[RFC PATCH 04/11] MdeModulePkg/DxeCore: Avoid caching memory mapped FFS files

["Ard Biesheuvel" <ardb@kernel.org>]

If a firmware volume is memory mapped, it means we can access it
contents directly, and so caching serves little purpose beyond
potentially a minor performance improvement. However, given that most
files are read only a single time, and dispatched from a decompressed
firmware volume in DRAM, we can just avoid the redundant caching here.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 MdeModulePkg/Core/Dxe/FwVol/FwVolRead.c | 22 --------------------
 1 file changed, 22 deletions(-)

diff --git a/MdeModulePkg/Core/Dxe/FwVol/FwVolRead.c b/MdeModulePkg/Core/Dxe/FwVol/FwVolRead.c
index 2ff22c93aad48d7e..69df96685d680868 100644
--- a/MdeModulePkg/Core/Dxe/FwVol/FwVolRead.c
+++ b/MdeModulePkg/Core/Dxe/FwVol/FwVolRead.c
@@ -284,7 +284,6 @@ FvReadFile (
   UINT8                   *SrcPtr;
   EFI_FFS_FILE_HEADER     *FfsHeader;
   UINTN                   InputBufferSize;
-  UINTN                   WholeFileSize;
 
   if (NameGuid == NULL) {
     return EFI_INVALID_PARAMETER;
@@ -316,27 +315,6 @@ FvReadFile (
   // Get a pointer to the header
   //
   FfsHeader = FvDevice->LastKey->FfsHeader;
-  if (FvDevice->IsMemoryMapped) {
-    //
-    // Memory mapped FV has not been cached, so here is to cache by file.
-    //
-    if (!FvDevice->LastKey->FileCached) {
-      //
-      // Cache FFS file to memory buffer.
-      //
-      WholeFileSize = IS_FFS_FILE2 (FfsHeader) ? FFS_FILE2_SIZE (FfsHeader) : FFS_FILE_SIZE (FfsHeader);
-      FfsHeader     = AllocateCopyPool (WholeFileSize, FfsHeader);
-      if (FfsHeader == NULL) {
-        return EFI_OUT_OF_RESOURCES;
-      }
-
-      //
-      // Let FfsHeader in FfsFileEntry point to the cached file buffer.
-      //
-      FvDevice->LastKey->FfsHeader  = FfsHeader;
-      FvDevice->LastKey->FileCached = TRUE;
-    }
-  }
 
   //
   // Remember callers buffer size
-- 
2.39.2