
+  @param  Event                   Pointer to this event
+  @param  Context                 Event handler private data
+
+**/
+STATIC
+VOID
+EFIAPI
+GenetNotifyExitBootServices (
+  EFI_EVENT     Event,
+  VOID          *Context
+  )
+{
+  GenetDisableTxRx ((GENET_PRIVATE_DATA *)Context);
+}
 
 /**
   Starts a device controller or a bus controller.
@@ -171,6 +188,17 @@ GenetDriverBindingStart (
   CopyMem (&Genet->SnpMode.CurrentAddress, &Genet->Dev->MacAddress,
     sizeof(EFI_MAC_ADDRESS));
 
+  Status = gBS->CreateEventEx (EVT_NOTIFY_SIGNAL, TPL_CALLBACK,
+                  GenetNotifyExitBootServices, Genet,
+                  &gEfiEventExitBootServicesGuid,
+                  &Genet->ExitBootServicesEvent);
+  if (EFI_ERROR (Status)) {
+    DEBUG ((DEBUG_WARN,
+      "GenetDriverBindingStart: failed to register for ExitBootServices event - %r\n",
+      Status));
+    goto FreeDevice;
+  }
+
   Status = gBS->InstallMultipleProtocolInterfaces (&ControllerHandle,
                   &gEfiSimpleNetworkProtocolGuid,   &Genet->Snp,
                   NULL);
@@ -182,12 +210,14 @@ GenetDriverBindingStart (
                         &gBcmGenetPlatformDeviceProtocolGuid,
                         This->DriverBindingHandle,
                         ControllerHandle);
-    goto FreeDevice;
+    goto FreeEvent;
   }
 
   Genet->ControllerHandle = ControllerHandle;
   return EFI_SUCCESS;
 
+FreeEvent:
+  gBS->CloseEvent (Genet->ExitBootServicesEvent);
 FreeDevice:
   DEBUG ((DEBUG_WARN, "%a: Returning %r\n", __FUNCTION__, Status));
   FreePool (Genet);
@@ -248,6 +278,9 @@ GenetDriverBindingStop (
     return Status;
   }
 
+  Status = gBS->CloseEvent (Genet->ExitBootServicesEvent);
+  ASSERT_EFI_ERROR (Status);
+
   GenetDmaFree (Genet);
 
   Status = gBS->CloseProtocol (ControllerHandle,
--
2.17.1