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

["Yao, Jiewen" <jiewen.yao@intel.com>]

Thanks Tom. Below is exactly what I am looking for:
"the decision to use the SVSM API will be based on the VMPL level at which OVMF is running."

OVMF needs to detect SEV-SNP, then make next level decision on VMPL.
Makes sense to me.

Thank you
Yao, Jiewen

> -----Original Message-----
> From: Tom Lendacky <thomas.lendacky@amd.com>
> Sent: Sunday, January 28, 2024 1:49 AM
> To: Yao, Jiewen <jiewen.yao@intel.com>; devel@edk2.groups.io
> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>; Aktas, Erdem
> <erdemaktas@google.com>; Gerd Hoffmann <kraxel@redhat.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: Re: [PATCH 00/16] Provide SEV-SNP support for running under an SVSM
> 
> 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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