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OvmfPkg: Check Tdx in QemuFwCfgPei to avoid DMA operation 

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@kernel.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Signed-off-by: Min Xu <min.m.xu@intel.com>
This commit is contained in:
Min Xu 2021-07-19 09:08:59 +08:00 committed by mergify[bot]
parent 2b80269d98
commit 6b27c11690
3 changed files with 45 additions and 0 deletions
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11
OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLibInternal.h
View File

@ -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

32
OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c
View File

@ -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);

2
OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf
View File

@ -43,3 +43,5 @@
MemoryAllocationLib
MemEncryptSevLib
[Pcd]
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfWorkAreaBase