[PATCH v7 00/31] Add AMD Secure Nested Paging (SEV-SNP) support

Brijesh Singh

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.

Now that series contains all the basic support required to launch SEV-SNP
guest. We are still missing the Interrupt security feature provided by the
SNP. The feature will be added after the base support is accepted.

Additional resources
SEV-SNP whitepaper

APM 2: https://www.amd.com/system/files/TechDocs/24593.pdf (section 15.36)

The complete source is available at

GHCB spec:

SEV-SNP firmware specification:

Change since v6:
* Drop the SNP boot block GUID and switch to using the Metadata guided structure
proposed by Min in TDX series.
* Exclude the GHCB page from the pre-validated region. It simplifies the reset
vector code where we do not need to unvalidate the GHCB page.
* Now that GHCB page is not validated so move the VMPL check from reset vector
code to the MemEncryptSevLib on the first page validation.
* Introduce the ConfidentialComputingGuestAttr PCD to communicate which
memory encryption is active so that MpInitLib can make use of it.
* Drop the SEVES specific PCD as the information can be communicated via
the ConfidentialComputingGuestAttr.
* Move the SNP specific AP creation function in AmdSev.c.
* Define the SNP Blob GUID in a new file.

Change since v5:
* When possible use the CPUID value from CPUID page
* Move the SEV specific functions from SecMain.c in AmdSev.c
* Rebase to the latest code
* Add the review feedback from Yao.

Change since v4:
* Use the correct MSR for the SEV_STATUS
* Add VMPL-0 check

Change since v3:
* ResetVector: move all SEV specific code in AmdSev.asm and add macros to keep
the code readable.
* Drop extending the EsWorkArea to contain SNP specific state.
* Drop the GhcbGpa library and call the VmgExit directly to register GHCB GPA.
* Install the CC blob config table from AmdSevDxe instead of extending the
AmdSev/SecretsDxe for it.
* Add the separate PCDs for the SNP Secrets.

Changes since v2:
* Add support for the AP creation.
* Use the module-scoping override to make AmdSevDxe use the IO port for PCI reads.
* Use the reserved memory type for CPUID and Secrets page.
Changes since v1:
* Drop the interval tree support to detect the pre-validated overlap region.
* Use an array to keep track of pre-validated regions.
* Add support to query the Hypervisor feature and verify that SNP feature is supported.
* Introduce MemEncryptSevClearMmioPageEncMask() to clear the C-bit from MMIO ranges.
* Pull the SevSecretDxe and SevSecretPei into OVMF package build.
* Extend the SevSecretDxe to expose confidential computing blob location through
EFI configuration table.

Brijesh Singh (27):
OvmfPkg/SecMain: move SEV specific routines in AmdSev.c
OvmfPkg/ResetVector: move clearing GHCB in SecMain
OvmfPkg/ResetVector: introduce metadata descriptor for VMM use
OvmfPkg: reserve SNP secrets page
OvmfPkg: reserve CPUID page
OvmfPkg/ResetVector: pre-validate the data pages used in SEC phase
OvmfPkg/MemEncryptSevLib: add MemEncryptSevSnpEnabled()
OvmfPkg/SecMain: register GHCB gpa for the SEV-SNP guest
OvmfPkg/PlatformPei: register GHCB gpa for the SEV-SNP guest
OvmfPkg/AmdSevDxe: do not use extended PCI config space
OvmfPkg/MemEncryptSevLib: add support to validate system RAM
OvmfPkg/MemEncryptSevLib: add function to check the VMPL0
OvmfPkg/BaseMemEncryptSevLib: skip the pre-validated system RAM
OvmfPkg/MemEncryptSevLib: add support to validate > 4GB memory in PEI
OvmfPkg/SecMain: pre-validate the memory used for decompressing Fv
OvmfPkg/PlatformPei: validate the system RAM when SNP is active
UefiCpuPkg: Define ConfidentialComputingGuestAttr
OvmfPkg/PlatformPei: set PcdConfidentialComputingAttr when SEV is
UefiCpuPkg/MpInitLib: use PcdConfidentialComputingAttr to check SEV
UefiCpuPkg: add PcdGhcbHypervisorFeatures
OvmfPkg/PlatformPei: set the Hypervisor Features PCD
MdePkg/GHCB: increase the GHCB protocol max version
UefiCpuPkg/MpLib: add support to register GHCB GPA when SEV-SNP is
OvmfPkg/MemEncryptSevLib: change the page state in the RMP table
OvmfPkg/MemEncryptSevLib: skip page state change for Mmio address
OvmfPkg/PlatformPei: mark cpuid and secrets memory reserved in EFI map
OvmfPkg/AmdSev: expose the SNP reserved pages through configuration

Michael Roth (3):
OvmfPkg/ResetVector: use SEV-SNP-validated CPUID values
OvmfPkg/VmgExitLib: use SEV-SNP-validated CPUID values
UefiCpuPkg/MpInitLib: use BSP to do extended topology check

Tom Lendacky (1):
UefiCpuPkg/MpInitLib: Use SEV-SNP AP Creation NAE event to launch APs

OvmfPkg/OvmfPkg.dec | 19 +
UefiCpuPkg/UefiCpuPkg.dec | 9 +
OvmfPkg/AmdSev/AmdSevX64.dsc | 5 +-
OvmfPkg/Bhyve/BhyveX64.dsc | 5 +-
OvmfPkg/OvmfPkgIa32.dsc | 1 +
OvmfPkg/OvmfPkgIa32X64.dsc | 6 +-
OvmfPkg/OvmfPkgX64.dsc | 5 +-
OvmfPkg/OvmfXen.dsc | 5 +-
OvmfPkg/OvmfPkgX64.fdf | 6 +
OvmfPkg/AmdSevDxe/AmdSevDxe.inf | 7 +
.../DxeMemEncryptSevLib.inf | 3 +
.../PeiMemEncryptSevLib.inf | 25 +
.../SecMemEncryptSevLib.inf | 3 +
OvmfPkg/Library/VmgExitLib/SecVmgExitLib.inf | 2 +
OvmfPkg/Library/VmgExitLib/VmgExitLib.inf | 3 +
OvmfPkg/PlatformPei/PlatformPei.inf | 8 +
OvmfPkg/ResetVector/ResetVector.inf | 11 +
OvmfPkg/Sec/SecMain.inf | 4 +
UefiCpuPkg/Library/MpInitLib/DxeMpInitLib.inf | 5 +-
UefiCpuPkg/Library/MpInitLib/PeiMpInitLib.inf | 5 +-
MdePkg/Include/Register/Amd/Ghcb.h | 2 +-
.../Guid/ConfidentialComputingSevSnpBlob.h | 33 ++
OvmfPkg/Include/Library/MemEncryptSevLib.h | 26 +
.../X64/SnpPageStateChange.h | 36 ++
.../BaseMemEncryptSevLib/X64/VirtualMemory.h | 19 +
OvmfPkg/PlatformPei/Platform.h | 5 +
OvmfPkg/Sec/AmdSev.h | 95 ++++
.../Include/ConfidentialComputingGuestAttr.h | 25 +
UefiCpuPkg/Library/MpInitLib/MpLib.h | 60 +++
OvmfPkg/AmdSevDxe/AmdSevDxe.c | 23 +
.../DxeMemEncryptSevLibInternal.c | 27 ++
.../Ia32/MemEncryptSevLib.c | 17 +
.../PeiMemEncryptSevLibInternal.c | 27 ++
.../SecMemEncryptSevLibInternal.c | 19 +
.../X64/DxeSnpSystemRamValidate.c | 40 ++
.../X64/PeiDxeVirtualMemory.c | 167 ++++++-
.../X64/PeiSnpSystemRamValidate.c | 163 +++++++
.../X64/SecSnpSystemRamValidate.c | 82 ++++
.../X64/SnpPageStateChangeInternal.c | 294 ++++++++++++
OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c | 444 ++++++++++++++++--
OvmfPkg/PlatformPei/AmdSev.c | 235 +++++++++
OvmfPkg/PlatformPei/MemDetect.c | 2 +
OvmfPkg/Sec/AmdSev.c | 316 +++++++++++++
OvmfPkg/Sec/SecMain.c | 160 +------
UefiCpuPkg/Library/MpInitLib/DxeMpLib.c | 16 +-
UefiCpuPkg/Library/MpInitLib/Ia32/AmdSev.c | 70 +++
UefiCpuPkg/Library/MpInitLib/MpLib.c | 122 ++++-
UefiCpuPkg/Library/MpInitLib/PeiMpLib.c | 4 +-
UefiCpuPkg/Library/MpInitLib/X64/AmdSev.c | 261 ++++++++++
OvmfPkg/FvmainCompactScratchEnd.fdf.inc | 5 +
OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm | 17 +
OvmfPkg/ResetVector/Ia32/AmdSev.asm | 86 +++-
OvmfPkg/ResetVector/ResetVector.nasmb | 35 ++
OvmfPkg/ResetVector/X64/OvmfMetadata.asm | 113 +++++
UefiCpuPkg/Library/MpInitLib/MpEqu.inc | 2 +
UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm | 80 ++++
56 files changed, 3034 insertions(+), 231 deletions(-)
create mode 100644 OvmfPkg/Include/Guid/ConfidentialComputingSevSnpBlob.h
create mode 100644 OvmfPkg/Library/BaseMemEncryptSevLib/X64/SnpPageStateChange.h
create mode 100644 OvmfPkg/Sec/AmdSev.h
create mode 100644 UefiCpuPkg/Include/ConfidentialComputingGuestAttr.h
create mode 100644 OvmfPkg/Library/BaseMemEncryptSevLib/X64/DxeSnpSystemRamValidate.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/Sec/AmdSev.c
create mode 100644 UefiCpuPkg/Library/MpInitLib/Ia32/AmdSev.c
create mode 100644 UefiCpuPkg/Library/MpInitLib/X64/AmdSev.c
create mode 100644 OvmfPkg/ResetVector/X64/OvmfMetadata.asm