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+tianoc...@kernel.org>
Cc: Jordan Justen <jordan.l.jus...@intel.com>
Cc: Brijesh Singh <brijesh.si...@amd.com>
Cc: Erdem Aktas <erdemak...@google.com>
Cc: James Bottomley <j...@linux.ibm.com>
Cc: Jiewen Yao <jiewen....@intel.com>
Cc: Tom Lendacky <thomas.lenda...@amd.com>
Cc: Gerd Hoffmann <kra...@redhat.com>
Acked-by: Gerd Hoffmann <kra...@redhat.com>
Signed-off-by: Min Xu <min.m...@intel.com>
---
.../QemuFwCfgLib/QemuFwCfgLibInternal.h | 11 +++++++
OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c | 32 +++++++++++++++++++
.../Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf | 2 ++
3 files changed, 45 insertions(+)
diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLibInternal.h
b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLibInternal.h
index 0b77cad1c030..6f7beb6ac1c7 100644
--- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLibInternal.h
+++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLibInternal.h
@@ -59,4 +59,15 @@ InternalQemuFwCfgDmaBytes (
IN UINT32 Control
);
+/**
+ Check if it is Tdx guest
+
+ @retval TRUE It is Tdx guest
+ @retval FALSE It is not Tdx guest
+**/
+BOOLEAN
+QemuFwCfgIsTdxGuest (
+ VOID
+ );
+
#endif
diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c
b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c
index f696fb7cacaa..b8230613dcea 100644
--- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c
+++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c
@@ -14,12 +14,30 @@
#include <Library/DebugLib.h>
#include <Library/QemuFwCfgLib.h>
#include <Library/MemEncryptSevLib.h>
+#include <WorkArea.h>
#include "QemuFwCfgLibInternal.h"
STATIC BOOLEAN mQemuFwCfgSupported = FALSE;
STATIC BOOLEAN mQemuFwCfgDmaSupported;
+/**
+ Check if it is Tdx guest
+
+ @retval TRUE It is Tdx guest
+ @retval FALSE It is not Tdx guest
+**/
+BOOLEAN
+QemuFwCfgIsTdxGuest (
+ VOID
+ )
+{
+ CONFIDENTIAL_COMPUTING_WORK_AREA_HEADER *CcWorkAreaHeader;
+
+ CcWorkAreaHeader = (CONFIDENTIAL_COMPUTING_WORK_AREA_HEADER *)FixedPcdGet32
(PcdOvmfWorkAreaBase);
+ return (CcWorkAreaHeader != NULL && CcWorkAreaHeader->GuestType ==
GUEST_TYPE_INTEL_TDX);
+}
+
/**
Returns a boolean indicating if the firmware configuration interface
is available or not.
@@ -81,6 +99,14 @@ QemuFwCfgInitialize (
//
if (MemEncryptSevIsEnabled ()) {
DEBUG ((DEBUG_INFO, "SEV: QemuFwCfg fallback to IO Port interface.\n"));
+ } else if (QemuFwCfgIsTdxGuest ()) {
+ //
+ // 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"));
@@ -163,6 +189,12 @@ InternalQemuFwCfgDmaBytes (
//
ASSERT (!MemEncryptSevIsEnabled ());
+ //
+ // TDX does not support DMA operations in PEI stage, we should
+ // not have reached here.
+ //
+ ASSERT (!QemuFwCfgIsTdxGuest ());
+
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..3910511880c9 100644
--- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf
+++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf
@@ -43,3 +43,5 @@
MemoryAllocationLib
MemEncryptSevLib
+[Pcd]
+ gUefiOvmfPkgTokenSpaceGuid.PcdOvmfWorkAreaBase
--
2.29.2.windows.2
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