[edk2-devel] [RFC PATCH 00/19] Add AMD Secure Nested Paging (SEV-SNP) support
Laszlo Ersek
lersek at redhat.com
Thu Apr 8 09:58:10 UTC 2021
Hi Brijesh,
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.
>
> 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.
Can you describe this in a bit more detail, before I look at the
individual patches? Specifically, what existing logic in the PEI phase
was taken, and extended, and how?
If there is a particular patch whose commit message is closely related
to my question, can you point it out? Patch#15 perhaps? (Doesn't seem
like a big patch; for some reason I'd expect something more complex, but
perhaps that's only because it builds upon the many earlier patches.)
Thanks,
Laszlo
>
> 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 at linux.ibm.com>
> Cc: Min Xu <min.m.xu at intel.com>
> Cc: Jiewen Yao <jiewen.yao at intel.com>
> Cc: Tom Lendacky <thomas.lendacky at amd.com>
> Cc: Jordan Justen <jordan.l.justen at intel.com>
> Cc: Ard Biesheuvel <ardb+tianocore at kernel.org>
> Cc: Laszlo Ersek <lersek at 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
>
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