fix: split ftw writes if they span blocks

FTW writes from the variable driver could span block boundaries
as the driver won't divvy up the transaction like it does for FVB
writes.
Add logic to the FtwWrite to split the writes if they span block
boundaries.

Signed-off-by: Girish Mahadevan <gmahadevan@nvidia.com>
Reviewed-by: Jeff Brasen <jbrasen@nvidia.com>

Silicon/NVIDIA/Drivers/FvbDxe/FvbDxe.c

@@ -2,9 +2,8 @@
 
   Fvb Driver
 
-  Copyright (c) 2018-2023, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
   Copyright (c) 2011 - 2014, ARM Ltd. All rights reserved.<BR>
-
+  SPDX-FileCopyrightText: Copyright (c) 2018-2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
   SPDX-License-Identifier: BSD-2-Clause-Patent
 
 **/
@@ -866,13 +865,71 @@ FtwWrite (
   IN VOID                               *Buffer
   )
 {
-  return Private->FvbInstance.Write (
-                                &Private->FvbInstance,
-                                Lba,
-                                Offset,
-                                &Length,
-                                Buffer
-                                );
+  EFI_STATUS  Status;
+  UINTN       BytesRemaining;
+  UINTN       CurOffset;
+  UINT32      BlockSize;
+  UINTN       WriteSize;
+  UINTN       ActualWriteSize;
+  EFI_LBA     CurLba;
+  VOID        *BufferPtr;
+
+  BlockSize = Private->BlockIo->Media->BlockSize;
+
+  if (Offset >= BlockSize) {
+    DEBUG ((DEBUG_ERROR, "%a: Invalid Offset value %u BlockSize %u\n", __FUNCTION__, Offset, BlockSize));
+    return EFI_BAD_BUFFER_SIZE;
+  }
+
+  BytesRemaining = Length;
+  CurOffset      = Offset;
+  CurLba         = Lba;
+  BufferPtr      = Buffer;
+  Status         = EFI_SUCCESS;
+
+  while (BytesRemaining > 0) {
+    /* Ensure Writes don't cross Block boundaries.*/
+    if ((CurOffset + BytesRemaining) > BlockSize) {
+      WriteSize = (BlockSize - CurOffset);
+    } else {
+      WriteSize = BytesRemaining;
+    }
+
+    ActualWriteSize = WriteSize;
+    Status          = Private->FvbInstance.Write (
+                                             &Private->FvbInstance,
+                                             CurLba,
+                                             CurOffset,
+                                             &ActualWriteSize,
+                                             BufferPtr
+                                             );
+    if (EFI_ERROR (Status) || (ActualWriteSize != WriteSize)) {
+      DEBUG ((
+        DEBUG_ERROR,
+        "%a: WriteFailed(%r): LBA %lu Offset %u Actual/Expected:%u/%u\n",
+        __FUNCTION__,
+        Status,
+        CurLba,
+        CurOffset,
+        ActualWriteSize,
+        WriteSize
+        ));
+
+      if (!EFI_ERROR (Status)) {
+        DEBUG ((DEBUG_ERROR, "Setting Return To BAD BUFFER SIZE\n"));
+        Status = EFI_BAD_BUFFER_SIZE;
+      }
+
+      break;
+    }
+
+    CurOffset       = 0;
+    BytesRemaining -= WriteSize;
+    CurLba++;
+    BufferPtr = ((UINT8 *)BufferPtr + WriteSize);
+  }
+
+  return Status;
 }
 
 /**