[PATCH] MdeModulePkg: allow PlatformBootManagerLib to use BootNext

["Jeshua Smith" <jeshuas@nvidia.com>]

Currently BdsEntry caches BootNext before calling PlatformBootManagerLib
APIs, with the result that:
- If BootNext is already set, a BootNext value written by the APIs will
be ignored and deleted, and the current boot will use the cached
BootNext value.
- If BootNext is not present, a BootNext value written by the APIs will
have no effect on the current boot, but will be used by the next boot.

This patch adds PcdAllowBootNextFromPlatformBootManagerLib so that a
platform can enable PlatformBootManagerLib API calls to set BootNext
to control the current boot.
- If the PCD is FALSE (default), there is no change.
- If the PCD is TRUE, then a BootNext value written by the
PlatformBootManagerLib APIs will affect the current boot.

Signed-off-by: Jeshua Smith <jeshuas@nvidia.com>
---
 MdeModulePkg/MdeModulePkg.dec            |  7 +++++
 MdeModulePkg/Universal/BdsDxe/BdsDxe.inf | 27 ++++++++++---------
 MdeModulePkg/Universal/BdsDxe/BdsEntry.c | 34 ++++++++++++++++++------
 3 files changed, 47 insertions(+), 21 deletions(-)

diff --git a/MdeModulePkg/MdeModulePkg.dec b/MdeModulePkg/MdeModulePkg.dec
index 9605c617b7..0e74131712 100644
--- a/MdeModulePkg/MdeModulePkg.dec
+++ b/MdeModulePkg/MdeModulePkg.dec
@@ -1093,6 +1093,13 @@
   # @Prompt Enable UEFI Stack Guard.
   gEfiMdeModulePkgTokenSpaceGuid.PcdCpuStackGuard|FALSE|BOOLEAN|0x30001055
 
+  ## Indicates whether PlatformBootManagerLib code can set BootNext for the current boot.
+  #  If enabled, setting BootNext in PlatformBootManagerLib controls the current boot.<BR><BR>
+  #   TRUE  - BootNext value from PlatformBootManagerLib will affect the current boot.<BR>
+  #   FALSE - BootNext value from PlatformBootManagerLib will affect the subsequent boot (or be ignored if already set).<BR>
+  # @Prompt Allow PlatformBootManagerLib to set BootNext for the current boot.
+  gEfiMdeModulePkgTokenSpaceGuid.PcdAllowBootNextFromPlatformBootManagerLib|FALSE|BOOLEAN|0x30001056
+
 [PcdsFixedAtBuild, PcdsPatchableInModule]
   ## Dynamic type PCD can be registered callback function for Pcd setting action.
   #  PcdMaxPeiPcdCallBackNumberPerPcdEntry indicates the maximum number of callback function
diff --git a/MdeModulePkg/Universal/BdsDxe/BdsDxe.inf b/MdeModulePkg/Universal/BdsDxe/BdsDxe.inf
index 5bac635def..b7a3560f5f 100644
--- a/MdeModulePkg/Universal/BdsDxe/BdsDxe.inf
+++ b/MdeModulePkg/Universal/BdsDxe/BdsDxe.inf
@@ -85,19 +85,20 @@
   gEfiMdePkgTokenSpaceGuid.PcdUefiVariableDefaultLangDeprecate    ## CONSUMES
 
 [Pcd]
-  gEfiMdePkgTokenSpaceGuid.PcdUefiVariableDefaultLangCodes            ## CONSUMES
-  gEfiMdePkgTokenSpaceGuid.PcdUefiVariableDefaultLang                 ## SOMETIMES_CONSUMES
-  gEfiMdePkgTokenSpaceGuid.PcdUefiVariableDefaultPlatformLangCodes    ## CONSUMES
-  gEfiMdePkgTokenSpaceGuid.PcdUefiVariableDefaultPlatformLang         ## CONSUMES
-  gEfiMdePkgTokenSpaceGuid.PcdHardwareErrorRecordLevel                ## CONSUMES
-  gEfiMdePkgTokenSpaceGuid.PcdPlatformBootTimeOut                     ## CONSUMES
-  gEfiMdeModulePkgTokenSpaceGuid.PcdFirmwareVendor                    ## CONSUMES
-  gEfiMdeModulePkgTokenSpaceGuid.PcdFirmwareRevision                  ## CONSUMES
-  gEfiMdeModulePkgTokenSpaceGuid.PcdConInConnectOnDemand              ## CONSUMES
-  gEfiMdeModulePkgTokenSpaceGuid.PcdErrorCodeSetVariable              ## SOMETIMES_CONSUMES
-  gEfiMdeModulePkgTokenSpaceGuid.PcdTestKeyUsed                       ## CONSUMES
-  gEfiMdeModulePkgTokenSpaceGuid.PcdCapsuleOnDiskSupport              ## CONSUMES
-  gEfiMdeModulePkgTokenSpaceGuid.PcdPlatformRecoverySupport           ## CONSUMES
+  gEfiMdePkgTokenSpaceGuid.PcdUefiVariableDefaultLangCodes                  ## CONSUMES
+  gEfiMdePkgTokenSpaceGuid.PcdUefiVariableDefaultLang                       ## SOMETIMES_CONSUMES
+  gEfiMdePkgTokenSpaceGuid.PcdUefiVariableDefaultPlatformLangCodes          ## CONSUMES
+  gEfiMdePkgTokenSpaceGuid.PcdUefiVariableDefaultPlatformLang               ## CONSUMES
+  gEfiMdePkgTokenSpaceGuid.PcdHardwareErrorRecordLevel                      ## CONSUMES
+  gEfiMdePkgTokenSpaceGuid.PcdPlatformBootTimeOut                           ## CONSUMES
+  gEfiMdeModulePkgTokenSpaceGuid.PcdFirmwareVendor                          ## CONSUMES
+  gEfiMdeModulePkgTokenSpaceGuid.PcdFirmwareRevision                        ## CONSUMES
+  gEfiMdeModulePkgTokenSpaceGuid.PcdConInConnectOnDemand                    ## CONSUMES
+  gEfiMdeModulePkgTokenSpaceGuid.PcdErrorCodeSetVariable                    ## SOMETIMES_CONSUMES
+  gEfiMdeModulePkgTokenSpaceGuid.PcdTestKeyUsed                             ## CONSUMES
+  gEfiMdeModulePkgTokenSpaceGuid.PcdCapsuleOnDiskSupport                    ## CONSUMES
+  gEfiMdeModulePkgTokenSpaceGuid.PcdPlatformRecoverySupport                 ## CONSUMES
+  gEfiMdeModulePkgTokenSpaceGuid.PcdAllowBootNextFromPlatformBootManagerLib ## CONSUMES
 
 [Depex]
   TRUE
diff --git a/MdeModulePkg/Universal/BdsDxe/BdsEntry.c b/MdeModulePkg/Universal/BdsDxe/BdsEntry.c
index 766dde3aae..6450406cce 100644
--- a/MdeModulePkg/Universal/BdsDxe/BdsEntry.c
+++ b/MdeModulePkg/Universal/BdsDxe/BdsEntry.c
@@ -787,15 +787,19 @@ BdsEntry (
 
   //
   // Cache the "BootNext" NV variable before calling any PlatformBootManagerLib APIs
-  // This could avoid the "BootNext" set by PlatformBootManagerLib be consumed in this boot.
-  //
-  GetEfiGlobalVariable2 (EFI_BOOT_NEXT_VARIABLE_NAME, (VOID **)&BootNext, &DataSize);
-  if (DataSize != sizeof (UINT16)) {
-    if (BootNext != NULL) {
-      FreePool (BootNext);
-    }
+  // if the Platform isn't allowed to override BootNext.
+  // If "BootNext" was already set, a "BootNext" value set in PlatformBootManagerLib APIs
+  // will be ignored; otherwise it will not take effect until the next boot.
+  //
+  if (!PcdGetBool (PcdAllowBootNextFromPlatformBootManagerLib)) {
+    GetEfiGlobalVariable2 (EFI_BOOT_NEXT_VARIABLE_NAME, (VOID **)&BootNext, &DataSize);
+    if (DataSize != sizeof (UINT16)) {
+      if (BootNext != NULL) {
+        FreePool (BootNext);
+      }
 
-    BootNext = NULL;
+      BootNext = NULL;
+    }
   }
 
   //
@@ -1048,6 +1052,20 @@ BdsEntry (
 
     EfiBootManagerHotkeyBoot ();
 
+    //
+    // If PlatformBootManagerLib APIs are allowed to override BootNext, read it just before use
+    //
+    if (PcdGetBool (PcdAllowBootNextFromPlatformBootManagerLib)) {
+      GetEfiGlobalVariable2 (EFI_BOOT_NEXT_VARIABLE_NAME, (VOID **)&BootNext, &DataSize);
+      if (DataSize != sizeof (UINT16)) {
+        if (BootNext != NULL) {
+          FreePool (BootNext);
+        }
+
+        BootNext = NULL;
+      }
+    }
+
     if (BootNext != NULL) {
       //
       // Delete "BootNext" NV variable before transferring control to it to prevent loops.
-- 
2.17.1