diff --git a/OvmfPkg/Include/Library/QemuFwCfgLib.h b/OvmfPkg/Include/Library/QemuFwCfgLib.h
index 40a07456c5..3e017d53a9 100644
--- a/OvmfPkg/Include/Library/QemuFwCfgLib.h
+++ b/OvmfPkg/Include/Library/QemuFwCfgLib.h
@@ -23,6 +23,13 @@
 //
 #define QEMU_FW_CFG_FNAME_SIZE 56
 
+//
+// If the following bit is set in the UINT32 fw_cfg revision / feature bitmap
+// -- read from key 0x0001 with the basic IO Port or MMIO method --, then the
+// DMA interface is available.
+//
+#define FW_CFG_F_DMA BIT1
+
 //
 // Macros for the FW_CFG_DMA_ACCESS.Control bitmap (in native encoding).
 //
@@ -30,6 +37,7 @@
 #define FW_CFG_DMA_CTL_READ   BIT1
 #define FW_CFG_DMA_CTL_SKIP   BIT2
 #define FW_CFG_DMA_CTL_SELECT BIT3
+#define FW_CFG_DMA_CTL_WRITE  BIT4
 
 typedef enum {
   QemuFwCfgItemSignature            = 0x0000,