1 files changed, 93 insertions, 0 deletions
diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgSec.c b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgSec.c
index 63cfee9..31bafa9 100644
--- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgSec.c
+++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgSec.c
@@ -13,7 +13,10 @@
 
 #include <Library/BaseLib.h>
 #include <Library/DebugLib.h>
+#include <Library/PcdLib.h>
 #include <Library/QemuFwCfgLib.h>
+#include <PiPei.h>
+#include <WorkArea.h>
 
 #include "QemuFwCfgLibInternal.h"
 
@@ -119,3 +122,93 @@ InternalQemuFwCfgDmaBytes (
   ASSERT (FALSE);
   CpuDeadLoop ();
 }
+
+#ifdef TDX_PEI_LESS_BOOT
+
+/**
+  Check if the Ovmf work area is built as HobList before invoking Hob services.
+
+  @retval    TRUE   Ovmf work area is not NULL and it is built as HobList.
+  @retval    FALSE   Ovmf work area is NULL or it is not built as HobList.
+**/
+BOOLEAN
+InternalQemuFwCfgCheckOvmfWorkArea (
+  VOID
+  )
+{
+  TDX_WORK_AREA  *TdxWorkArea;
+
+  // QemuFwCfgLib might be called in a very early stage
+  // (at that moment HobList may not be set). So an additional check
+  // to the HobList is needed.
+  TdxWorkArea = (TDX_WORK_AREA *)(UINTN)FixedPcdGet32 (PcdOvmfWorkAreaBase);
+  if ((TdxWorkArea == NULL) || (TdxWorkArea->SecTdxWorkArea.HobList == 0)) {
+    return FALSE;
+  } else {
+    return TRUE;
+  }
+}
+
+/**
+  Get the pointer to the QEMU_FW_CFG_WORK_AREA. This data is used as the
+  workarea to record the ongoing fw_cfg item and offset.
+  @retval   QEMU_FW_CFG_WORK_AREA  Pointer to the QEMU_FW_CFG_WORK_AREA
+  @retval   NULL                QEMU_FW_CFG_WORK_AREA doesn't exist
+**/
+QEMU_FW_CFG_WORK_AREA *
+InternalQemuFwCfgCacheGetWorkArea (
+  VOID
+  )
+{
+  EFI_HOB_GUID_TYPE      *GuidHob;
+  EFI_HOB_PLATFORM_INFO  *PlatformHobinfo;
+
+  if (InternalQemuFwCfgCheckOvmfWorkArea () == FALSE) {
+    return NULL;
+  }
+
+  GuidHob = GetFirstGuidHob (&gUefiOvmfPkgPlatformInfoGuid);
+  if (GuidHob == NULL) {
+    return NULL;
+  }
+
+  PlatformHobinfo = (EFI_HOB_PLATFORM_INFO *)(VOID *)GET_GUID_HOB_DATA (GuidHob);
+  return &(PlatformHobinfo->QemuFwCfgWorkArea);
+}
+
+/**
+ OVMF reads configuration data from QEMU via fw_cfg.
+ For Td-Guest VMM is out of TCB and the configuration data is untrusted.
+ From the security perpective the configuration data shall be measured
+ before it is consumed.
+ This function reads the fw_cfg items and cached them. In the meanwhile these
+ fw_cfg items are measured as well. This is to avoid changing the order when
+ reading the fw_cfg process, which depends on multiple factors(depex, order in
+ the Firmware volume).
+  @retval  RETURN_SUCCESS   - Successfully cache with measurement
+  @retval  Others           - As the error code indicates
+ */
+RETURN_STATUS
+EFIAPI
+QemuFwCfgInitCache (
+  IN OUT EFI_HOB_PLATFORM_INFO  *PlatformInfoHob
+  )
+{
+  if (!QemuFwCfgIsAvailable ()) {
+    DEBUG ((DEBUG_ERROR, "%a: Qemu Fw_Cfg is not Available! \n", __func__));
+    return RETURN_UNSUPPORTED;
+  }
+
+  if (InternalQemuFwCfgCheckOvmfWorkArea () == FALSE) {
+    return RETURN_ABORTED;
+  }
+
+  if (EFI_ERROR (InternalQemuFwCfgInitCache (PlatformInfoHob))) {
+    return RETURN_ABORTED;
+  }
+
+  DEBUG ((DEBUG_INFO, "QemuFwCfgInitCache Pass!!!\n"));
+  return RETURN_SUCCESS;
+}
+
+#endif