From 645988d9b339ae7cbb0077b00dca7c5c62f3c3f0 Mon Sep 17 00:00:00 2001
From: Gerd Hoffmann <kraxel@redhat.com>
Date: Fri, 8 Nov 2024 10:24:03 +0100
Subject: [PATCH] OvmfPkg: add PcdEntryPointOverrideDefaultValue

UefiDriverEntryPointFwCfgOverrideLib will use
PcdEntryPointOverrideDefaultValue to decide what to do in case the
fw_cfg file specified via PcdEntryPointOverrideFwCfgVarName is not
present.  Default is "yes".

This allows to disable drivers by default and only enable them when
requested via fw_cfg.

Also log a message with the config option applied and whenever the
default value or a fw_cfg option was used.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 .../UefiDriverEntryPointFwCfgOverrideLib.c        | 15 ++++++++++++++-
 .../UefiDriverEntryPointFwCfgOverrideLib.inf      |  1 +
 OvmfPkg/OvmfPkg.dec                               |  4 ++++
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/OvmfPkg/Library/UefiDriverEntryPointFwCfgOverrideLib/UefiDriverEntryPointFwCfgOverrideLib.c b/OvmfPkg/Library/UefiDriverEntryPointFwCfgOverrideLib/UefiDriverEntryPointFwCfgOverrideLib.c
index debbacb42f..6de3746a20 100644
--- a/OvmfPkg/Library/UefiDriverEntryPointFwCfgOverrideLib/UefiDriverEntryPointFwCfgOverrideLib.c
+++ b/OvmfPkg/Library/UefiDriverEntryPointFwCfgOverrideLib/UefiDriverEntryPointFwCfgOverrideLib.c
@@ -120,7 +120,20 @@ _ModuleEntryPoint (
                 FixedPcdGetPtr (PcdEntryPointOverrideFwCfgVarName),
                 &Enabled
                 );
-  if (!RETURN_ERROR (RetStatus) && !Enabled) {
+
+  if (RETURN_ERROR (RetStatus)) {
+    Enabled = AsciiStrCmp (FixedPcdGetPtr (PcdEntryPointOverrideDefaultValue), "yes") == 0;
+  }
+
+  DEBUG ((
+    DEBUG_INFO,
+    "EntryPointFwCfgOverride: %a = %a (%a)\n",
+    FixedPcdGetPtr (PcdEntryPointOverrideFwCfgVarName),
+    Enabled ? "enabled" : "disabled",
+    RETURN_ERROR (RetStatus) ? "default" : "fw_cfg"
+    ));
+
+  if (!Enabled) {
     //
     // The QEMU fw_cfg variable tells us not to load this image.  So abort.
     //
diff --git a/OvmfPkg/Library/UefiDriverEntryPointFwCfgOverrideLib/UefiDriverEntryPointFwCfgOverrideLib.inf b/OvmfPkg/Library/UefiDriverEntryPointFwCfgOverrideLib/UefiDriverEntryPointFwCfgOverrideLib.inf
index 263e00ceef..19985b8c29 100644
--- a/OvmfPkg/Library/UefiDriverEntryPointFwCfgOverrideLib/UefiDriverEntryPointFwCfgOverrideLib.inf
+++ b/OvmfPkg/Library/UefiDriverEntryPointFwCfgOverrideLib/UefiDriverEntryPointFwCfgOverrideLib.inf
@@ -37,6 +37,7 @@
 
 [FixedPcd]
   gUefiOvmfPkgTokenSpaceGuid.PcdEntryPointOverrideFwCfgVarName
+  gUefiOvmfPkgTokenSpaceGuid.PcdEntryPointOverrideDefaultValue
 
 #
 # For UEFI drivers, these architectural protocols defined in PI 1.0 spec need
diff --git a/OvmfPkg/OvmfPkg.dec b/OvmfPkg/OvmfPkg.dec
index c1c8198061..7e13d313e6 100644
--- a/OvmfPkg/OvmfPkg.dec
+++ b/OvmfPkg/OvmfPkg.dec
@@ -346,6 +346,10 @@
   #  check to decide whether to abort dispatch of the driver it is linked into.
   gUefiOvmfPkgTokenSpaceGuid.PcdEntryPointOverrideFwCfgVarName|""|VOID*|0x68
 
+  ## The default value UefiDriverEntryPointFwCfgOverrideLib will use in case
+  #  the QEMU fw_cfg variable is not present
+  gUefiOvmfPkgTokenSpaceGuid.PcdEntryPointOverrideDefaultValue|"yes"|VOID*|0x76
+
   ## Restrict boot to EFI applications in firmware volumes.
   gUefiOvmfPkgTokenSpaceGuid.PcdBootRestrictToFirmware|FALSE|BOOLEAN|0x6c