From 8a07311710acba244a1b44910324b3b4afd5889a Mon Sep 17 00:00:00 2001
From: Michael Kubacki <michael.kubacki@microsoft.com>
Date: Thu, 11 Sep 2025 15:51:35 -0400
Subject: [PATCH] MdeModulePkg: Add PcdDelayedDispatchMaxEntries

The current fixed value of 8 for `DELAYED_DISPATCH_MAX_ENTRIES` is
not large enough to accommodate platform usage. This change replaces
the macro with a PCD that can be configured by platforms.

In the case the default PCD value is too small, an error message
explaining that the PCD should be updated will be printed followed
by an assert.

Signed-off-by: Michael Kubacki <michael.kubacki@microsoft.com>
---
 MdeModulePkg/Core/Pei/Dispatcher/Dispatcher.c | 14 ++++++++++----
 MdeModulePkg/Core/Pei/PeiMain.inf             |  1 +
 MdeModulePkg/Include/Guid/DelayedDispatch.h   |  9 ++-------
 MdeModulePkg/MdeModulePkg.dec                 |  4 ++++
 4 files changed, 17 insertions(+), 11 deletions(-)

diff --git a/MdeModulePkg/Core/Pei/Dispatcher/Dispatcher.c b/MdeModulePkg/Core/Pei/Dispatcher/Dispatcher.c
index 4073bad82c..f488943c95 100644
--- a/MdeModulePkg/Core/Pei/Dispatcher/Dispatcher.c
+++ b/MdeModulePkg/Core/Pei/Dispatcher/Dispatcher.c
@@ -134,9 +134,15 @@ PeiDelayedDispatchRegister (
   }
 
   // Check for available entry slots
-  ASSERT (DelayedDispatchTable->Count <= DELAYED_DISPATCH_MAX_ENTRIES);
-  if (DelayedDispatchTable->Count == DELAYED_DISPATCH_MAX_ENTRIES) {
-    DEBUG ((DEBUG_ERROR, "%a Too many entries requested\n", __func__));
+  if (DelayedDispatchTable->Count >= PcdGet32 (PcdDelayedDispatchMaxEntries)) {
+    DEBUG ((
+      DEBUG_ERROR,
+      "%a DelayedDispatchTable->Count = %d. PcdDelayedDispatchMaxEntries (%d) is too small.\n",
+      __func__,
+      DelayedDispatchTable->Count,
+      PcdGet32 (PcdDelayedDispatchMaxEntries)
+      ));
+    ASSERT (DelayedDispatchTable->Count < PcdGet32 (PcdDelayedDispatchMaxEntries));
     Status = EFI_OUT_OF_RESOURCES;
     goto Exit;
   }
@@ -1807,7 +1813,7 @@ PeiDispatcher (
     if (GuidHob != NULL) {
       Private->DelayedDispatchTable = (DELAYED_DISPATCH_TABLE *)(GET_GUID_HOB_DATA (GuidHob));
     } else {
-      TableSize                     = sizeof (DELAYED_DISPATCH_TABLE) + ((DELAYED_DISPATCH_MAX_ENTRIES - 1) * sizeof (DELAYED_DISPATCH_ENTRY));
+      TableSize                     = sizeof (DELAYED_DISPATCH_TABLE) + (PcdGet32 (PcdDelayedDispatchMaxEntries) * sizeof (DELAYED_DISPATCH_ENTRY));
       Private->DelayedDispatchTable = BuildGuidHob (&gEfiDelayedDispatchTableGuid, TableSize);
       if (Private->DelayedDispatchTable != NULL) {
         ZeroMem (Private->DelayedDispatchTable, TableSize);
diff --git a/MdeModulePkg/Core/Pei/PeiMain.inf b/MdeModulePkg/Core/Pei/PeiMain.inf
index 4cd58ee3aa..27977ea9c0 100644
--- a/MdeModulePkg/Core/Pei/PeiMain.inf
+++ b/MdeModulePkg/Core/Pei/PeiMain.inf
@@ -121,6 +121,7 @@
   gEfiMdeModulePkgTokenSpaceGuid.PcdMigrateTemporaryRamFirmwareVolumes      ## CONSUMES
   gEfiMdeModulePkgTokenSpaceGuid.PcdDelayedDispatchMaxDelayUs               ## CONSUMES
   gEfiMdeModulePkgTokenSpaceGuid.PcdDelayedDispatchCompletionTimeoutUs      ## CONSUMES
+  gEfiMdeModulePkgTokenSpaceGuid.PcdDelayedDispatchMaxEntries               ## CONSUMES
 
 # [BootMode]
 # S3_RESUME             ## SOMETIMES_CONSUMES
diff --git a/MdeModulePkg/Include/Guid/DelayedDispatch.h b/MdeModulePkg/Include/Guid/DelayedDispatch.h
index 9be5444e36..0adab21757 100644
--- a/MdeModulePkg/Include/Guid/DelayedDispatch.h
+++ b/MdeModulePkg/Include/Guid/DelayedDispatch.h
@@ -1,7 +1,7 @@
 /** @file
   Definition for structure & defines exported by Delayed Dispatch PPI
 
-  Copyright (c), Microsoft Corporation.
+  Copyright (c) Microsoft Corporation.
 
   SPDX-License-Identifier: BSD-2-Clause-Patent
 
@@ -15,11 +15,6 @@
   0x4b733449, 0x8eff, 0x488c, { 0x92, 0x1a, 0x15, 0x4a, 0xda, 0x25, 0x18, 0x07 } \
   }
 
-//
-// Maximal number of Delayed Dispatch entries supported
-//
-#define DELAYED_DISPATCH_MAX_ENTRIES  8
-
 //
 // Internal structure for delayed dispatch entries.
 // Packing the structures here to save space as they will be stored as HOBs.
@@ -37,7 +32,7 @@ typedef struct {
 typedef struct {
   UINT32                    Count;
   UINT32                    DispCount;
-  DELAYED_DISPATCH_ENTRY    Entry[DELAYED_DISPATCH_MAX_ENTRIES];
+  DELAYED_DISPATCH_ENTRY    Entry[];   // Number of entries is based on PcdDelayedDispatchMaxEntries
 } DELAYED_DISPATCH_TABLE;
 
 #pragma pack (pop)
diff --git a/MdeModulePkg/MdeModulePkg.dec b/MdeModulePkg/MdeModulePkg.dec
index 0cb53f0a8a..3067cf762e 100644
--- a/MdeModulePkg/MdeModulePkg.dec
+++ b/MdeModulePkg/MdeModulePkg.dec
@@ -1735,6 +1735,10 @@
   # @Prompt UFS device initial completion timoeout (us), default value is 600ms.
   gEfiMdeModulePkgTokenSpaceGuid.PcdUfsInitialCompletionTimeout|600000|UINT32|0x00000036
 
+  ## Delayed Dispatch Max Entries
+  # @Prompt Maximum number of delayed dispatch entries. Default value is 8.
+  gEfiMdeModulePkgTokenSpaceGuid.PcdDelayedDispatchMaxEntries|8|UINT32|0x00000037
+
 [PcdsPatchableInModule, PcdsDynamic, PcdsDynamicEx]
   ## This PCD defines the Console output row. The default value is 25 according to UEFI spec.
   #  This PCD could be set to 0 then console output would be at max column and max row.