diff options
| author | Tom Lendacky <thomas.lendacky@amd.com> | 2020-08-12 15:21:42 -0500 |
|---|---|---|
| committer | mergify[bot] <37929162+mergify[bot]@users.noreply.github.com> | 2020-08-17 02:46:39 +0000 |
| commit | 7b7508ad784d16a5208c8d12dff43aef6df0835b (patch) | |
| tree | e25d203fc610af2ffa0ff51603f02687c0bbda0a /UefiCpuPkg | |
| parent | e88a5b9833d574f09d91b408367a654595badba8 (diff) | |
| download | edk2-7b7508ad784d16a5208c8d12dff43aef6df0835b.tar.gz edk2-7b7508ad784d16a5208c8d12dff43aef6df0835b.tar.bz2 edk2-7b7508ad784d16a5208c8d12dff43aef6df0835b.zip | |
UefiCpuPkg: Allow AP booting under SEV-ES
BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2198
Typically, an AP is booted using the INIT-SIPI-SIPI sequence. This
sequence is intercepted by the hypervisor, which sets the AP's registers
to the values requested by the sequence. At that point, the hypervisor can
start the AP, which will then begin execution at the appropriate location.
Under SEV-ES, AP booting presents some challenges since the hypervisor is
not allowed to alter the AP's register state. In this situation, we have
to distinguish between the AP's first boot and AP's subsequent boots.
First boot:
Once the AP's register state has been defined (which is before the guest
is first booted) it cannot be altered. Should the hypervisor attempt to
alter the register state, the change would be detected by the hardware
and the VMRUN instruction would fail. Given this, the first boot for the
AP is required to begin execution with this initial register state, which
is typically the reset vector. This prevents the BSP from directing the
AP startup location through the INIT-SIPI-SIPI sequence.
To work around this, the firmware will provide a build time reserved area
that can be used as the initial IP value. The hypervisor can extract this
location value by checking for the SEV-ES reset block GUID that must be
located 48-bytes from the end of the firmware. The format of the SEV-ES
reset block area is:
0x00 - 0x01 - SEV-ES Reset IP
0x02 - 0x03 - SEV-ES Reset CS Segment Base[31:16]
0x04 - 0x05 - Size of the SEV-ES reset block
0x06 - 0x15 - SEV-ES Reset Block GUID
(00f771de-1a7e-4fcb-890e-68c77e2fb44e)
The total size is 22 bytes. Any expansion to this block must be done
by adding new values before existing values.
The hypervisor will use the IP and CS values obtained from the SEV-ES
reset block to set as the AP's initial values. The CS Segment Base
represents the upper 16 bits of the CS segment base and must be left
shifted by 16 bits to form the complete CS segment base value.
Before booting the AP for the first time, the BSP must initialize the
SEV-ES reset area. This consists of programming a FAR JMP instruction
to the contents of a memory location that is also located in the SEV-ES
reset area. The BSP must program the IP and CS values for the FAR JMP
based on values drived from the INIT-SIPI-SIPI sequence.
Subsequent boots:
Again, the hypervisor cannot alter the AP register state, so a method is
required to take the AP out of halt state and redirect it to the desired
IP location. If it is determined that the AP is running in an SEV-ES
guest, then instead of calling CpuSleep(), a VMGEXIT is issued with the
AP Reset Hold exit code (0x80000004). The hypervisor will put the AP in
a halt state, waiting for an INIT-SIPI-SIPI sequence. Once the sequence
is recognized, the hypervisor will resume the AP. At this point the AP
must transition from the current 64-bit long mode down to 16-bit real
mode and begin executing at the derived location from the INIT-SIPI-SIPI
sequence.
Another change is around the area of obtaining the (x2)APIC ID during AP
startup. During AP startup, the AP can't take a #VC exception before the
AP has established a stack. However, the AP stack is set by using the
(x2)APIC ID, which is obtained through CPUID instructions. A CPUID
instruction will cause a #VC, so a different method must be used. The
GHCB protocol supports a method to obtain CPUID information from the
hypervisor through the GHCB MSR. This method does not require a stack,
so it is used to obtain the necessary CPUID information to determine the
(x2)APIC ID.
The new 16-bit protected mode GDT entry is used in order to transition
from 64-bit long mode down to 16-bit real mode.
A new assembler routine is created that takes the AP from 64-bit long mode
to 16-bit real mode. This is located under 1MB in memory and transitions
from 64-bit long mode to 32-bit compatibility mode to 16-bit protected
mode and finally 16-bit real mode.
Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Regression-tested-by: Laszlo Ersek <lersek@redhat.com>
Diffstat (limited to 'UefiCpuPkg')
| -rw-r--r-- | UefiCpuPkg/Library/MpInitLib/DxeMpInitLib.inf | 3 | ||||
| -rw-r--r-- | UefiCpuPkg/Library/MpInitLib/DxeMpLib.c | 70 | ||||
| -rw-r--r-- | UefiCpuPkg/Library/MpInitLib/Ia32/MpEqu.inc | 2 | ||||
| -rw-r--r-- | UefiCpuPkg/Library/MpInitLib/Ia32/MpFuncs.nasm | 15 | ||||
| -rw-r--r-- | UefiCpuPkg/Library/MpInitLib/MpLib.c | 336 | ||||
| -rw-r--r-- | UefiCpuPkg/Library/MpInitLib/MpLib.h | 60 | ||||
| -rw-r--r-- | UefiCpuPkg/Library/MpInitLib/PeiMpInitLib.inf | 3 | ||||
| -rw-r--r-- | UefiCpuPkg/Library/MpInitLib/PeiMpLib.c | 19 | ||||
| -rw-r--r-- | UefiCpuPkg/Library/MpInitLib/X64/MpEqu.inc | 4 | ||||
| -rw-r--r-- | UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm | 239 | ||||
| -rw-r--r-- | UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmmFuncsArch.c | 2 |
11 files changed, 738 insertions, 15 deletions
diff --git a/UefiCpuPkg/Library/MpInitLib/DxeMpInitLib.inf b/UefiCpuPkg/Library/MpInitLib/DxeMpInitLib.inf index 5832765956..1771575c69 100644 --- a/UefiCpuPkg/Library/MpInitLib/DxeMpInitLib.inf +++ b/UefiCpuPkg/Library/MpInitLib/DxeMpInitLib.inf @@ -52,6 +52,7 @@ DebugAgentLib
SynchronizationLib
PcdLib
+ VmgExitLib
[Protocols]
gEfiTimerArchProtocolGuid ## SOMETIMES_CONSUMES
@@ -72,4 +73,6 @@ gUefiCpuPkgTokenSpaceGuid.PcdCpuApTargetCstate ## SOMETIMES_CONSUMES
gUefiCpuPkgTokenSpaceGuid.PcdCpuApStatusCheckIntervalInMicroSeconds ## CONSUMES
gUefiCpuPkgTokenSpaceGuid.PcdSevEsIsEnabled ## CONSUMES
+ gUefiCpuPkgTokenSpaceGuid.PcdSevEsWorkAreaBase ## SOMETIMES_CONSUMES
gEfiMdeModulePkgTokenSpaceGuid.PcdCpuStackGuard ## CONSUMES
+ gEfiMdeModulePkgTokenSpaceGuid.PcdGhcbBase ## CONSUMES
diff --git a/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c b/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c index 8ccddf8e9f..9115ff9e3e 100644 --- a/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c +++ b/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c @@ -12,6 +12,8 @@ #include <Library/UefiBootServicesTableLib.h>
#include <Library/DebugAgentLib.h>
#include <Library/DxeServicesTableLib.h>
+#include <Register/Amd/Fam17Msr.h>
+#include <Register/Amd/Ghcb.h>
#include <Protocol/Timer.h>
@@ -145,6 +147,39 @@ GetModeTransitionBuffer ( }
/**
+ Return the address of the SEV-ES AP jump table.
+
+ This buffer is required in order for an SEV-ES guest to transition from
+ UEFI into an OS.
+
+ @return Return SEV-ES AP jump table buffer
+**/
+UINTN
+GetSevEsAPMemory (
+ VOID
+ )
+{
+ EFI_STATUS Status;
+ EFI_PHYSICAL_ADDRESS StartAddress;
+
+ //
+ // Allocate 1 page for AP jump table page
+ //
+ StartAddress = BASE_4GB - 1;
+ Status = gBS->AllocatePages (
+ AllocateMaxAddress,
+ EfiReservedMemoryType,
+ 1,
+ &StartAddress
+ );
+ ASSERT_EFI_ERROR (Status);
+
+ DEBUG ((DEBUG_INFO, "Dxe: SevEsAPMemory = %lx\n", (UINTN) StartAddress));
+
+ return (UINTN) StartAddress;
+}
+
+/**
Checks APs status and updates APs status if needed.
**/
@@ -219,6 +254,38 @@ CheckApsStatus ( }
/**
+ Get Protected mode code segment with 16-bit default addressing
+ from current GDT table.
+
+ @return Protected mode 16-bit code segment value.
+**/
+UINT16
+GetProtectedMode16CS (
+ VOID
+ )
+{
+ IA32_DESCRIPTOR GdtrDesc;
+ IA32_SEGMENT_DESCRIPTOR *GdtEntry;
+ UINTN GdtEntryCount;
+ UINT16 Index;
+
+ Index = (UINT16) -1;
+ AsmReadGdtr (&GdtrDesc);
+ GdtEntryCount = (GdtrDesc.Limit + 1) / sizeof (IA32_SEGMENT_DESCRIPTOR);
+ GdtEntry = (IA32_SEGMENT_DESCRIPTOR *) GdtrDesc.Base;
+ for (Index = 0; Index < GdtEntryCount; Index++) {
+ if (GdtEntry->Bits.L == 0) {
+ if (GdtEntry->Bits.Type > 8 && GdtEntry->Bits.DB == 0) {
+ break;
+ }
+ }
+ GdtEntry++;
+ }
+ ASSERT (Index != GdtEntryCount);
+ return Index * 8;
+}
+
+/**
Get Protected mode code segment from current GDT table.
@return Protected mode code segment value.
@@ -238,7 +305,7 @@ GetProtectedModeCS ( GdtEntry = (IA32_SEGMENT_DESCRIPTOR *) GdtrDesc.Base;
for (Index = 0; Index < GdtEntryCount; Index++) {
if (GdtEntry->Bits.L == 0) {
- if (GdtEntry->Bits.Type > 8 && GdtEntry->Bits.L == 0) {
+ if (GdtEntry->Bits.Type > 8 && GdtEntry->Bits.DB == 1) {
break;
}
}
@@ -300,6 +367,7 @@ MpInitChangeApLoopCallback ( CpuMpData = GetCpuMpData ();
CpuMpData->PmCodeSegment = GetProtectedModeCS ();
+ CpuMpData->Pm16CodeSegment = GetProtectedMode16CS ();
CpuMpData->ApLoopMode = PcdGet8 (PcdCpuApLoopMode);
mNumberToFinish = CpuMpData->CpuCount - 1;
WakeUpAP (CpuMpData, TRUE, 0, RelocateApLoop, NULL, TRUE);
diff --git a/UefiCpuPkg/Library/MpInitLib/Ia32/MpEqu.inc b/UefiCpuPkg/Library/MpInitLib/Ia32/MpEqu.inc index efb1bc2bf7..4f5a7c859a 100644 --- a/UefiCpuPkg/Library/MpInitLib/Ia32/MpEqu.inc +++ b/UefiCpuPkg/Library/MpInitLib/Ia32/MpEqu.inc @@ -19,7 +19,7 @@ CPU_SWITCH_STATE_IDLE equ 0 CPU_SWITCH_STATE_STORED equ 1
CPU_SWITCH_STATE_LOADED equ 2
-LockLocation equ (RendezvousFunnelProcEnd - RendezvousFunnelProcStart)
+LockLocation equ (SwitchToRealProcEnd - RendezvousFunnelProcStart)
StackStartAddressLocation equ LockLocation + 04h
StackSizeLocation equ LockLocation + 08h
ApProcedureLocation equ LockLocation + 0Ch
diff --git a/UefiCpuPkg/Library/MpInitLib/Ia32/MpFuncs.nasm b/UefiCpuPkg/Library/MpInitLib/Ia32/MpFuncs.nasm index b74046b76a..309d53bf3b 100644 --- a/UefiCpuPkg/Library/MpInitLib/Ia32/MpFuncs.nasm +++ b/UefiCpuPkg/Library/MpInitLib/Ia32/MpFuncs.nasm @@ -216,6 +216,16 @@ CProcedureInvoke: RendezvousFunnelProcEnd:
;-------------------------------------------------------------------------------------
+;SwitchToRealProc procedure follows.
+;NOT USED IN 32 BIT MODE.
+;-------------------------------------------------------------------------------------
+global ASM_PFX(SwitchToRealProc)
+ASM_PFX(SwitchToRealProc):
+SwitchToRealProcStart:
+ jmp $ ; Never reach here
+SwitchToRealProcEnd:
+
+;-------------------------------------------------------------------------------------
; AsmRelocateApLoop (MwaitSupport, ApTargetCState, PmCodeSegment, TopOfApStack, CountTofinish);
;-------------------------------------------------------------------------------------
global ASM_PFX(AsmRelocateApLoop)
@@ -263,6 +273,11 @@ ASM_PFX(AsmGetAddressMap): mov dword [ebx + 0Ch], AsmRelocateApLoopStart
mov dword [ebx + 10h], AsmRelocateApLoopEnd - AsmRelocateApLoopStart
mov dword [ebx + 14h], Flat32Start - RendezvousFunnelProcStart
+ mov dword [ebx + 18h], SwitchToRealProcEnd - SwitchToRealProcStart ; SwitchToRealSize
+ mov dword [ebx + 1Ch], SwitchToRealProcStart - RendezvousFunnelProcStart ; SwitchToRealOffset
+ mov dword [ebx + 20h], SwitchToRealProcStart - Flat32Start ; SwitchToRealNoNxOffset
+ mov dword [ebx + 24h], 0 ; SwitchToRealPM16ModeOffset
+ mov dword [ebx + 28h], 0 ; SwitchToRealPM16ModeSize
popad
ret
diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.c b/UefiCpuPkg/Library/MpInitLib/MpLib.c index 2a3fbeef35..90416c81b6 100644 --- a/UefiCpuPkg/Library/MpInitLib/MpLib.c +++ b/UefiCpuPkg/Library/MpInitLib/MpLib.c @@ -9,6 +9,9 @@ **/
#include "MpLib.h"
+#include <Library/VmgExitLib.h>
+#include <Register/Amd/Fam17Msr.h>
+#include <Register/Amd/Ghcb.h>
EFI_GUID mCpuInitMpLibHobGuid = CPU_INIT_MP_LIB_HOB_GUID;
@@ -291,6 +294,14 @@ GetApLoopMode ( //
ApLoopMode = ApInHltLoop;
}
+
+ if (PcdGetBool (PcdSevEsIsEnabled)) {
+ //
+ // For SEV-ES, force AP in Hlt-loop mode in order to use the GHCB
+ // protocol for starting APs
+ //
+ ApLoopMode = ApInHltLoop;
+ }
}
if (ApLoopMode != ApInMwaitLoop) {
@@ -588,6 +599,112 @@ InitializeApData ( }
/**
+ Get Protected mode code segment with 16-bit default addressing
+ from current GDT table.
+
+ @return Protected mode 16-bit code segment value.
+**/
+STATIC
+UINT16
+GetProtectedMode16CS (
+ VOID
+ )
+{
+ IA32_DESCRIPTOR GdtrDesc;
+ IA32_SEGMENT_DESCRIPTOR *GdtEntry;
+ UINTN GdtEntryCount;
+ UINT16 Index;
+
+ Index = (UINT16) -1;
+ AsmReadGdtr (&GdtrDesc);
+ GdtEntryCount = (GdtrDesc.Limit + 1) / sizeof (IA32_SEGMENT_DESCRIPTOR);
+ GdtEntry = (IA32_SEGMENT_DESCRIPTOR *) GdtrDesc.Base;
+ for (Index = 0; Index < GdtEntryCount; Index++) {
+ if (GdtEntry->Bits.L == 0 &&
+ GdtEntry->Bits.DB == 0 &&
+ GdtEntry->Bits.Type > 8) {
+ break;
+ }
+ GdtEntry++;
+ }
+ ASSERT (Index != GdtEntryCount);
+ return Index * 8;
+}
+
+/**
+ Get Protected mode code segment with 32-bit default addressing
+ from current GDT table.
+
+ @return Protected mode 32-bit code segment value.
+**/
+STATIC
+UINT16
+GetProtectedMode32CS (
+ VOID
+ )
+{
+ IA32_DESCRIPTOR GdtrDesc;
+ IA32_SEGMENT_DESCRIPTOR *GdtEntry;
+ UINTN GdtEntryCount;
+ UINT16 Index;
+
+ Index = (UINT16) -1;
+ AsmReadGdtr (&GdtrDesc);
+ GdtEntryCount = (GdtrDesc.Limit + 1) / sizeof (IA32_SEGMENT_DESCRIPTOR);
+ GdtEntry = (IA32_SEGMENT_DESCRIPTOR *) GdtrDesc.Base;
+ for (Index = 0; Index < GdtEntryCount; Index++) {
+ if (GdtEntry->Bits.L == 0 &&
+ GdtEntry->Bits.DB == 1 &&
+ GdtEntry->Bits.Type > 8) {
+ break;
+ }
+ GdtEntry++;
+ }
+ ASSERT (Index != GdtEntryCount);
+ return Index * 8;
+}
+
+/**
+ Reset an AP when in SEV-ES mode.
+
+ If successful, this function never returns.
+
+ @param[in] Ghcb Pointer to the GHCB
+ @param[in] CpuMpData Pointer to CPU MP Data
+
+**/
+STATIC
+VOID
+MpInitLibSevEsAPReset (
+ IN GHCB *Ghcb,
+ IN CPU_MP_DATA *CpuMpData
+ )
+{
+ UINT16 Code16, Code32;
+ AP_RESET *APResetFn;
+ UINTN BufferStart;
+ UINTN StackStart;
+
+ Code16 = GetProtectedMode16CS ();
+ Code32 = GetProtectedMode32CS ();
+
+ if (CpuMpData->WakeupBufferHigh != 0) {
+ APResetFn = (AP_RESET *) (CpuMpData->WakeupBufferHigh + CpuMpData->AddressMap.SwitchToRealNoNxOffset);
+ } else {
+ APResetFn = (AP_RESET *) (CpuMpData->MpCpuExchangeInfo->BufferStart + CpuMpData->AddressMap.SwitchToRealOffset);
+ }
+
+ BufferStart = CpuMpData->MpCpuExchangeInfo->BufferStart;
+ StackStart = CpuMpData->SevEsAPResetStackStart -
+ (AP_RESET_STACK_SIZE * GetApicId ());
+
+ //
+ // This call never returns.
+ //
+ APResetFn (BufferStart, Code16, Code32, StackStart);
+}
+
+/**
This function will be called from AP reset code if BSP uses WakeUpAP.
@param[in] ExchangeInfo Pointer to the MP exchange info buffer
@@ -648,7 +765,14 @@ ApWakeupFunction ( InitializeApData (CpuMpData, ProcessorNumber, BistData, ApTopOfStack);
ApStartupSignalBuffer = CpuMpData->CpuData[ProcessorNumber].StartupApSignal;
- InterlockedDecrement ((UINT32 *) &CpuMpData->MpCpuExchangeInfo->NumApsExecuting);
+ //
+ // Delay decrementing the APs executing count when SEV-ES is enabled
+ // to allow the APs to issue an AP_RESET_HOLD before the BSP possibly
+ // performs another INIT-SIPI-SIPI sequence.
+ //
+ if (!CpuMpData->SevEsIsEnabled) {
+ InterlockedDecrement ((UINT32 *) &CpuMpData->MpCpuExchangeInfo->NumApsExecuting);
+ }
} else {
//
// Execute AP function if AP is ready
@@ -755,7 +879,52 @@ ApWakeupFunction ( //
while (TRUE) {
DisableInterrupts ();
- CpuSleep ();
+ if (CpuMpData->SevEsIsEnabled) {
+ MSR_SEV_ES_GHCB_REGISTER Msr;
+ GHCB *Ghcb;
+ UINT64 Status;
+ BOOLEAN DoDecrement;
+
+ if (CpuMpData->InitFlag == ApInitConfig) {
+ DoDecrement = TRUE;
+ }
+
+ while (TRUE) {
+ Msr.GhcbPhysicalAddress = AsmReadMsr64 (MSR_SEV_ES_GHCB);
+ Ghcb = Msr.Ghcb;
+
+ VmgInit (Ghcb);
+
+ if (DoDecrement) {
+ DoDecrement = FALSE;
+
+ //
+ // Perform the delayed decrement just before issuing the first
+ // VMGEXIT with AP_RESET_HOLD.
+ //
+ InterlockedDecrement ((UINT32 *) &CpuMpData->MpCpuExchangeInfo->NumApsExecuting);
+ }
+
+ Status = VmgExit (Ghcb, SVM_EXIT_AP_RESET_HOLD, 0, 0);
+ if ((Status == 0) && (Ghcb->SaveArea.SwExitInfo2 != 0)) {
+ VmgDone (Ghcb);
+ break;
+ }
+
+ VmgDone (Ghcb);
+ }
+
+ //
+ // Awakened in a new phase? Use the new CpuMpData
+ //
+ if (CpuMpData->NewCpuMpData != NULL) {
+ CpuMpData = CpuMpData->NewCpuMpData;
+ }
+
+ MpInitLibSevEsAPReset (Ghcb, CpuMpData);
+ } else {
+ CpuSleep ();
+ }
CpuPause ();
}
}
@@ -868,6 +1037,9 @@ FillExchangeInfoData ( ExchangeInfo->Enable5LevelPaging = (BOOLEAN) (Cr4.Bits.LA57 == 1);
DEBUG ((DEBUG_INFO, "%a: 5-Level Paging = %d\n", gEfiCallerBaseName, ExchangeInfo->Enable5LevelPaging));
+ ExchangeInfo->SevEsIsEnabled = CpuMpData->SevEsIsEnabled;
+ ExchangeInfo->GhcbBase = (UINTN) CpuMpData->GhcbBase;
+
//
// Get the BSP's data of GDT and IDT
//
@@ -894,8 +1066,9 @@ FillExchangeInfoData ( // EfiBootServicesCode to avoid page fault if NX memory protection is enabled.
//
if (CpuMpData->WakeupBufferHigh != 0) {
- Size = CpuMpData->AddressMap.RendezvousFunnelSize -
- CpuMpData->AddressMap.ModeTransitionOffset;
+ Size = CpuMpData->AddressMap.RendezvousFunnelSize +
+ CpuMpData->AddressMap.SwitchToRealSize -
+ CpuMpData->AddressMap.ModeTransitionOffset;
CopyMem (
(VOID *)CpuMpData->WakeupBufferHigh,
CpuMpData->AddressMap.RendezvousFunnelAddress +
@@ -948,7 +1121,8 @@ BackupAndPrepareWakeupBuffer( CopyMem (
(VOID *) CpuMpData->WakeupBuffer,
(VOID *) CpuMpData->AddressMap.RendezvousFunnelAddress,
- CpuMpData->AddressMap.RendezvousFunnelSize
+ CpuMpData->AddressMap.RendezvousFunnelSize +
+ CpuMpData->AddressMap.SwitchToRealSize
);
}
@@ -970,6 +1144,44 @@ RestoreWakeupBuffer( }
/**
+ Calculate the size of the reset stack.
+
+ @return Total amount of memory required for stacks
+**/
+STATIC
+UINTN
+GetApResetStackSize (
+ VOID
+ )
+{
+ return AP_RESET_STACK_SIZE * PcdGet32(PcdCpuMaxLogicalProcessorNumber);
+}
+
+/**
+ Calculate the size of the reset vector.
+
+ @param[in] AddressMap The pointer to Address Map structure.
+
+ @return Total amount of memory required for the AP reset area
+**/
+STATIC
+UINTN
+GetApResetVectorSize (
+ IN MP_ASSEMBLY_ADDRESS_MAP *AddressMap
+ )
+{
+ UINTN Size;
+
+ Size = ALIGN_VALUE (AddressMap->RendezvousFunnelSize +
+ AddressMap->SwitchToRealSize +
+ sizeof (MP_CPU_EXCHANGE_INFO),
+ CPU_STACK_ALIGNMENT);
+ Size += GetApResetStackSize ();
+
+ return Size;
+}
+
+/**
Allocate reset vector buffer.
@param[in, out] CpuMpData The pointer to CPU MP Data structure.
@@ -982,16 +1194,22 @@ AllocateResetVector ( UINTN ApResetVectorSize;
if (CpuMpData->WakeupBuffer == (UINTN) -1) {
- ApResetVectorSize = CpuMpData->AddressMap.RendezvousFunnelSize +
- sizeof (MP_CPU_EXCHANGE_INFO);
+ ApResetVectorSize = GetApResetVectorSize (&CpuMpData->AddressMap);
CpuMpData->WakeupBuffer = GetWakeupBuffer (ApResetVectorSize);
CpuMpData->MpCpuExchangeInfo = (MP_CPU_EXCHANGE_INFO *) (UINTN)
- (CpuMpData->WakeupBuffer + CpuMpData->AddressMap.RendezvousFunnelSize);
+ (CpuMpData->WakeupBuffer +
+ CpuMpData->AddressMap.RendezvousFunnelSize +
+ CpuMpData->AddressMap.SwitchToRealSize);
CpuMpData->WakeupBufferHigh = GetModeTransitionBuffer (
- CpuMpData->AddressMap.RendezvousFunnelSize -
+ CpuMpData->AddressMap.RendezvousFunnelSize +
+ CpuMpData->AddressMap.SwitchToRealSize -
CpuMpData->AddressMap.ModeTransitionOffset
);
+ //
+ // The reset stack starts at the end of the buffer.
+ //
+ CpuMpData->SevEsAPResetStackStart = CpuMpData->WakeupBuffer + ApResetVectorSize;
}
BackupAndPrepareWakeupBuffer (CpuMpData);
}
@@ -1006,7 +1224,80 @@ FreeResetVector ( IN CPU_MP_DATA *CpuMpData
)
{
- RestoreWakeupBuffer (CpuMpData);
+ //
+ // If SEV-ES is enabled, the reset area is needed for AP parking and
+ // and AP startup in the OS, so the reset area is reserved. Do not
+ // perform the restore as this will overwrite memory which has data
+ // needed by SEV-ES.
+ //
+ if (!CpuMpData->SevEsIsEnabled) {
+ RestoreWakeupBuffer (CpuMpData);
+ }
+}
+
+/**
+ Allocate the SEV-ES AP jump table buffer.
+
+ @param[in, out] CpuMpData The pointer to CPU MP Data structure.
+**/
+VOID
+AllocateSevEsAPMemory (
+ IN OUT CPU_MP_DATA *CpuMpData
+ )
+{
+ if (CpuMpData->SevEsAPBuffer == (UINTN) -1) {
+ CpuMpData->SevEsAPBuffer =
+ CpuMpData->SevEsIsEnabled ? GetSevEsAPMemory () : 0;
+ }
+}
+
+/**
+ Program the SEV-ES AP jump table buffer.
+
+ @param[in] SipiVector The SIPI vector used for the AP Reset
+**/
+VOID
+SetSevEsJumpTable (
+ IN UINTN SipiVector
+ )
+{
+ SEV_ES_AP_JMP_FAR *JmpFar;
+ UINT32 Offset, InsnByte;
+ UINT8 LoNib, HiNib;
+
+ JmpFar = (SEV_ES_AP_JMP_FAR *) FixedPcdGet32 (PcdSevEsWorkAreaBase);
+ ASSERT (JmpFar != NULL);
+
+ //
+ // Obtain the address of the Segment/Rip location in the workarea.
+ // This will be set to a value derived from the SIPI vector and will
+ // be the memory address used for the far jump below.
+ //
+ Offset = FixedPcdGet32 (PcdSevEsWorkAreaBase);
+ Offset += sizeof (JmpFar->InsnBuffer);
+ LoNib = (UINT8) Offset;
+ HiNib = (UINT8) (Offset >> 8);
+
+ //
+ // Program the workarea (which is the initial AP boot address) with
+ // far jump to the SIPI vector (where XX and YY represent the
+ // address of where the SIPI vector is stored.
+ //
+ // JMP FAR [CS:XXYY] => 2E FF 2E YY XX
+ //
+ InsnByte = 0;
+ JmpFar->InsnBuffer[InsnByte++] = 0x2E; // CS override prefix
+ JmpFar->InsnBuffer[InsnByte++] = 0xFF; // JMP (FAR)
+ JmpFar->InsnBuffer[InsnByte++] = 0x2E; // ModRM (JMP memory location)
+ JmpFar->InsnBuffer[InsnByte++] = LoNib; // YY offset ...
+ JmpFar->InsnBuffer[InsnByte++] = HiNib; // XX offset ...
+
+ //
+ // Program the Segment/Rip based on the SIPI vector (always at least
+ // 16-byte aligned, so Rip is set to 0).
+ //
+ JmpFar->Rip = 0;
+ JmpFar->Segment = (UINT16) (SipiVector >> 4);
}
/**
@@ -1043,6 +1334,7 @@ WakeUpAP ( CpuMpData->InitFlag != ApInitDone) {
ResetVectorRequired = TRUE;
AllocateResetVector (CpuMpData);
+ AllocateSevEsAPMemory (CpuMpData);
FillExchangeInfoData (CpuMpData);
SaveLocalApicTimerSetting (CpuMpData);
}
@@ -1080,6 +1372,15 @@ WakeUpAP ( }
if (ResetVectorRequired) {
//
+ // For SEV-ES, the initial AP boot address will be defined by
+ // PcdSevEsWorkAreaBase. The Segment/Rip must be the jump address
+ // from the original INIT-SIPI-SIPI.
+ //
+ if (CpuMpData->SevEsIsEnabled) {
+ SetSevEsJumpTable (ExchangeInfo->BufferStart);
+ }
+
+ //
// Wakeup all APs
//
SendInitSipiSipiAllExcludingSelf ((UINT32) ExchangeInfo->BufferStart);
@@ -1170,6 +1471,16 @@ WakeUpAP ( *(UINT32 *) CpuData->StartupApSignal = WAKEUP_AP_SIGNAL;
if (ResetVectorRequired) {
CpuInfoInHob = (CPU_INFO_IN_HOB *) (UINTN) CpuMpData->CpuInfoInHob;
+
+ //
+ // For SEV-ES, the initial AP boot address will be defined by
+ // PcdSevEsWorkAreaBase. The Segment/Rip must be the jump address
+ // from the original INIT-SIPI-SIPI.
+ //
+ if (CpuMpData->SevEsIsEnabled) {
+ SetSevEsJumpTable (ExchangeInfo->BufferStart);
+ }
+
SendInitSipiSipi (
CpuInfoInHob[ProcessorNumber].ApicId,
(UINT32) ExchangeInfo->BufferStart
@@ -1646,7 +1957,7 @@ MpInitLibInitialize ( ASSERT (MaxLogicalProcessorNumber != 0);
AsmGetAddressMap (&AddressMap);
- ApResetVectorSize = AddressMap.RendezvousFunnelSize + sizeof (MP_CPU_EXCHANGE_INFO);
+ ApResetVectorSize = GetApResetVectorSize (&AddressMap);
ApStackSize = PcdGet32(PcdCpuApStackSize);
ApLoopMode = GetApLoopMode (&MonitorFilterSize);
@@ -1705,6 +2016,8 @@ MpInitLibInitialize ( CpuMpData->CpuInfoInHob = (UINT64) (UINTN) (CpuMpData->CpuData + MaxLogicalProcessorNumber);
InitializeSpinLock(&CpuMpData->MpLock);
CpuMpData->SevEsIsEnabled = PcdGetBool (PcdSevEsIsEnabled);
+ CpuMpData->SevEsAPBuffer = (UINTN) -1;
+ CpuMpData->GhcbBase = PcdGet64 (PcdGhcbBase);
//
// Make sure no memory usage outside of the allocated buffer.
@@ -1763,6 +2076,7 @@ MpInitLibInitialize ( // APs have been wakeup before, just get the CPU Information
// from HOB
//
+ OldCpuMpData->NewCpuMpData = CpuMpData;
CpuMpData->CpuCount = OldCpuMpData->CpuCount;
CpuMpData->BspNumber = OldCpuMpData->BspNumber;
CpuMpData->CpuInfoInHob = OldCpuMpData->CpuInfoInHob;
diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.h b/UefiCpuPkg/Library/MpInitLib/MpLib.h index 5b46c295b6..b1a9d99cb3 100644 --- a/UefiCpuPkg/Library/MpInitLib/MpLib.h +++ b/UefiCpuPkg/Library/MpInitLib/MpLib.h @@ -173,6 +173,11 @@ typedef struct { UINT8 *RelocateApLoopFuncAddress;
UINTN RelocateApLoopFuncSize;
UINTN ModeTransitionOffset;
+ UINTN SwitchToRealSize;
+ UINTN SwitchToRealOffset;
+ UINTN SwitchToRealNoNxOffset;
+ UINTN SwitchToRealPM16ModeOffset;
+ UINTN SwitchToRealPM16ModeSize;
} MP_ASSEMBLY_ADDRESS_MAP;
typedef struct _CPU_MP_DATA CPU_MP_DATA;
@@ -211,6 +216,8 @@ typedef struct { // Enable5LevelPaging indicates whether 5-level paging is enabled in long mode.
//
BOOLEAN Enable5LevelPaging;
+ BOOLEAN SevEsIsEnabled;
+ UINTN GhcbBase;
} MP_CPU_EXCHANGE_INFO;
#pragma pack()
@@ -257,6 +264,7 @@ struct _CPU_MP_DATA { UINT8 ApLoopMode;
UINT8 ApTargetCState;
UINT16 PmCodeSegment;
+ UINT16 Pm16CodeSegment;
CPU_AP_DATA *CpuData;
volatile MP_CPU_EXCHANGE_INFO *MpCpuExchangeInfo;
@@ -278,8 +286,47 @@ struct _CPU_MP_DATA { BOOLEAN WakeUpByInitSipiSipi;
BOOLEAN SevEsIsEnabled;
+ UINTN SevEsAPBuffer;
+ UINTN SevEsAPResetStackStart;
+ CPU_MP_DATA *NewCpuMpData;
+
+ UINT64 GhcbBase;
};
+#define AP_RESET_STACK_SIZE 64
+
+#pragma pack(1)
+
+typedef struct {
+ UINT8 InsnBuffer[8];
+ UINT16 Rip;
+ UINT16 Segment;
+} SEV_ES_AP_JMP_FAR;
+
+#pragma pack()
+
+/**
+ Assembly code to move an AP from long mode to real mode.
+
+ Move an AP from long mode to real mode in preparation to invoking
+ the reset vector. This is used for SEV-ES guests where a hypervisor
+ is not allowed to set the CS and RIP to point to the reset vector.
+
+ @param[in] BufferStart The reset vector target.
+ @param[in] Code16 16-bit protected mode code segment value.
+ @param[in] Code32 32-bit protected mode code segment value.
+ @param[in] StackStart The start of a stack to be used for transitioning
+ from long mode to real mode.
+**/
+typedef
+VOID
+(EFIAPI AP_RESET) (
+ IN UINTN BufferStart,
+ IN UINT16 Code16,
+ IN UINT16 Code32,
+ IN UINTN StackStart
+ );
+
extern EFI_GUID mCpuInitMpLibHobGuid;
/**
@@ -386,6 +433,19 @@ GetModeTransitionBuffer ( );
/**
+ Return the address of the SEV-ES AP jump table.
+
+ This buffer is required in order for an SEV-ES guest to transition from
+ UEFI into an OS.
+
+ @return Return SEV-ES AP jump table buffer
+**/
+UINTN
+GetSevEsAPMemory (
+ VOID
+ );
+
+/**
This function will be called by BSP to wakeup AP.
@param[in] CpuMpData Pointer to CPU MP Data
diff --git a/UefiCpuPkg/Library/MpInitLib/PeiMpInitLib.inf b/UefiCpuPkg/Library/MpInitLib/PeiMpInitLib.inf index 4b3d39fbf3..34abf25d43 100644 --- a/UefiCpuPkg/Library/MpInitLib/PeiMpInitLib.inf +++ b/UefiCpuPkg/Library/MpInitLib/PeiMpInitLib.inf @@ -51,6 +51,7 @@ SynchronizationLib
PeiServicesLib
PcdLib
+ VmgExitLib
[Pcd]
gUefiCpuPkgTokenSpaceGuid.PcdCpuMaxLogicalProcessorNumber ## CONSUMES
@@ -62,6 +63,8 @@ gUefiCpuPkgTokenSpaceGuid.PcdCpuApLoopMode ## CONSUMES
gUefiCpuPkgTokenSpaceGuid.PcdCpuApTargetCstate ## SOMETIMES_CONSUMES
gUefiCpuPkgTokenSpaceGuid.PcdSevEsIsEnabled ## CONSUMES
+ gUefiCpuPkgTokenSpaceGuid.PcdSevEsWorkAreaBase ## SOMETIMES_CONSUMES
+ gEfiMdeModulePkgTokenSpaceGuid.PcdGhcbBase ## CONSUMES
[Ppis]
gEdkiiPeiShadowMicrocodePpiGuid ## SOMETIMES_CONSUMES
diff --git a/UefiCpuPkg/Library/MpInitLib/PeiMpLib.c b/UefiCpuPkg/Library/MpInitLib/PeiMpLib.c index a548fed23f..3989bd6a7a 100644 --- a/UefiCpuPkg/Library/MpInitLib/PeiMpLib.c +++ b/UefiCpuPkg/Library/MpInitLib/PeiMpLib.c @@ -281,6 +281,25 @@ GetModeTransitionBuffer ( }
/**
+ Return the address of the SEV-ES AP jump table.
+
+ This buffer is required in order for an SEV-ES guest to transition from
+ UEFI into an OS.
+
+ @return Return SEV-ES AP jump table buffer
+**/
+UINTN
+GetSevEsAPMemory (
+ VOID
+ )
+{
+ //
+ // PEI phase doesn't need to do such transition. So simply return 0.
+ //
+ return 0;
+}
+
+/**
Checks APs status and updates APs status if needed.
**/
diff --git a/UefiCpuPkg/Library/MpInitLib/X64/MpEqu.inc b/UefiCpuPkg/Library/MpInitLib/X64/MpEqu.inc index 58ef369342..c92daaaffd 100644 --- a/UefiCpuPkg/Library/MpInitLib/X64/MpEqu.inc +++ b/UefiCpuPkg/Library/MpInitLib/X64/MpEqu.inc @@ -19,7 +19,7 @@ CPU_SWITCH_STATE_IDLE equ 0 CPU_SWITCH_STATE_STORED equ 1
CPU_SWITCH_STATE_LOADED equ 2
-LockLocation equ (RendezvousFunnelProcEnd - RendezvousFunnelProcStart)
+LockLocation equ (SwitchToRealProcEnd - RendezvousFunnelProcStart)
StackStartAddressLocation equ LockLocation + 08h
StackSizeLocation equ LockLocation + 10h
ApProcedureLocation equ LockLocation + 18h
@@ -41,3 +41,5 @@ ModeTransitionSegmentLocation equ LockLocation + 98h ModeHighMemoryLocation equ LockLocation + 9Ah
ModeHighSegmentLocation equ LockLocation + 9Eh
Enable5LevelPagingLocation equ LockLocation + 0A0h
+SevEsIsEnabledLocation equ LockLocation + 0A1h
+GhcbBaseLocation equ LockLocation + 0A2h
diff --git a/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm b/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm index 87f2523e85..6956b408d0 100644 --- a/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm +++ b/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm @@ -184,9 +184,97 @@ Releaselock: add edi, StackStartAddressLocation
add rax, qword [edi]
mov rsp, rax
+
+ lea edi, [esi + SevEsIsEnabledLocation]
+ cmp byte [edi], 1 ; SevEsIsEnabled
+ jne CProcedureInvoke
+
+ ;
+ ; program GHCB
+ ; Each page after the GHCB is a per-CPU page, so the calculation programs
+ ; a GHCB to be every 8KB.
+ ;
+ mov eax, SIZE_4KB
+ shl eax, 1 ; EAX = SIZE_4K * 2
+ mov ecx, ebx
+ mul ecx ; EAX = SIZE_4K * 2 * CpuNumber
+ mov edi, esi
+ add edi, GhcbBaseLocation
+ add rax, qword [edi]
+ mov rdx, rax
+ shr rdx, 32
+ mov rcx, 0xc0010130
+ wrmsr
jmp CProcedureInvoke
GetApicId:
+ lea edi, [esi + SevEsIsEnabledLocation]
+ cmp byte [edi], 1 ; SevEsIsEnabled
+ jne DoCpuid
+
+ ;
+ ; Since we don't have a stack yet, we can't take a #VC
+ ; exception. Use the GHCB protocol to perform the CPUID
+ ; calls.
+ ;
+ mov rcx, 0xc0010130
+ rdmsr
+ shl rdx, 32
+ or rax, rdx
+ mov rdi, rax ; RDI now holds the original GHCB GPA
+
+ mov rdx, 0 ; CPUID function 0
+ mov rax, 0 ; RAX register requested
+ or rax, 4
+ wrmsr
+ rep vmmcall
+ rdmsr
+ cmp edx, 0bh
+ jb NoX2ApicSevEs ; CPUID level below CPUID_EXTENDED_TOPOLOGY
+
+ mov rdx, 0bh ; CPUID function 0x0b
+ mov rax, 040000000h ; RBX register requested
+ or rax, 4
+ wrmsr
+ rep vmmcall
+ rdmsr
+ test edx, 0ffffh
+ jz NoX2ApicSevEs ; CPUID.0BH:EBX[15:0] is zero
+
+ mov rdx, 0bh ; CPUID function 0x0b
+ mov rax, 0c0000000h ; RDX register requested
+ or rax, 4
+ wrmsr
+ rep vmmcall
+ rdmsr
+
+ ; Processor is x2APIC capable; 32-bit x2APIC ID is now in EDX
+ jmp RestoreGhcb
+
+NoX2ApicSevEs:
+ ; Processor is not x2APIC capable, so get 8-bit APIC ID
+ mov rdx, 1 ; CPUID function 1
+ mov rax, 040000000h ; RBX register requested
+ or rax, 4
+ wrmsr
+ rep vmmcall
+ rdmsr
+ shr edx, 24
+
+RestoreGhcb:
+ mov rbx, rdx ; Save x2APIC/APIC ID
+
+ mov rdx, rdi ; RDI holds the saved GHCB GPA
+ shr rdx, 32
+ mov eax, edi
+ wrmsr
+
+ mov rdx, rbx
+
+ ; x2APIC ID or APIC ID is in EDX
+ jmp GetProcessorNumber
+
+DoCpuid:
mov eax, 0
cpuid
cmp eax, 0bh
@@ -254,11 +342,157 @@ CProcedureInvoke: RendezvousFunnelProcEnd:
;-------------------------------------------------------------------------------------
+;SwitchToRealProc procedure follows.
+;ALSO THIS PROCEDURE IS EXECUTED BY APs TRANSITIONING TO 16 BIT MODE. HENCE THIS PROC
+;IS IN MACHINE CODE.
+; SwitchToRealProc (UINTN BufferStart, UINT16 Code16, UINT16 Code32, UINTN StackStart)
+; rcx - Buffer Start
+; rdx - Code16 Selector Offset
+; r8 - Code32 Selector Offset
+; r9 - Stack Start
+;-------------------------------------------------------------------------------------
+global ASM_PFX(SwitchToRealProc)
+ASM_PFX(SwitchToRealProc):
+SwitchToRealProcStart:
+BITS 64
+ cli
+
+ ;
+ ; Get RDX reset value before changing stacks since the
+ ; new stack won't be able to accomodate a #VC exception.
+ ;
+ push rax
+ push rbx
+ push rcx
+ push rdx
+
+ mov rax, 1
+ cpuid
+ mov rsi, rax ; Save off the reset value for RDX
+
+ pop rdx
+ pop rcx
+ pop rbx
+ pop rax
+
+ ;
+ ; Establish stack below 1MB
+ ;
+ mov rsp, r9
+
+ ;
+ ; Push ultimate Reset Vector onto the stack
+ ;
+ mov rax, rcx
+ shr rax, 4
+ push word 0x0002 ; RFLAGS
+ push ax ; CS
+ push word 0x0000 ; RIP
+ push word 0x0000 ; For alignment, will be discarded
+
+ ;
+ ; Get address of "16-bit operand size" label
+ ;
+ lea rbx, [PM16Mode]
+
+ ;
+ ; Push addresses used to change to compatibility mode
+ ;
+ lea rax, [CompatMode]
+ push r8
+ push rax
+
+ ;
+ ; Clear R8 - R15, for reset, before going into 32-bit mode
+ ;
+ xor r8, r8
+ xor r9, r9
+ xor r10, r10
+ xor r11, r11
+ xor r12, r12
+ xor r13, r13
+ xor r14, r14
+ xor r15, r15
+
+ ;
+ ; Far return into 32-bit mode
+ ;
+o64 retf
+
+BITS 32
+CompatMode:
+ ;
+ ; Set up stack to prepare for exiting protected mode
+ ;
+ push edx ; Code16 CS
+ push ebx ; PM16Mode label address
+
+ ;
+ ; Disable paging
+ ;
+ mov eax, cr0 ; Read CR0
+ btr eax, 31 ; Set PG=0
+ mov cr0, eax ; Write CR0
+
+ ;
+ ; Disable long mode
+ ;
+ mov ecx, 0c0000080h ; EFER MSR number
+ rdmsr ; Read EFER
+ btr eax, 8 ; Set LME=0
+ wrmsr ; Write EFER
+
+ ;
+ ; Disable PAE
+ ;
+ mov eax, cr4 ; Read CR4
+ btr eax, 5 ; Set PAE=0
+ mov cr4, eax ; Write CR4
+
+ mov edx, esi ; Restore RDX reset value
+
+ ;
+ ; Switch to 16-bit operand size
+ ;
+ retf
+
+BITS 16
+ ;
+ ; At entry to this label
+ ; - RDX will have its reset value
+ ; - On the top of the stack
+ ; - Alignment data (two bytes) to be discarded
+ ; - IP for Real Mode (two bytes)
+ ; - CS for Real Mode (two bytes)
+ ;
+PM16Mode:
+ mov eax, cr0 ; Read CR0
+ btr eax, 0 ; Set PE=0
+ mov cr0, eax ; Write CR0
+
+ pop ax ; Discard alignment data
+
+ ;
+ ; Clear registers (except RDX and RSP) before going into 16-bit mode
+ ;
+ xor eax, eax
+ xor ebx, ebx
+ xor ecx, ecx
+ xor esi, esi
+ xor edi, edi
+ xor ebp, ebp
+
+ iret
+
+SwitchToRealProcEnd:
+
+;-------------------------------------------------------------------------------------
; AsmRelocateApLoop (MwaitSupport, ApTargetCState, PmCodeSegment, TopOfApStack, CountTofinish);
;-------------------------------------------------------------------------------------
global ASM_PFX(AsmRelocateApLoop)
ASM_PFX(AsmRelocateApLoop):
AsmRelocateApLoopStart:
+BITS 64
cli ; Disable interrupt before switching to 32-bit mode
mov rax, [rsp + 40] ; CountTofinish
lock dec dword [rax] ; (*CountTofinish)--
@@ -324,6 +558,11 @@ ASM_PFX(AsmGetAddressMap): mov qword [rcx + 18h], rax
mov qword [rcx + 20h], AsmRelocateApLoopEnd - AsmRelocateApLoopStart
mov qword [rcx + 28h], Flat32Start - RendezvousFunnelProcStart
+ mov qword [rcx + 30h], SwitchToRealProcEnd - SwitchToRealProcStart ; SwitchToRealSize
+ mov qword [rcx + 38h], SwitchToRealProcStart - RendezvousFunnelProcStart ; SwitchToRealOffset
+ mov qword [rcx + 40h], SwitchToRealProcStart - Flat32Start ; SwitchToRealNoNxOffset
+ mov qword [rcx + 48h], PM16Mode - RendezvousFunnelProcStart ; SwitchToRealPM16ModeOffset
+ mov qword [rcx + 50h], SwitchToRealProcEnd - PM16Mode ; SwitchToRealPM16ModeSize
ret
;-------------------------------------------------------------------------------------
diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmmFuncsArch.c b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmmFuncsArch.c index 6298571e29..28f8e8e133 100644 --- a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmmFuncsArch.c +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmmFuncsArch.c @@ -121,7 +121,7 @@ GetProtectedModeCS ( GdtEntry = (IA32_SEGMENT_DESCRIPTOR *) GdtrDesc.Base;
for (Index = 0; Index < GdtEntryCount; Index++) {
if (GdtEntry->Bits.L == 0) {
- if (GdtEntry->Bits.Type > 8 && GdtEntry->Bits.L == 0) {
+ if (GdtEntry->Bits.Type > 8 && GdtEntry->Bits.DB == 1) {
break;
}
}
|