Re: [edk2-devel] [RFC PATCH 00/19] Add AMD Secure Nested Paging (SEV-SNP) support

["Laszlo Ersek" <lersek@redhat.com>]

On 03/24/21 16:31, Brijesh Singh wrote:
> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3275
> 
> SEV-SNP builds upon existing SEV and SEV-ES functionality while adding
> new hardware-based memory protections. SEV-SNP adds strong memory integrity
> protection to help prevent malicious hypervisor-based attacks like data
> replay, memory re-mapping and more in order to create an isolated memory
> encryption environment.
>  
> This series provides the basic building blocks to support booting the SEV-SNP
> VMs, it does not cover all the security enhancement introduced by the SEV-SNP
> such as interrupt protection.

Thanks, Brijesh. I'm adding the series to my review queue. Due to some
PTO coming up, I'll probably start reviewing this work only in April.
Other reviewers, please feel free to have at it.

Cheers
Laszlo

> 
> Many of the integrity guarantees of SEV-SNP are enforced through a new
> structure called the Reverse Map Table (RMP). Adding a new page to SEV-SNP
> VM requires a 2-step process. First, the hypervisor assigns a page to the
> guest using the new RMPUPDATE instruction. This transitions the page to
> guest-invalid. Second, the guest validates the page using the new PVALIDATE
> instruction. The SEV-SNP VMs can use the new "Page State Change Request NAE"
> defined in the GHCB specification to ask hypervisor to add or remove page
> from the RMP table.
>  
> Each page assigned to the SEV-SNP VM can either be validated or unvalidated,
> as indicated by the Validated flag in the page's RMP entry. There are two
> approaches that can be taken for the page validation: Pre-validation and
> Lazy Validation.
>   
> Under pre-validation, the pages are validated prior to first use. And under
> lazy validation, pages are validated when first accessed. An access to a
> unvalidated page results in a #VC exception, at which time the exception
> handler may validate the page. Lazy validation requires careful tracking of
> the validated pages to avoid validating the same GPA more than once. The
> recently introduced "Unaccepted" memory type can be used to communicate the
> unvalidated memory ranges to the Guest OS.
> 
> At this time we only support the pre-validation. OVMF detects all the available
> system RAM in the PEI phase. When SEV-SNP is enabled, the memory is validated
> before it is made available to the EDK2 core.
> 
> This series does not implements the following SEV-SNP features yet:
> 
> * CPUID filtering
> * AP bring up using the new SEV-SNP NAE
> * Lazy validation
> * Interrupt security
> 
> The series is based on commit:
> e542e05d4f UefiCpuPkg/SmmCpuFeaturesLib: Abstract PcdCpuMaxLogicalProcessorNumber
> 
> Additional resources
> ---------------------
> SEV-SNP whitepaper
> https://www.amd.com/system/files/TechDocs/SEV-SNP-strengthening-vm-isolation-with-integrity-protection-and-more.pdf
>  
> APM 2: https://www.amd.com/system/files/TechDocs/24593.pdf (section 15.36)
> 
> The complete source is available at
> https://github.com/AMDESE/ovmf/tree/sev-snp-rfc-1
> 
> GHCB spec v2:
>   The draft specification is posted on AMD-SEV-SNP mailing list:
>    https://lists.suse.com/mailman/private/amd-sev-snp/
> 
>   Copy of the spec is also available at 
>   https://github.com/AMDESE/AMDSEV/blob/sev-snp-devel/docs/56421-Guest_Hypervisor_Communication_Block_Standardization.pdf
> 
> GHCB spec v1:
> SEV-SNP firmware specification:
>  https://developer.amd.com/sev/
>   
> Cc: James Bottomley <jejb@linux.ibm.com>
> Cc: Min Xu <min.m.xu@intel.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> Cc: Laszlo Ersek <lersek@redhat.com>
> 
> Brijesh Singh (19):
>   OvmfPkg: Reserve the Secrets and Cpuid page for the SEV-SNP guest
>   OvmfPkg: validate the data pages used in the SEC phase
>   MdePkg: Expand the SEV MSR to include the SNP definition
>   OvmfPkg/MemEncryptSevLib: add MemEncryptSevSnpEnabled()
>   MdePkg: Define the GHCB GPA structure
>   UefiCpuPkg/MpLib: add support to register GHCB GPA when SEV-SNP is
>     enabled
>   OvmfPkg: Add a library to support registering GHCB GPA
>   OvmfPkg: register GHCB gpa for the SEV-SNP guest
>   MdePkg: Add AsmPvalidate() support
>   OvmfPkg: Define the Page State Change VMGEXIT structures
>   OvmfPkg/ResetVector: Invalidate the GHCB page
>   OvmfPkg/MemEncryptSevLib: Add support to validate system RAM
>   OvmfPkg/SecMain: Validate the data/code pages used for the PEI phase
>   OvmfPkg/MemEncryptSevLib: Add support to validate RAM in PEI phase
>   OvmfPkg/PlatformPei: Validate the system RAM when SNP is active
>   OvmfPkg/MemEncryptSevLib: Add support to validate > 4GB memory in PEI
>     phase
>   OvmfPkg/VmgExitLib: Allow PMBASE register access in Dxe phase
>   OvmfPkg/MemEncryptSevLib: Validate the memory during set or clear enc
>     attribute
>   OvmfPkg/MemEncryptSevLib: Skip page state change for non RAM region
> 
>  MdePkg/Include/Library/BaseLib.h              |  37 +++
>  MdePkg/Include/Register/Amd/Fam17Msr.h        |  31 ++-
>  MdePkg/Include/Register/Amd/Ghcb.h            |  39 ++-
>  MdePkg/Library/BaseLib/BaseLib.inf            |   1 +
>  MdePkg/Library/BaseLib/X64/Pvalidate.nasm     |  43 +++
>  OvmfPkg/Include/Library/GhcbRegisterLib.h     |  27 ++
>  OvmfPkg/Include/Library/MemEncryptSevLib.h    |  30 +++
>  .../DxeMemEncryptSevLib.inf                   |   7 +
>  .../DxeMemEncryptSevLibInternal.c             |  27 ++
>  .../Ia32/SnpPageStateChange.c                 |  17 ++
>  .../PeiMemEncryptSevLib.inf                   |   9 +
>  .../PeiMemEncryptSevLibInternal.c             |  47 ++++
>  .../SecMemEncryptSevLib.inf                   |   4 +
>  .../SecMemEncryptSevLibInternal.c             |  39 +++
>  .../BaseMemEncryptSevLib/SnpPageStateChange.h |  37 +++
>  .../X64/PeiDxeSnpSetPageState.c               |  63 +++++
>  .../X64/PeiDxeVirtualMemory.c                 | 151 ++++++++++-
>  .../X64/PeiSnpSystemRamValidate.c             | 129 +++++++++
>  .../X64/SecSnpSystemRamValidate.c             |  23 ++
>  .../X64/SnpPageStateChangeInternal.c          | 254 ++++++++++++++++++
>  .../X64/SnpPageStateTrack.c                   | 119 ++++++++
>  .../X64/SnpPageStateTrack.h                   |  36 +++
>  .../X64/SnpSetPageState.h                     |  27 ++
>  .../BaseMemEncryptSevLib/X64/VirtualMemory.h  |  19 ++
>  .../Library/GhcbRegisterLib/GhcbRegisterLib.c |  97 +++++++
>  .../GhcbRegisterLib/GhcbRegisterLib.inf       |  33 +++
>  OvmfPkg/Library/VmgExitLib/SecVmgExitLib.inf  |   4 +
>  OvmfPkg/Library/VmgExitLib/VmgExitLib.inf     |   7 +
>  OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c |  45 ++++
>  OvmfPkg/OvmfPkg.dec                           |  12 +
>  OvmfPkg/OvmfPkgX64.dsc                        |   1 +
>  OvmfPkg/OvmfPkgX64.fdf                        |  33 ++-
>  OvmfPkg/PlatformPei/AmdSev.c                  |  52 ++++
>  OvmfPkg/PlatformPei/PlatformPei.inf           |   2 +
>  OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm  |  24 ++
>  OvmfPkg/ResetVector/Ia32/PageTables64.asm     | 106 ++++++++
>  OvmfPkg/ResetVector/ResetVector.inf           |   5 +
>  OvmfPkg/ResetVector/ResetVector.nasmb         |   4 +
>  OvmfPkg/Sec/SecMain.c                         | 102 +++++++
>  OvmfPkg/Sec/SecMain.inf                       |   2 +
>  UefiCpuPkg/Library/MpInitLib/DxeMpInitLib.inf |   1 +
>  UefiCpuPkg/Library/MpInitLib/MpEqu.inc        |   1 +
>  UefiCpuPkg/Library/MpInitLib/MpLib.c          |   2 +
>  UefiCpuPkg/Library/MpInitLib/MpLib.h          |   2 +
>  UefiCpuPkg/Library/MpInitLib/PeiMpInitLib.inf |   1 +
>  UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm |  51 ++++
>  UefiCpuPkg/UefiCpuPkg.dec                     |   6 +
>  47 files changed, 1790 insertions(+), 19 deletions(-)
>  create mode 100644 MdePkg/Library/BaseLib/X64/Pvalidate.nasm
>  create mode 100644 OvmfPkg/Include/Library/GhcbRegisterLib.h
>  create mode 100644 OvmfPkg/Library/BaseMemEncryptSevLib/Ia32/SnpPageStateChange.c
>  create mode 100644 OvmfPkg/Library/BaseMemEncryptSevLib/SnpPageStateChange.h
>  create mode 100644 OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiDxeSnpSetPageState.c
>  create mode 100644 OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiSnpSystemRamValidate.c
>  create mode 100644 OvmfPkg/Library/BaseMemEncryptSevLib/X64/SecSnpSystemRamValidate.c
>  create mode 100644 OvmfPkg/Library/BaseMemEncryptSevLib/X64/SnpPageStateChangeInternal.c
>  create mode 100644 OvmfPkg/Library/BaseMemEncryptSevLib/X64/SnpPageStateTrack.c
>  create mode 100644 OvmfPkg/Library/BaseMemEncryptSevLib/X64/SnpPageStateTrack.h
>  create mode 100644 OvmfPkg/Library/BaseMemEncryptSevLib/X64/SnpSetPageState.h
>  create mode 100644 OvmfPkg/Library/GhcbRegisterLib/GhcbRegisterLib.c
>  create mode 100644 OvmfPkg/Library/GhcbRegisterLib/GhcbRegisterLib.inf
>