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OvmfPkg/VmgExitLib: Implement library support for VmgExitLib in OVMF 

The base VmgExitLib library provides a default limited interface. As it
does not provide full support, create an OVMF version of this library to
begin the process of providing full support of SEV-ES within OVMF.

SEV-ES support is only provided for X64 builds, so only OvmfPkgX64.dsc is
updated to make use of the OvmfPkg version of the library.

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Regression-tested-by: Laszlo Ersek <lersek@redhat.com>
This commit is contained in:
Tom Lendacky 2020-08-12 15:21:36 -05:00 committed by mergify[bot]
parent 5277540e37
commit 61bacc0fa1
4 changed files with 277 additions and 1 deletions
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159
OvmfPkg/Library/VmgExitLib/VmgExitLib.c Normal file
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/** @file
VMGEXIT Support Library.
Copyright (C) 2020, Advanced Micro Devices, Inc. All rights reserved.<BR>
SPDX-License-Identifier: BSD-2-Clause-Patent
**/
#include <Base.h>
#include <Uefi.h>
#include <Library/BaseMemoryLib.h>
#include <Library/VmgExitLib.h>
#include <Register/Amd/Msr.h>
/**
Check for VMGEXIT error
Check if the hypervisor has returned an error after completion of the VMGEXIT
by examining the SwExitInfo1 field of the GHCB.
@param[in] Ghcb A pointer to the GHCB
@retval 0 VMGEXIT succeeded.
@return Exception number to be propagated, VMGEXIT processing
did not succeed.
**/
STATIC
UINT64
VmgExitErrorCheck (
IN GHCB *Ghcb
)
{
GHCB_EVENT_INJECTION Event;
GHCB_EXIT_INFO ExitInfo;
UINT64 Status;
ExitInfo.Uint64 = Ghcb->SaveArea.SwExitInfo1;
ASSERT ((ExitInfo.Elements.Lower32Bits == 0) ||
(ExitInfo.Elements.Lower32Bits == 1));
Status = 0;
if (ExitInfo.Elements.Lower32Bits == 0) {
return Status;
}
if (ExitInfo.Elements.Lower32Bits == 1) {
ASSERT (Ghcb->SaveArea.SwExitInfo2 != 0);
//
// Check that the return event is valid
//
Event.Uint64 = Ghcb->SaveArea.SwExitInfo2;
if (Event.Elements.Valid &&
Event.Elements.Type == GHCB_EVENT_INJECTION_TYPE_EXCEPTION) {
switch (Event.Elements.Vector) {
case GP_EXCEPTION:
case UD_EXCEPTION:
//
// Use returned event as return code
//
Status = Event.Uint64;
}
}
}
if (Status == 0) {
GHCB_EVENT_INJECTION GpEvent;
GpEvent.Uint64 = 0;
GpEvent.Elements.Vector = GP_EXCEPTION;
GpEvent.Elements.Type = GHCB_EVENT_INJECTION_TYPE_EXCEPTION;
GpEvent.Elements.Valid = 1;
Status = GpEvent.Uint64;
}
return Status;
}
/**
Perform VMGEXIT.
Sets the necessary fields of the GHCB, invokes the VMGEXIT instruction and
then handles the return actions.
@param[in, out] Ghcb A pointer to the GHCB
@param[in] ExitCode VMGEXIT code to be assigned to the SwExitCode
field of the GHCB.
@param[in] ExitInfo1 VMGEXIT information to be assigned to the
SwExitInfo1 field of the GHCB.
@param[in] ExitInfo2 VMGEXIT information to be assigned to the
SwExitInfo2 field of the GHCB.
@retval 0 VMGEXIT succeeded.
@return Exception number to be propagated, VMGEXIT
processing did not succeed.
**/
UINT64
EFIAPI
VmgExit (
IN OUT GHCB *Ghcb,
IN UINT64 ExitCode,
IN UINT64 ExitInfo1,
IN UINT64 ExitInfo2
)
{
Ghcb->SaveArea.SwExitCode = ExitCode;
Ghcb->SaveArea.SwExitInfo1 = ExitInfo1;
Ghcb->SaveArea.SwExitInfo2 = ExitInfo2;
//
// Guest memory is used for the guest-hypervisor communication, so fence
// the invocation of the VMGEXIT instruction to ensure GHCB accesses are
// synchronized properly.
//
MemoryFence ();
AsmVmgExit ();
MemoryFence ();
return VmgExitErrorCheck (Ghcb);
}
/**
Perform pre-VMGEXIT initialization/preparation.
Performs the necessary steps in preparation for invoking VMGEXIT. Must be
called before setting any fields within the GHCB.
@param[in, out] Ghcb A pointer to the GHCB
**/
VOID
EFIAPI
VmgInit (
IN OUT GHCB *Ghcb
)
{
SetMem (&Ghcb->SaveArea, sizeof (Ghcb->SaveArea), 0);
}
/**
Perform post-VMGEXIT cleanup.
Performs the necessary steps to cleanup after invoking VMGEXIT. Must be
called after obtaining needed fields within the GHCB.
@param[in, out] Ghcb A pointer to the GHCB
**/
VOID
EFIAPI
VmgDone (
IN OUT GHCB *Ghcb
)
{
}

36
OvmfPkg/Library/VmgExitLib/VmgExitLib.inf Normal file
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## @file
# VMGEXIT Support Library.
#
# Copyright (C) 2020, Advanced Micro Devices, Inc. All rights reserved.<BR>
# SPDX-License-Identifier: BSD-2-Clause-Patent
#
##
[Defines]
INF_VERSION = 0x00010005
BASE_NAME = VmgExitLib
FILE_GUID = 0e923c25-13cd-430b-8714-ffe85652a97b
MODULE_TYPE = BASE
VERSION_STRING = 1.0
LIBRARY_CLASS = VmgExitLib
#
# The following information is for reference only and not required by the build tools.
#
# VALID_ARCHITECTURES = X64
#
[Sources.common]
VmgExitLib.c
VmgExitVcHandler.c
[Packages]
MdePkg/MdePkg.dec
OvmfPkg/OvmfPkg.dec
UefiCpuPkg/UefiCpuPkg.dec
[LibraryClasses]
BaseLib
BaseMemoryLib
DebugLib

81
OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c Normal file
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/** @file
X64 #VC Exception Handler functon.
Copyright (C) 2020, Advanced Micro Devices, Inc. All rights reserved.<BR>
SPDX-License-Identifier: BSD-2-Clause-Patent
**/
#include <Base.h>
#include <Uefi.h>
#include <Library/BaseMemoryLib.h>
#include <Library/VmgExitLib.h>
#include <Register/Amd/Msr.h>
/**
Handle a #VC exception.
Performs the necessary processing to handle a #VC exception.
@param[in, out] ExceptionType Pointer to an EFI_EXCEPTION_TYPE to be set
as value to use on error.
@param[in, out] SystemContext Pointer to EFI_SYSTEM_CONTEXT
@retval EFI_SUCCESS Exception handled
@retval EFI_UNSUPPORTED #VC not supported, (new) exception value to
propagate provided
@retval EFI_PROTOCOL_ERROR #VC handling failed, (new) exception value to
propagate provided
**/
EFI_STATUS
EFIAPI
VmgExitHandleVc (
IN OUT EFI_EXCEPTION_TYPE *ExceptionType,
IN OUT EFI_SYSTEM_CONTEXT SystemContext
)
{
MSR_SEV_ES_GHCB_REGISTER Msr;
EFI_SYSTEM_CONTEXT_X64 *Regs;
GHCB *Ghcb;
UINT64 ExitCode, Status;
EFI_STATUS VcRet;
VcRet = EFI_SUCCESS;
Msr.GhcbPhysicalAddress = AsmReadMsr64 (MSR_SEV_ES_GHCB);
ASSERT (Msr.GhcbInfo.Function == 0);
ASSERT (Msr.Ghcb != 0);
Regs = SystemContext.SystemContextX64;
Ghcb = Msr.Ghcb;
VmgInit (Ghcb);
ExitCode = Regs->ExceptionData;
switch (ExitCode) {
default:
Status = VmgExit (Ghcb, SVM_EXIT_UNSUPPORTED, ExitCode, 0);
if (Status == 0) {
Regs->ExceptionData = 0;
*ExceptionType = GP_EXCEPTION;
} else {
GHCB_EVENT_INJECTION Event;
Event.Uint64 = Status;
if (Event.Elements.ErrorCodeValid != 0) {
Regs->ExceptionData = Event.Elements.ErrorCode;
} else {
Regs->ExceptionData = 0;
}
*ExceptionType = Event.Elements.Vector;
}
VcRet = EFI_PROTOCOL_ERROR;
}
VmgDone (Ghcb);
return VcRet;
}

2
OvmfPkg/OvmfPkgX64.dsc
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@ -233,7 +233,7 @@
[LibraryClasses.common]
BaseCryptLib|CryptoPkg/Library/BaseCryptLib/BaseCryptLib.inf
VmgExitLib|UefiCpuPkg/Library/VmgExitLibNull/VmgExitLibNull.inf
VmgExitLib|OvmfPkg/Library/VmgExitLib/VmgExitLib.inf
[LibraryClasses.common.SEC]
TimerLib|OvmfPkg/Library/AcpiTimerLib/BaseRomAcpiTimerLib.inf