[edk2-devel] [PATCH 19/23] OvmfPkg: Check Tdx in QemuFwCfgPei to avoid DMA operation

[Min Xu]

RFC： https://bugzilla.tianocore.org/show_bug.cgi?id=3429

If TDX is enabled then we do not support DMA operation in PEI phase.
This is mainly because DMA in TDX guest requires using bounce buffer
(which need to allocate dynamic memory and allocating a PAGE size'd
buffer can be challenge in PEI phase).

Cc: Ard Biesheuvel <ardb+tianocore at kernel.org>
Cc: Jordan Justen <jordan.l.justen at intel.com>
Cc: Brijesh Singh <brijesh.singh at amd.com>
Cc: Erdem Aktas <erdemaktas at google.com>
Cc: James Bottomley <jejb at linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao at intel.com>
Cc: Tom Lendacky <thomas.lendacky at amd.com>
Signed-off-by: Min Xu <min.m.xu at intel.com>
---
 OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c      | 15 +++++++++++++++
 OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf |  1 +
 2 files changed, 16 insertions(+)

diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c
index ecabd88fab66..aae5f2fcb51f 100644
--- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c
+++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c
@@ -14,6 +14,7 @@
 #include <Library/DebugLib.h>
 #include <Library/QemuFwCfgLib.h>
 #include <Library/MemEncryptSevLib.h>
+#include <Library/TdxProbeLib.h>
 
 #include "QemuFwCfgLibInternal.h"
 
@@ -82,6 +83,14 @@ QemuFwCfgInitialize (
     //
     if (MemEncryptSevIsEnabled ()) {
       DEBUG ((DEBUG_INFO, "SEV: QemuFwCfg fallback to IO Port interface.\n"));
+    } else if (TdxIsEnabled ()) {
+      //
+      // If TDX is enabled then we do not support DMA operations in PEI phase.
+      // This is mainly because DMA in TDX guest requires using bounce buffer
+      // (which need to allocate dynamic memory and allocating a PAGE size'd
+      // buffer can be challenge in PEI phase)
+      //
+      DEBUG ((DEBUG_INFO, "TDX: QemuFwCfg fallback to IO Port interface.\n"));
     } else {
       mQemuFwCfgDmaSupported = TRUE;
       DEBUG ((DEBUG_INFO, "QemuFwCfg interface (DMA) is supported.\n"));
@@ -162,6 +171,12 @@ InternalQemuFwCfgDmaBytes (
   //
   ASSERT (!MemEncryptSevIsEnabled ());
 
+  //
+  // TDX does not support DMA operations in PEI stage, we should
+  // not have reached here.
+  //
+  ASSERT (!TdxIsEnabled ());
+
   Access.Control = SwapBytes32 (Control);
   Access.Length  = SwapBytes32 (Size);
   Access.Address = SwapBytes64 ((UINTN)Buffer);
diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf
index 9f9af7d03201..808cb16f75e1 100644
--- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf
+++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf
@@ -42,4 +42,5 @@
   IoLib
   MemoryAllocationLib
   MemEncryptSevLib
+  TdxProbeLib
 
-- 
2.29.2.windows.2



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