From fb18a9de632e94ed7f62ff225741b82a78bac738 Mon Sep 17 00:00:00 2001
From: Alexander Graf <graf@amazon.com>
Date: Tue, 7 Feb 2023 14:45:45 +0000
Subject: [PATCH] ExtVarStore: Add hook to force enable TRANSFER
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We want to give other modules the ability to switch to TRANSFER mode if
they detect that we are not running in an environment that is compatible
with the shared physical page concept. Let's add a special variable
called "X-Nitro-Force-TRANSFER" that when set toggles the system wide
mode to TRANSFER based.

Upstream-status: Not applicable

Signed-off-by: Alexander Graf <graf@amazon.com>
Reviewed-by: Hendrik Borghorst <hborghor@amazon.de>
Reviewed-by: Johanna 'Mimoja' Amélie Schander <mimoja@amazon.de>

diff --git a/nitro/ExtVarStore/ExtVarStore.c b/nitro/ExtVarStore/ExtVarStore.c
index bcac0eb979..f8924fd765 100644
--- a/nitro/ExtVarStore/ExtVarStore.c
+++ b/nitro/ExtVarStore/ExtVarStore.c
@@ -360,6 +360,17 @@ ExtSetVariable (
   if (VariableName[0] == '\0')
     return EFI_INVALID_PARAMETER;
 
+  /* Magic key to enable TRANSFER based transport */
+  if (StrCmp(VariableName, L"X-Nitro-Force-TRANSFER") == 0) {
+    struct feature_word features = {};
+
+    if ((read_feature_flags(&features) == EFI_SUCCESS) &&
+        (features.features & FEATURE_CRC32) &&
+        (features.features & FEATURE_TRANSFER)) {
+      bounceData = TRUE;
+    }
+  }
+
   uefi_param_buf buf = {
     .buf = comm_buf,
     .remaining = SHMEM_PAGES * EFI_PAGE_SIZE,