On 11/21/19 5:15 AM, Laszlo Ersek via Groups.Io wrote:
> On 11/20/19 21:06, Lendacky, Thomas wrote:
>> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2198
>>
>> To support issuing a VMGEXIT instruction, create a library that can be
>> used to perform GHCB and VMGEXIT related operations and to issue the
>> actual VMGEXIT instruction when using the GHCB.
>>
>> Additionally, two VMGEXIT / MMIO related functions are created to support
>> flash emulation. Flash emulation currently is done by marking the flash
>> area as read-only and taking a nested page fault to perform the emulation
>> of the instruction. However, emulation cannot be performed because there
>> is no instruction decode assist support when SEV-ES is enabled. Provide
>> routines to initiate an MMIO request to perform actual writes to flash.
>>
>> Cc: Eric Dong <eric.d...@intel.com>
>> Cc: Ray Ni <ray...@intel.com>
>> Cc: Laszlo Ersek <ler...@redhat.com>
>> Signed-off-by: Tom Lendacky <thomas.lenda...@amd.com>
>> ---
>> UefiCpuPkg/UefiCpuPkg.dec | 3 +
>> UefiCpuPkg/UefiCpuPkg.dsc | 5 +
>> UefiCpuPkg/Library/VmgExitLib/VmgExitLib.inf | 33 +++++
>> UefiCpuPkg/Include/Library/VmgExitLib.h | 96 ++++++++++++++
>> UefiCpuPkg/Library/VmgExitLib/VmgExitLib.c | 132 +++++++++++++++++++
>> UefiCpuPkg/Library/VmgExitLib/VmgExitLib.uni | 15 +++
>> 6 files changed, 284 insertions(+)
>> create mode 100644 UefiCpuPkg/Library/VmgExitLib/VmgExitLib.inf
>> create mode 100644 UefiCpuPkg/Include/Library/VmgExitLib.h
>> create mode 100644 UefiCpuPkg/Library/VmgExitLib/VmgExitLib.c
>> create mode 100644 UefiCpuPkg/Library/VmgExitLib/VmgExitLib.uni
>>
>> diff --git a/UefiCpuPkg/UefiCpuPkg.dec b/UefiCpuPkg/UefiCpuPkg.dec
>> index 12f4413ea5b0..90feb9166dc8 100644
>> --- a/UefiCpuPkg/UefiCpuPkg.dec
>> +++ b/UefiCpuPkg/UefiCpuPkg.dec
>> @@ -53,6 +53,9 @@ [LibraryClasses.IA32, LibraryClasses.X64]
>> ##
>> MpInitLib|Include/Library/MpInitLib.h
>>
>> + ## @libraryclass Provides function to support VMGEXIT processing.
>> + VmgExitLib|Include/Library/VmgExitLib.h
>> +
>> [Guids]
>> gUefiCpuPkgTokenSpaceGuid = { 0xac05bf33, 0x995a, 0x4ed4, { 0xaa,
>> 0xb8, 0xef, 0x7a, 0xe8, 0xf, 0x5c, 0xb0 }}
>> gMsegSmramGuid = { 0x5802bce4, 0xeeee, 0x4e33, { 0xa1,
>> 0x30, 0xeb, 0xad, 0x27, 0xf0, 0xe4, 0x39 }}
>> diff --git a/UefiCpuPkg/UefiCpuPkg.dsc b/UefiCpuPkg/UefiCpuPkg.dsc
>> index d28cb5cccb52..5ab7e423e8ab 100644
>> --- a/UefiCpuPkg/UefiCpuPkg.dsc
>> +++ b/UefiCpuPkg/UefiCpuPkg.dsc
>> @@ -63,6 +63,7 @@ [LibraryClasses.common.SEC]
>> HobLib|MdePkg/Library/PeiHobLib/PeiHobLib.inf
>>
>> PeiServicesTablePointerLib|MdePkg/Library/PeiServicesTablePointerLibIdt/PeiServicesTablePointerLibIdt.inf
>>
>> MemoryAllocationLib|MdePkg/Library/PeiMemoryAllocationLib/PeiMemoryAllocationLib.inf
>> + VmgExitLib|UefiCpuPkg/Library/VmgExitLib/VmgExitLib.inf
>>
>> [LibraryClasses.common.PEIM]
>>
>> MemoryAllocationLib|MdePkg/Library/PeiMemoryAllocationLib/PeiMemoryAllocationLib.inf
>> @@ -74,6 +75,7 @@ [LibraryClasses.common.PEIM]
>> [LibraryClasses.IA32.PEIM, LibraryClasses.X64.PEIM]
>>
>> PeiServicesTablePointerLib|MdePkg/Library/PeiServicesTablePointerLibIdt/PeiServicesTablePointerLibIdt.inf
>>
>> CpuExceptionHandlerLib|UefiCpuPkg/Library/CpuExceptionHandlerLib/PeiCpuExceptionHandlerLib.inf
>> + VmgExitLib|UefiCpuPkg/Library/VmgExitLib/VmgExitLib.inf
>>
>> [LibraryClasses.common.DXE_DRIVER]
>>
>> MemoryAllocationLib|MdePkg/Library/UefiMemoryAllocationLib/UefiMemoryAllocationLib.inf
>> @@ -81,12 +83,14 @@ [LibraryClasses.common.DXE_DRIVER]
>>
>> CpuExceptionHandlerLib|UefiCpuPkg/Library/CpuExceptionHandlerLib/DxeCpuExceptionHandlerLib.inf
>> MpInitLib|UefiCpuPkg/Library/MpInitLib/DxeMpInitLib.inf
>>
>> RegisterCpuFeaturesLib|UefiCpuPkg/Library/RegisterCpuFeaturesLib/DxeRegisterCpuFeaturesLib.inf
>> + VmgExitLib|UefiCpuPkg/Library/VmgExitLib/VmgExitLib.inf
>>
>> [LibraryClasses.common.DXE_SMM_DRIVER]
>>
>> SmmServicesTableLib|MdePkg/Library/SmmServicesTableLib/SmmServicesTableLib.inf
>>
>> MemoryAllocationLib|MdePkg/Library/SmmMemoryAllocationLib/SmmMemoryAllocationLib.inf
>> HobLib|MdePkg/Library/DxeHobLib/DxeHobLib.inf
>>
>> CpuExceptionHandlerLib|UefiCpuPkg/Library/CpuExceptionHandlerLib/SmmCpuExceptionHandlerLib.inf
>> + VmgExitLib|UefiCpuPkg/Library/VmgExitLib/VmgExitLib.inf
>>
>> [LibraryClasses.common.UEFI_APPLICATION]
>>
>> UefiApplicationEntryPoint|MdePkg/Library/UefiApplicationEntryPoint/UefiApplicationEntryPoint.inf
>> @@ -136,6 +140,7 @@ [Components.IA32, Components.X64]
>> UefiCpuPkg/Library/SmmCpuPlatformHookLibNull/SmmCpuPlatformHookLibNull.inf
>> UefiCpuPkg/Library/SmmCpuFeaturesLib/SmmCpuFeaturesLib.inf
>> UefiCpuPkg/Library/SmmCpuFeaturesLib/SmmCpuFeaturesLibStm.inf
>> + UefiCpuPkg/Library/VmgExitLib/VmgExitLib.inf
>> UefiCpuPkg/PiSmmCommunication/PiSmmCommunicationPei.inf
>> UefiCpuPkg/PiSmmCommunication/PiSmmCommunicationSmm.inf
>> UefiCpuPkg/SecCore/SecCore.inf
>> diff --git a/UefiCpuPkg/Library/VmgExitLib/VmgExitLib.inf
>> b/UefiCpuPkg/Library/VmgExitLib/VmgExitLib.inf
>> new file mode 100644
>> index 000000000000..6acfa779e75a
>> --- /dev/null
>> +++ b/UefiCpuPkg/Library/VmgExitLib/VmgExitLib.inf
>> @@ -0,0 +1,33 @@
>> +## @file
>> +# VMGEXIT Support Library.
>> +#
>> +# Copyright (c) 2019, Advanced Micro Devices, Inc. All rights reserved.<BR>
>> +# SPDX-License-Identifier: BSD-2-Clause-Patent
>> +#
>> +##
>> +
>> +[Defines]
>> + INF_VERSION = 0x00010005
>> + BASE_NAME = VmgExitLib
>> + MODULE_UNI_FILE = VmgExitLib.uni
>> + FILE_GUID = 3cd7368f-ef9b-4a9b-9571-2ed93813677e
>> + 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 = IA32 X64
>> +#
>> +
>> +[Sources]
>> + VmgExitLib.c
>> +
>> +[Packages]
>> + MdePkg/MdePkg.dec
>> + UefiCpuPkg/UefiCpuPkg.dec
>> +
>> +[LibraryClasses]
>> + BaseLib
>> +
>> diff --git a/UefiCpuPkg/Include/Library/VmgExitLib.h
>> b/UefiCpuPkg/Include/Library/VmgExitLib.h
>> new file mode 100644
>> index 000000000000..b5639fbfa1a5
>> --- /dev/null
>> +++ b/UefiCpuPkg/Include/Library/VmgExitLib.h
>> @@ -0,0 +1,96 @@
>> +/** @file
>> + Public header file for the VMGEXIT Support library class.
>> +
>> + This library class defines some routines used when invoking the VMGEXIT
>> + instruction in support of SEV-ES.
>> +
>> + Copyright (c) 2019, Advanced Micro Devices, Inc. All rights reserved.<BR>
>> + SPDX-License-Identifier: BSD-2-Clause-Patent
>> +
>> +**/
>> +
>> +#ifndef __VMG_EXIT_LIB_H__
>> +#define __VMG_EXIT_LIB_H__
>> +
>> +#include <Register/Amd/Ghcb.h>
>> +
>> +
>> +/**
>> + Perform VMGEXIT.
>> +
>> + Sets the necessary fields of the GHCB, invokes the VMGEXIT instruction and
>> + then handles the return actions.
>> +
>> + @param[in] 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.
>> + @retval Others VMGEXIT processing did not succeed. Exception number to
>> + be issued.
>> +
>> +**/
>> +UINTN
>> +EFIAPI
>> +VmgExit (
>> + GHCB *Ghcb,
>> + UINT64 ExitCode,
>> + UINT64 ExitInfo1,
>> + UINT64 ExitInfo2
>> + );
>> +
>> +/**
>> + Perform pre-VMGEXIT initialization/preparation.
>> +
>> + Performs the necessary steps in preparation for invoking VMGEXIT.
>> +
>> + @param[in] GHCB A pointer to the GHCB
>> +
>> +**/
>> +VOID
>> +EFIAPI
>> +VmgInit (
>> + GHCB *Ghcb
>> + );
>> +
>> +/**
>> + Perform post-VMGEXIT cleanup.
>> +
>> + Performs the necessary steps to cleanup after invoking VMGEXIT.
>> +
>> + @param[in] GHCB A pointer to the GHCB
>> +
>> +**/
>> +VOID
>> +EFIAPI
>> +VmgDone (
>> + GHCB *Ghcb
>> + );
>> +
>> +#define VMGMMIO_READ False
>> +#define VMGMMIO_WRITE True
>> +
>> +/**
>> + Perform MMIO write of a buffer to a non-MMIO marked range.
>> +
>> + Performs an MMIO write without taking a #VC. This is useful
>> + for Flash devices, which are marked read-only.
>> +
>> + @param[in] UINT8 A pointer to the destination buffer
>> + @param[in] UINTN The immediate value to write
>> + @param[in] UINTN Number of bytes to write
>> +
>> +**/
>> +VOID
>> +EFIAPI
>> +VmgMmioWrite (
>> + UINT8 *Dest,
>> + UINT8 *Src,
>> + UINTN Bytes
>> + );
>> +
>> +#endif
>> diff --git a/UefiCpuPkg/Library/VmgExitLib/VmgExitLib.c
>> b/UefiCpuPkg/Library/VmgExitLib/VmgExitLib.c
>> new file mode 100644
>> index 000000000000..23965b7ff022
>> --- /dev/null
>> +++ b/UefiCpuPkg/Library/VmgExitLib/VmgExitLib.c
>> @@ -0,0 +1,132 @@
>> +/** @file
>> + VMGEXIT Support Library.
>> +
>> + Copyright (c) 2019, 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 <Register/Amd/Ghcb.h>
>> +#include <Register/Amd/Msr.h>
>> +
>> +STATIC
>> +UINTN
>> +VmgExitErrorCheck (
>> + GHCB *Ghcb
>> + )
>> +{
>> + GHCB_EXIT_INFO ExitInfo;
>> + UINTN Reason, Action;
>> +
>> + if (!Ghcb->SaveArea.SwExitInfo1) {
>> + return 0;
>> + }
>> +
>> + ExitInfo.Uint64 = Ghcb->SaveArea.SwExitInfo1;
>> + Action = ExitInfo.Elements.Lower32Bits;
>> + if (Action == 1) {
>> + Reason = ExitInfo.Elements.Upper32Bits;
>> +
>> + switch (Reason) {
>> + case UD_EXCEPTION:
>> + case GP_EXCEPTION:
>> + return Reason;
>> + }
>> + }
>> +
>> + ASSERT (0);
>> + return GP_EXCEPTION;
>> +}
>> +
>> +UINTN
>> +EFIAPI
>> +VmgExit (
>> + GHCB *Ghcb,
>> + UINT64 ExitCode,
>> + UINT64 ExitInfo1,
>> + UINT64 ExitInfo2
>> + )
>> +{
>> + Ghcb->SaveArea.SwExitCode = ExitCode;
>> + Ghcb->SaveArea.SwExitInfo1 = ExitInfo1;
>> + Ghcb->SaveArea.SwExitInfo2 = ExitInfo2;
>> + AsmVmgExit ();
>
> This patch looks good to me (and, in general, I'd like to defer to Ray
> and Eric on the UefiCpuPkg patches); just one comment:
>
> AsmVmgExit() orchestrates guest-host communication in guest RAM, and in
> that sense, it is somewhat similar to virtio. In virtio (per spec), we
> use MemoryFence() calls carefully.
>
> Now, if you check the MemoryFence() implementation in
> "MdePkg/Library/BaseLib/X64/GccInline.c", it is only
>
> __asm__ __volatile__ ("":::"memory");
>
> which is already part of AsmVmgExit(), from the previous patch:
>
> [edk2-devel] [RFC PATCH v3 06/43]
> MdePkg/BaseLib: Add support for the VMGEXIT instruction
>
> __asm__ __volatile__ ("rep; vmmcall":::"memory");
>
> So, I think it's not necessary *in practice* to add a MemoryFence()
> ahead of the AsmVmgExit(). But, I think it is needed afterwards.
>
> The comment in "MdePkg/Library/BaseLib/X64/GccInline.c" says, "it is
> more about the compiler that it is actually processor synchronization".
> With that in mind, I'd like to suggest one of two alternatives:
>
> - modify the AsmVmgExit() documentation (function level comment in the
> lib class header) so that it spell out that all barriers (before &
> after) are contained within,
>
> - or please modify the call site so that it is both preceded and
> succeeded by MemoryFence().
I'll update VmgExit() in VmgExitLib.c to add the MemoryFence() calls
around the invocation of AsmVmgExit().
Thanks,
Tom
>
> With either option implemented:
>
> Acked-by: Laszlo Ersek <ler...@redhat.com>
>
> Thanks
> Laszlo
>
>
>
>> +
>> + return VmgExitErrorCheck (Ghcb);
>> +}
>> +
>> +VOID
>> +EFIAPI
>> +VmgInit (
>> + GHCB *Ghcb
>> + )
>> +{
>> + SetMem (&Ghcb->SaveArea, sizeof (Ghcb->SaveArea), 0);
>> +}
>> +
>> +VOID
>> +EFIAPI
>> +VmgDone (
>> + GHCB *Ghcb
>> + )
>> +{
>> +}
>> +
>> +UINTN
>> +EFIAPI
>> +VmgMmio (
>> + UINT8 *MmioAddress,
>> + UINT8 *Buffer,
>> + UINTN Bytes,
>> + BOOLEAN Write
>> + )
>> +{
>> + UINT64 MmioOp;
>> + UINT64 ExitInfo1, ExitInfo2;
>> + UINTN Status;
>> + GHCB *Ghcb;
>> + MSR_SEV_ES_GHCB_REGISTER Msr;
>> +
>> + Msr.GhcbPhysicalAddress = AsmReadMsr64 (MSR_SEV_ES_GHCB);
>> + Ghcb = Msr.Ghcb;
>> +
>> + if (Write) {
>> + MmioOp = SvmExitMmioWrite;
>> + } else {
>> + MmioOp = SvmExitMmioRead;
>> + }
>> +
>> + ExitInfo1 = (UINT64) (UINTN) MmioAddress;
>> + ExitInfo2 = Bytes;
>> +
>> + if (Write) {
>> + CopyMem (Ghcb->SharedBuffer, Buffer, Bytes);
>> + }
>> +
>> + Ghcb->SaveArea.SwScratch = (UINT64) (UINTN) Ghcb->SharedBuffer;
>> + Status = VmgExit (Ghcb, MmioOp, ExitInfo1, ExitInfo2);
>> + if (Status != 0) {
>> + return Status;
>> + }
>> +
>> + if (!Write) {
>> + CopyMem (Buffer, Ghcb->SharedBuffer, Bytes);
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +VOID
>> +EFIAPI
>> +VmgMmioWrite (
>> + UINT8 *Dest,
>> + UINT8 *Src,
>> + UINTN Bytes
>> + )
>> +{
>> + VmgMmio (Dest, Src, Bytes, TRUE);
>> +}
>> +
>> diff --git a/UefiCpuPkg/Library/VmgExitLib/VmgExitLib.uni
>> b/UefiCpuPkg/Library/VmgExitLib/VmgExitLib.uni
>> new file mode 100644
>> index 000000000000..e8656aae4726
>> --- /dev/null
>> +++ b/UefiCpuPkg/Library/VmgExitLib/VmgExitLib.uni
>> @@ -0,0 +1,15 @@
>> +// /** @file
>> +// VMGEXIT support library instance.
>> +//
>> +// VMGEXIT support library instance.
>> +//
>> +// Copyright (c) 2019, Advanced Micro Devices, Inc. All rights reserved.<BR>
>> +// SPDX-License-Identifier: BSD-2-Clause-Patent
>> +//
>> +// **/
>> +
>> +
>> +#string STR_MODULE_ABSTRACT #language en-US "VMGEXIT Support
>> Library."
>> +
>> +#string STR_MODULE_DESCRIPTION #language en-US "VMGEXIT Support
>> Library."
>> +
>>
>
>
>
>
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