Re: [edk2-devel] [PATCH 00/16] Provide SEV-SNP support for running under an SVSM

["Lendacky, Thomas via groups.io" <thomas.lendacky=amd.com@groups.io>]

On 1/26/24 22:04, Yao, Jiewen wrote:
> Thanks Tom.
> Please give me some time to digest this patch set before I can give some feedback.
> 
> One quick question to you:
> With this patch, we need to support multiple SEV modes:
> 1. SEV guest firmware
> 2. SEV-ES guest firmware
> 3. SEV-SNP guest firmware
> 4. SEV-SNP SVSM guest firmware

This last mode is still an SNP guest, it just requires invoking an API to 
perform operations that require VMPL0 permissions. I'm not sure what you 
mean by having firmware at the end of each mode. The same firmware is used 
for all SEV guest modes as well as non-SEV guests.

> And all these mode requires runtime detection. Am I right?

Yes

> If so, where is the flag to set those mode?

There are function calls available to detect the SEV mode. See the 
implementation of MemEncryptSevIsEnabled(), MemEncryptSevEsIsEnabled() and 
MemEncryptSevSnpIsEnabled().

OvmfPkg/Library/BaseMemEncryptSevLib/SecMemEncryptSevLibInternal.c
OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLibInternal.c
OvmfPkg/Library/BaseMemEncryptSevLib/DxeMemEncryptSevLibInternal.c

(OvmfPkg/Sec/AmdSev.c also has some early detection support)

Note:
   - An SEV-SNP guest is also considered an SEV-ES and SEV guest.
   - An SEV-ES guest is also considered an SEV guest.

Within the CcExitLib library, the decision to use the SVSM API will be 
based on the VMPL level at which OVMF is running.

Thanks,
Tom

> 
> Please correct me if my understanding is wrong.
> 
> Thank you
> Yao, Jiewen
> 
>> -----Original Message-----
>> From: Tom Lendacky <thomas.lendacky@amd.com>
>> Sent: Saturday, January 27, 2024 6:13 AM
>> To: devel@edk2.groups.io
>> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>; Aktas, Erdem
>> <erdemaktas@google.com>; Gerd Hoffmann <kraxel@redhat.com>; Yao, Jiewen
>> <jiewen.yao@intel.com>; Laszlo Ersek <lersek@redhat.com>; Liming Gao
>> <gaoliming@byosoft.com.cn>; Kinney, Michael D <michael.d.kinney@intel.com>;
>> Xu, Min M <min.m.xu@intel.com>; Liu, Zhiguang <zhiguang.liu@intel.com>;
>> Kumar, Rahul R <rahul.r.kumar@intel.com>; Ni, Ray <ray.ni@intel.com>; Michael
>> Roth <michael.roth@amd.com>
>> Subject: [PATCH 00/16] Provide SEV-SNP support for running under an SVSM
>>
>>
>> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=4654
>>
>> This series adds SEV-SNP support for running OVMF under an Secure VM
>> Service Module (SVSM) at a less privileged VM Privilege Level (VMPL).
>> By running at a less priviledged VMPL, the SVSM can be used to provide
>> services, e.g. a virtual TPM, for the guest OS within the SEV-SNP
>> confidential VM (CVM) rather than trust such services from the hypervisor.
>>
>> Currently, OVMF expects to run at the highest VMPL, VMPL0, and there are
>> certain SNP related operations that require that VMPL level. Specifically,
>> the PVALIDATE instruction and the RMPADJUST instruction when setting the
>> the VMSA attribute of a page (used when starting APs).
>>
>> If OVMF is to run at a less privileged VMPL, e.g. VMPL2, then it must
>> use an SVSM (which is running at VMPL0) to perform the operations that
>> it is no longer able to perform.
>>
>> How OVMF interacts with and uses the SVSM is documented in the SVSM
>> specification [1] and the GHCB specification [2].
>>
>> This series introduces support to run OVMF under an SVSM. It consists
>> of:
>>    - Reorganize the page state change support to not directly use the
>>      GHCB buffer since an SVSM will use the calling area buffer, instead
>>    - Detecting the presence of an SVSM
>>    - When not running at VMPL0, invoking the SVSM for page validation and
>>      VMSA page creation/deletion
>>    - Retrieving the list of vCPU APIC IDs and starting up all APs without
>>      performing a broadcast SIPI
>>    - Detecting and allowing OVMF to run in a VMPL other than 0 when an
>>      SVSM is present
>>
>> The series is based off of commit:
>>
>>    7d7decfa3dc8 ("UefiPayloadPkg/Crypto: Support external Crypto drivers.")
>>
>> [1] https://www.amd.com/content/dam/amd/en/documents/epyc-technical-
>> docs/specifications/58019.pdf
>> [2] https://www.amd.com/content/dam/amd/en/documents/epyc-technical-
>> docs/specifications/56421.pdf
>>
>> ---
>>
>> Tom Lendacky (16):
>>    OvmfPkg/BaseMemEncryptSevLib: Re-organize page state change support
>>    MdePkg/Register/Amd: Define the SVSM related information
>>    MdePkg/BaseLib: Add a new VMGEXIT instruction invocation for SVSM
>>    UefiCpuPkg/CcExitLib: Extend the CcExitLib library to support an SVSM
>>    Ovmfpkg/CcExitLib: Extend CcExitLib to handle SVSM related services
>>    OvmfPkg: Create a calling area used to communicate with the SVSM
>>    OvmfPkg/CcExitLib: Add support for the SVSM_CORE_PVALIDATE call
>>    OvmfPkg/CcExitLib: Add support for the SVSM create/delete vCPU calls
>>    UefiCpuPkg/MpInitLib: Use CcExitSnpVmsaRmpAdjust() to set/clear VMSA
>>    MdePkg: GHCB APIC ID retrieval support definitions
>>    UefiCpuPkg: Create APIC ID list PCD
>>    OvmfPkg/PlatformPei: Retrieve APIC IDs from the hypervisor
>>    UefiCpuPkg/MpInitLib: Always use AP Create if PcdSevSnpApicIds is set
>>    UefiCpuPkg/MpInitLib: AP creation support under an SVSM
>>    Ovmfpkg/CcExitLib: Provide SVSM discovery support
>>    OvmfPkg/BaseMemEncryptLib: Check for presence of an SVSM when not at
>>      VMPL0
>>
>>   OvmfPkg/OvmfPkg.dec                                                   |   4 +
>>   UefiCpuPkg/UefiCpuPkg.dec                                             |   7 +-
>>   OvmfPkg/AmdSev/AmdSevX64.fdf                                          |   9 +-
>>   OvmfPkg/OvmfPkgX64.fdf                                                |   3 +
>>   MdePkg/Library/BaseLib/BaseLib.inf                                    |   2 +
>>   OvmfPkg/Library/CcExitLib/CcExitLib.inf                               |   5 +-
>>   OvmfPkg/Library/CcExitLib/SecCcExitLib.inf                            |   5 +-
>>   OvmfPkg/PlatformPei/PlatformPei.inf                                   |   3 +
>>   OvmfPkg/ResetVector/ResetVector.inf                                   |   2 +
>>   UefiCpuPkg/Library/MpInitLib/DxeMpInitLib.inf                         |   1 +
>>   UefiCpuPkg/Library/MpInitLib/PeiMpInitLib.inf                         |   3 +-
>>   MdePkg/Include/Library/BaseLib.h                                      |  39 ++
>>   MdePkg/Include/Register/Amd/Fam17Msr.h                                |  19 +-
>>   MdePkg/Include/Register/Amd/Ghcb.h                                    |  19 +-
>>   MdePkg/Include/Register/Amd/Msr.h                                     |   3 +-
>>   MdePkg/Include/Register/Amd/Svsm.h                                    | 101 ++++
>>   MdePkg/Include/Register/Amd/SvsmMsr.h                                 |  35 ++
>>   OvmfPkg/Include/WorkArea.h                                            |   7 +
>>   OvmfPkg/Library/BaseMemEncryptSevLib/X64/SnpPageStateChange.h         |   4
>> +-
>>   OvmfPkg/Library/CcExitLib/CcExitSvsm.h                                |  29 ++
>>   UefiCpuPkg/Include/Library/CcExitLib.h                                |  71 ++-
>>   UefiCpuPkg/Library/MpInitLib/MpLib.h                                  |  27 +-
>>   OvmfPkg/Library/BaseMemEncryptSevLib/X64/DxeSnpSystemRamValidate.c    |
>> 16 +-
>>   OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiDxeVirtualMemory.c        |  25
>> +-
>>   OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiSnpSystemRamValidate.c    |
>> 20 +-
>>   OvmfPkg/Library/BaseMemEncryptSevLib/X64/SecSnpSystemRamValidate.c    |
>> 25 +-
>>   OvmfPkg/Library/BaseMemEncryptSevLib/X64/SnpPageStateChangeInternal.c |
>> 203 ++++----
>>   OvmfPkg/Library/CcExitLib/CcExitSvsm.c                                | 532
>> ++++++++++++++++++++
>>   OvmfPkg/Library/CcExitLib/CcExitVcHandler.c                           |  29 +-
>>   OvmfPkg/PlatformPei/AmdSev.c                                          | 100 +++-
>>   UefiCpuPkg/Library/CcExitLibNull/CcExitLibNull.c                      |  82 ++-
>>   UefiCpuPkg/Library/MpInitLib/Ia32/AmdSev.c                            |  19 +-
>>   UefiCpuPkg/Library/MpInitLib/MpLib.c                                  |   7 +-
>>   UefiCpuPkg/Library/MpInitLib/X64/AmdSev.c                             | 127 +++--
>>   MdePkg/Library/BaseLib/Ia32/VmgExitSvsm.nasm                          |  39 ++
>>   MdePkg/Library/BaseLib/X64/VmgExitSvsm.nasm                           |  94 ++++
>>   OvmfPkg/ResetVector/ResetVector.nasmb                                 |   6 +-
>>   OvmfPkg/ResetVector/X64/OvmfSevMetadata.asm                           |   9 +
>>   UefiCpuPkg/UefiCpuPkg.uni                                             |   3 +
>>   39 files changed, 1524 insertions(+), 210 deletions(-)
>>   create mode 100644 MdePkg/Include/Register/Amd/Svsm.h
>>   create mode 100644 MdePkg/Include/Register/Amd/SvsmMsr.h
>>   create mode 100644 OvmfPkg/Library/CcExitLib/CcExitSvsm.h
>>   create mode 100644 OvmfPkg/Library/CcExitLib/CcExitSvsm.c
>>   create mode 100644 MdePkg/Library/BaseLib/Ia32/VmgExitSvsm.nasm
>>   create mode 100644 MdePkg/Library/BaseLib/X64/VmgExitSvsm.nasm
>>
>> --
>> 2.42.0
> 


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