NetworkPkg/SnpDxe: Register SnpNotifyExitBootServices at TPL_CALLBACK

REF:https://bugzilla.tianocore.org/show_bug.cgi?id=1562

The current SnpDxe implementation registers its ExitBootServices event
notification function (SnpNotifyExitBootServices ()) at TPL_NOTIFY. This
function calls PxeShutdown() which issues an UNDI  shutdown operation.
Ultimately, this may invoke Shutdown() in EFI_SIMPLE_NETWORK_PROTOCOL.

The UEFI specification 2.8A Table 27 "TPL Restrictions" restricts the
TPL
for Simple Network Protocol to <= TPL_CALLBACK. In addition, it has been
observed in some 3rd party UNDI drivers to cause an issue further down
the call stack if the TPL is higher than TPL_CALLBACK on invocation.

Therefore, this commit changes the TPL of SnpNotifyExitBootServices() to
TPL_CALLBACK.

Cc: Siyuan Fu <siyuan.fu@intel.com>
Cc: Maciej Rabeda <maciej.rabeda@linux.intel.com>
Cc: Jiaxin Wu <jiaxin.wu@intel.com>
Signed-off-by: Michael Kubacki <michael.kubacki@microsoft.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Maciej Rabeda <maciej.rabeda@linux.intel.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/NetworkPkg/SnpDxe/Snp.c b/NetworkPkg/SnpDxe/Snp.c
index 078b27cf5e..fe022e16ea 100644
--- a/NetworkPkg/SnpDxe/Snp.c
+++ b/NetworkPkg/SnpDxe/Snp.c
@@ -2,6 +2,7 @@
   Implementation of driver entry point and driver binding protocol.

 

 Copyright (c) 2004 - 2019, Intel Corporation. All rights reserved.<BR>

+Copyright (c) Microsoft Corporation.<BR>

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

 

 **/

@@ -653,7 +654,7 @@ SimpleNetworkDriverStart (
     //

     Status = gBS->CreateEventEx (

                     EVT_NOTIFY_SIGNAL,

-                    TPL_NOTIFY,

+                    TPL_CALLBACK,

                     SnpNotifyExitBootServices,

                     Snp,

                     &gEfiEventExitBootServicesGuid,