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From: "Brijesh Singh" <brijesh.singh@amd.com>
To: <devel@edk2.groups.io>
Cc: James Bottomley <jejb@linux.ibm.com>, Min Xu <min.m.xu@intel.com>,
	"Jiewen Yao" <jiewen.yao@intel.com>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	"Jordan Justen" <jordan.l.justen@intel.com>,
	Ard Biesheuvel <ardb+tianocore@kernel.org>,
	Erdem Aktas <erdemaktas@google.com>,
	"Michael Roth" <Michael.Roth@amd.com>,
	Gerd Hoffmann <kraxel@redhat.com>,
	Brijesh Singh <brijesh.singh@amd.com>,
	Michael Roth <michael.roth@amd.com>
Subject: [PATCH v10 07/32] OvmfPkg/ResetVector: pre-validate the data pages used in SEC phase
Date: Tue, 19 Oct 2021 14:39:09 -0500	[thread overview]
Message-ID: <20211019193934.1052465-8-brijesh.singh@amd.com> (raw)
In-Reply-To: <20211019193934.1052465-1-brijesh.singh@amd.com>

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3275

An SEV-SNP guest requires that private memory (aka pages mapped encrypted)
must be validated before being accessed.

The validation process consist of the following sequence:

1) Set the memory encryption attribute in the page table (aka C-bit).
   Note: If the processor is in non-PAE mode, then all the memory accesses
   are considered private.
2) Add the memory range as private in the RMP table. This can be performed
   using the Page State Change VMGEXIT defined in the GHCB specification.
3) Use the PVALIDATE instruction to set the Validated Bit in the RMP table.

During the guest creation time, the VMM encrypts the OVMF_CODE.fd using
the SEV-SNP firmware provided LAUNCH_UPDATE_DATA command. In addition to
encrypting the content, the command also validates the memory region.
This allows us to execute the code without going through the validation
sequence.

During execution, the reset vector need to access some data pages
(such as page tables, SevESWorkarea, Sec stack). The data pages are
accessed as private memory. The data pages are not part of the
OVMF_CODE.fd, so they were not validated during the guest creation.

There are two approaches we can take to validate the data pages before
the access:

a) Enhance the OVMF reset vector code to validate the pages as described
   above (go through step 2 - 3).
OR
b) Validate the pages during the guest creation time. The SEV firmware
   provides a command which can be used by the VMM to validate the pages
   without affecting the measurement of the launch.

Approach #b seems much simpler; it does not require any changes to the
OVMF reset vector code.

Update the OVMF metadata with the list of regions that must be
pre-validated by the VMM before the boot.

Cc: Michael Roth <michael.roth@amd.com>
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: Erdem Aktas <erdemaktas@google.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 OvmfPkg/ResetVector/ResetVector.inf         |  1 +
 OvmfPkg/ResetVector/ResetVector.nasmb       | 13 +++++++++++++
 OvmfPkg/ResetVector/X64/OvmfSevMetadata.asm | 15 +++++++++++++++
 3 files changed, 29 insertions(+)

diff --git a/OvmfPkg/ResetVector/ResetVector.inf b/OvmfPkg/ResetVector/ResetVector.inf
index 4cb81a3233f0..278776a0b02e 100644
--- a/OvmfPkg/ResetVector/ResetVector.inf
+++ b/OvmfPkg/ResetVector/ResetVector.inf
@@ -48,6 +48,7 @@ [Pcd]
 [FixedPcd]
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfCpuidBase
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfCpuidSize
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfPeiMemFvBase
   gUefiOvmfPkgTokenSpaceGuid.PcdSevLaunchSecretBase
   gUefiOvmfPkgTokenSpaceGuid.PcdSevLaunchSecretSize
   gUefiOvmfPkgTokenSpaceGuid.PcdQemuHashTableBase
diff --git a/OvmfPkg/ResetVector/ResetVector.nasmb b/OvmfPkg/ResetVector/ResetVector.nasmb
index 1c411a42f1b3..a7831eee23af 100644
--- a/OvmfPkg/ResetVector/ResetVector.nasmb
+++ b/OvmfPkg/ResetVector/ResetVector.nasmb
@@ -82,6 +82,19 @@
   %define SEV_SNP_SECRETS_SIZE  (FixedPcdGet32 (PcdOvmfSnpSecretsSize))
   %define CPUID_BASE  (FixedPcdGet32 (PcdOvmfCpuidBase))
   %define CPUID_SIZE  (FixedPcdGet32 (PcdOvmfCpuidSize))
+  %define SNP_SEC_MEM_BASE_DESC_1 (FixedPcdGet32 (PcdOvmfSecPageTablesBase))
+  %define SNP_SEC_MEM_SIZE_DESC_1 (FixedPcdGet32 (PcdOvmfSecGhcbBase) - SNP_SEC_MEM_BASE_DESC_1)
+  ;
+  ; The PcdOvmfSecGhcbBase reserves two GHCB pages. The first page is used
+  ; as GHCB shared page and second is used for bookkeeping to support the
+  ; nested GHCB in SEC phase. The bookkeeping page is mapped private. The VMM
+  ; does not need to validate the shared page but it need to validate the
+  ; bookkeeping page.
+  ;
+  %define SNP_SEC_MEM_BASE_DESC_2 (GHCB_BASE + 0x1000)
+  %define SNP_SEC_MEM_SIZE_DESC_2 (SEV_SNP_SECRETS_BASE - SNP_SEC_MEM_BASE_DESC_2)
+  %define SNP_SEC_MEM_BASE_DESC_3 (CPUID_BASE + CPUID_SIZE)
+  %define SNP_SEC_MEM_SIZE_DESC_3 (FixedPcdGet32 (PcdOvmfPeiMemFvBase) - SNP_SEC_MEM_BASE_DESC_3)
 %include "Ia32/Flat32ToFlat64.asm"
 %include "Ia32/AmdSev.asm"
 %include "Ia32/PageTables64.asm"
diff --git a/OvmfPkg/ResetVector/X64/OvmfSevMetadata.asm b/OvmfPkg/ResetVector/X64/OvmfSevMetadata.asm
index 38cc8809a7fb..b869b24e7c1f 100644
--- a/OvmfPkg/ResetVector/X64/OvmfSevMetadata.asm
+++ b/OvmfPkg/ResetVector/X64/OvmfSevMetadata.asm
@@ -43,6 +43,16 @@ _Descriptor:
   DD OVMF_SEV_METADATA_VERSION                        ; Version
   DD (OvmfSevGuidedStructureEnd - _Descriptor - 16) / 12 ; Number of sections
 
+; Region need to be pre-validated by the hypervisor
+PreValidate1:
+  DD  SNP_SEC_MEM_BASE_DESC_1
+  DD  SNP_SEC_MEM_SIZE_DESC_1
+  DD  OVMF_SECTION_TYPE_SNP_SEC_MEM
+PreValidate2:
+  DD  SNP_SEC_MEM_BASE_DESC_2
+  DD  SNP_SEC_MEM_SIZE_DESC_2
+  DD  OVMF_SECTION_TYPE_SNP_SEC_MEM
+
 ; SEV-SNP Secrets page
 SevSnpSecrets:
   DD  SEV_SNP_SECRETS_BASE
@@ -55,5 +65,10 @@ CpuidSec:
   DD  CPUID_SIZE
   DD  OVMF_SECTION_TYPE_CPUID
 
+; Region need to be pre-validated by the hypervisor
+PreValidate3:
+  DD  SNP_SEC_MEM_BASE_DESC_3
+  DD  SNP_SEC_MEM_SIZE_DESC_3
+  DD  OVMF_SECTION_TYPE_SNP_SEC_MEM
 OvmfSevGuidedStructureEnd:
   ALIGN   16
-- 
2.25.1


  parent reply	other threads:[~2021-10-19 19:40 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-19 19:39 [PATCH v10 00/32] Add AMD Secure Nested Paging (SEV-SNP) support Brijesh Singh
2021-10-19 19:39 ` [PATCH v10 01/32] OvmfPkg/SecMain: move SEV specific routines in AmdSev.c Brijesh Singh
2021-10-19 19:39 ` [PATCH v10 02/32] UefiCpuPkg/MpInitLib: " Brijesh Singh
2021-10-19 19:39 ` [PATCH v10 03/32] OvmfPkg/ResetVector: move clearing GHCB in SecMain Brijesh Singh
2021-10-19 19:39 ` [PATCH v10 04/32] OvmfPkg/ResetVector: introduce SEV metadata descriptor for VMM use Brijesh Singh
2021-10-19 19:39 ` [PATCH v10 05/32] OvmfPkg: reserve SNP secrets page Brijesh Singh
2021-10-19 19:39 ` [PATCH v10 06/32] OvmfPkg: reserve CPUID page Brijesh Singh
2021-10-19 19:39 ` Brijesh Singh [this message]
2021-10-19 19:39 ` [PATCH v10 08/32] OvmfPkg/ResetVector: use SEV-SNP-validated CPUID values Brijesh Singh
2021-10-19 19:39 ` [PATCH v10 09/32] OvmfPkg/MemEncryptSevLib: add MemEncryptSevSnpEnabled() Brijesh Singh
2021-10-19 19:39 ` [PATCH v10 10/32] OvmfPkg/SecMain: register GHCB gpa for the SEV-SNP guest Brijesh Singh
2021-10-19 19:39 ` [PATCH v10 11/32] OvmfPkg/VmgExitLib: use SEV-SNP-validated CPUID values Brijesh Singh
2021-10-19 19:39 ` [PATCH v10 12/32] OvmfPkg/PlatformPei: register GHCB gpa for the SEV-SNP guest Brijesh Singh
2021-10-19 19:39 ` [PATCH v10 13/32] OvmfPkg/AmdSevDxe: do not use extended PCI config space Brijesh Singh
2021-10-19 19:39 ` [PATCH v10 14/32] OvmfPkg/MemEncryptSevLib: add support to validate system RAM Brijesh Singh
2021-10-19 19:39 ` [PATCH v10 15/32] OvmfPkg/MemEncryptSevLib: add function to check the VMPL0 Brijesh Singh
2021-10-19 19:39 ` [PATCH v10 16/32] OvmfPkg/BaseMemEncryptSevLib: skip the pre-validated system RAM Brijesh Singh
2021-10-19 19:39 ` [PATCH v10 17/32] OvmfPkg/MemEncryptSevLib: add support to validate > 4GB memory in PEI phase Brijesh Singh
2021-10-20  4:54   ` Gerd Hoffmann
2021-10-19 19:39 ` [PATCH v10 18/32] OvmfPkg/SecMain: validate the memory used for decompressing Fv Brijesh Singh
2021-10-19 19:39 ` [PATCH v10 19/32] OvmfPkg/PlatformPei: validate the system RAM when SNP is active Brijesh Singh
2021-10-19 19:39 ` [PATCH v10 20/32] UefiCpuPkg: Define ConfidentialComputingGuestAttr Brijesh Singh
2021-10-20  4:55   ` Gerd Hoffmann
2021-10-19 19:39 ` [PATCH v10 21/32] OvmfPkg/PlatformPei: set PcdConfidentialComputingAttr when SEV is active Brijesh Singh
2021-10-19 19:39 ` [PATCH v10 22/32] UefiCpuPkg/MpInitLib: use PcdConfidentialComputingAttr to check SEV status Brijesh Singh
2021-10-20  4:58   ` Gerd Hoffmann
2021-10-19 19:39 ` [PATCH v10 23/32] UefiCpuPkg: add PcdGhcbHypervisorFeatures Brijesh Singh
2021-10-19 19:39 ` [PATCH v10 24/32] OvmfPkg/PlatformPei: set the Hypervisor Features PCD Brijesh Singh
2021-10-19 19:39 ` [PATCH v10 25/32] MdePkg/GHCB: increase the GHCB protocol max version Brijesh Singh
2021-10-19 19:39 ` [PATCH v10 26/32] UefiCpuPkg/MpLib: add support to register GHCB GPA when SEV-SNP is enabled Brijesh Singh
2021-10-19 19:39 ` [PATCH v10 27/32] UefiCpuPkg/MpInitLib: use BSP to do extended topology check Brijesh Singh
2021-10-19 19:39 ` [PATCH v10 28/32] OvmfPkg/MemEncryptSevLib: change the page state in the RMP table Brijesh Singh
2021-10-19 19:39 ` [PATCH v10 29/32] OvmfPkg/MemEncryptSevLib: skip page state change for Mmio address Brijesh Singh
2021-10-19 19:39 ` [PATCH v10 30/32] OvmfPkg/PlatformPei: mark cpuid and secrets memory reserved in EFI map Brijesh Singh
2021-10-20  5:00   ` Gerd Hoffmann
2021-10-19 19:39 ` [PATCH v10 31/32] OvmfPkg/AmdSev: expose the SNP reserved pages through configuration table Brijesh Singh
2021-10-19 19:39 ` [PATCH v10 32/32] UefiCpuPkg/MpInitLib: Use SEV-SNP AP Creation NAE event to launch APs Brijesh Singh

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