[PATCH v2 1/1] NetworkPkg/SnpDxe: Remove ExitBootServices event

["Rabeda, Maciej" <maciej.rabeda@intel.com>]

Patch addresses Bugzilla #1972.
During ExitBootServices stage, drivers should not call any
functions known to use Memory Allocation Services. One of such
functions (as per UEFI spec) is UNDI->Shutdown().

Since UNDI drivers during ExitBootServices phase are expected
to put the adapter to such a state that it will not perform any DMA
operations, there is no need to interface UNDI by SNP driver during
that phase.

Finally, since ExitBootServices event notification function in SNP
only calls UNDI->Shutdown() and Stop() functions, there is no need
to create this event at all. Adding PCD to control creation of event
reacting to ExitBootServices() call so that systems with UNDIs relying
on SNP to call their Shutdown() and Stop() can still work.

Signed-off-by: Maciej Rabeda <maciej.rabeda@intel.com>
Cc: Siyuan Fu <siyuan.fu@intel.com>
Cc: Jiaxin Wu <jiaxin.wu@intel.com>
---

Notes:
    v2:
    - modified commit message
    - added PCD to control ExitBootServices() creation event in SnpDxe

 NetworkPkg/SnpDxe/Snp.c      | 38 +++++++++++---------
 NetworkPkg/NetworkPkg.dec    |  7 ++++
 NetworkPkg/SnpDxe/Snp.h      |  1 +
 NetworkPkg/SnpDxe/SnpDxe.inf |  3 ++
 4 files changed, 32 insertions(+), 17 deletions(-)

diff --git a/NetworkPkg/SnpDxe/Snp.c b/NetworkPkg/SnpDxe/Snp.c
index a23af05078bc..03317ffa26f1 100644
--- a/NetworkPkg/SnpDxe/Snp.c
+++ b/NetworkPkg/SnpDxe/Snp.c
@@ -647,19 +647,21 @@ SimpleNetworkDriverStart (
   PxeShutdown (Snp);
   PxeStop (Snp);
 
-  //
-  // Create EXIT_BOOT_SERIVES Event
-  //
-  Status = gBS->CreateEventEx (
-                  EVT_NOTIFY_SIGNAL,
-                  TPL_NOTIFY,
-                  SnpNotifyExitBootServices,
-                  Snp,
-                  &gEfiEventExitBootServicesGuid,
-                  &Snp->ExitBootServicesEvent
-                  );
-  if (EFI_ERROR (Status)) {
-    goto Error_DeleteSNP;
+  if (FixedPcdGetBool (PcdSnpCreateExitBootServicesEvent)) {
+    //
+    // Create EXIT_BOOT_SERIVES Event
+    //
+    Status = gBS->CreateEventEx (
+                    EVT_NOTIFY_SIGNAL,
+                    TPL_NOTIFY,
+                    SnpNotifyExitBootServices,
+                    Snp,
+                    &gEfiEventExitBootServicesGuid,
+                    &Snp->ExitBootServicesEvent
+                    );
+    if (EFI_ERROR (Status)) {
+      goto Error_DeleteSNP;
+    }
   }
 
   //
@@ -778,10 +780,12 @@ SimpleNetworkDriverStop (
     return Status;
   }
 
-  //
-  // Close EXIT_BOOT_SERIVES Event
-  //
-  gBS->CloseEvent (Snp->ExitBootServicesEvent);
+  if (FixedPcdGetBool (PcdSnpCreateExitBootServicesEvent)) {
+    //
+    // Close EXIT_BOOT_SERIVES Event
+    //
+    gBS->CloseEvent (Snp->ExitBootServicesEvent);
+  }
 
   Status = gBS->CloseProtocol (
                   Controller,
diff --git a/NetworkPkg/NetworkPkg.dec b/NetworkPkg/NetworkPkg.dec
index 944b1d1501c0..66e500cbeaf7 100644
--- a/NetworkPkg/NetworkPkg.dec
+++ b/NetworkPkg/NetworkPkg.dec
@@ -109,6 +109,13 @@
   # @Prompt TFTP block size.
   gEfiNetworkPkgTokenSpaceGuid.PcdTftpBlockSize|0x0|UINT64|0x1000000B
 
+  ## Indicates whether SnpDxe driver will create an event that will be notified
+  # upon gBS->ExitBootServices() call.
+  # TRUE - Event being triggered upon ExitBootServices call will be created
+  # FALSE - Event being triggered upon ExitBootServices call will NOT be created
+  # @Prompt Indicates whether SnpDxe creates event for ExitBootServices() call.
+  gEfiNetworkPkgTokenSpaceGuid.PcdSnpCreateExitBootServicesEvent|TRUE|BOOLEAN|0x1000000C
+
 [PcdsFixedAtBuild, PcdsPatchableInModule, PcdsDynamic, PcdsDynamicEx]
   ## IPv6 DHCP Unique Identifier (DUID) Type configuration (From RFCs 3315 and 6355).
   # 01 = DUID Based on Link-layer Address Plus Time [DUID-LLT]
diff --git a/NetworkPkg/SnpDxe/Snp.h b/NetworkPkg/SnpDxe/Snp.h
index e6b62930397d..4f64c525e357 100644
--- a/NetworkPkg/SnpDxe/Snp.h
+++ b/NetworkPkg/SnpDxe/Snp.h
@@ -26,6 +26,7 @@ SPDX-License-Identifier: BSD-2-Clause-Patent
 #include <Library/UefiLib.h>
 #include <Library/MemoryAllocationLib.h>
 #include <Library/PrintLib.h>
+#include <Library/PcdLib.h>
 
 #include <IndustryStandard/Pci.h>
 #include <IndustryStandard/Acpi.h>
diff --git a/NetworkPkg/SnpDxe/SnpDxe.inf b/NetworkPkg/SnpDxe/SnpDxe.inf
index afeb1526cc10..79ea789c0837 100644
--- a/NetworkPkg/SnpDxe/SnpDxe.inf
+++ b/NetworkPkg/SnpDxe/SnpDxe.inf
@@ -73,5 +73,8 @@
   gEfiNetworkInterfaceIdentifierProtocolGuid_31 ## TO_START
   gEfiPciIoProtocolGuid                         ## TO_START
 
+[Pcd]
+  gEfiNetworkPkgTokenSpaceGuid.PcdSnpCreateExitBootServicesEvent   ## CONSUMES
+
 [UserExtensions.TianoCore."ExtraFiles"]
   SnpDxeExtra.uni
-- 
2.17.0.windows.1

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