[PATCH v10 30/32] OvmfPkg/PlatformPei: mark cpuid and secrets memory reserved in EFI map


Brijesh Singh
 

When SEV-SNP is active, the CPUID and Secrets memory range contains the
information that is used during the VM boot. The content need to be persist
across the kexec boot. Mark the memory range as Reserved in the EFI map
so that guest OS or firmware does not use the range as a system RAM.

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>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
OvmfPkg/PlatformPei/PlatformPei.inf | 4 ++++
OvmfPkg/PlatformPei/Platform.h | 5 +++++
OvmfPkg/PlatformPei/AmdSev.c | 31 +++++++++++++++++++++++++++++
OvmfPkg/PlatformPei/MemDetect.c | 2 ++
4 files changed, 42 insertions(+)

diff --git a/OvmfPkg/PlatformPei/PlatformPei.inf b/OvmfPkg/PlatformPei/PlatformPei.inf
index 3c05b550e4bd..1c56ba275835 100644
--- a/OvmfPkg/PlatformPei/PlatformPei.inf
+++ b/OvmfPkg/PlatformPei/PlatformPei.inf
@@ -111,6 +111,8 @@ [Pcd]
gUefiCpuPkgTokenSpaceGuid.PcdGhcbHypervisorFeatures

[FixedPcd]
+ gUefiOvmfPkgTokenSpaceGuid.PcdOvmfCpuidBase
+ gUefiOvmfPkgTokenSpaceGuid.PcdOvmfCpuidSize
gEfiMdePkgTokenSpaceGuid.PcdPciExpressBaseAddress
gEmbeddedTokenSpaceGuid.PcdMemoryTypeEfiACPIMemoryNVS
gEmbeddedTokenSpaceGuid.PcdMemoryTypeEfiACPIReclaimMemory
@@ -121,6 +123,8 @@ [FixedPcd]
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBackupSize
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfWorkAreaBase
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfWorkAreaSize
+ gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecretsBase
+ gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecretsSize

[FeaturePcd]
gUefiOvmfPkgTokenSpaceGuid.PcdCsmEnable
diff --git a/OvmfPkg/PlatformPei/Platform.h b/OvmfPkg/PlatformPei/Platform.h
index 8b1d270c2b0b..4169019b4c07 100644
--- a/OvmfPkg/PlatformPei/Platform.h
+++ b/OvmfPkg/PlatformPei/Platform.h
@@ -102,6 +102,11 @@ AmdSevInitialize (
VOID
);

+VOID
+SevInitializeRam (
+ VOID
+ );
+
extern EFI_BOOT_MODE mBootMode;

extern BOOLEAN mS3Supported;
diff --git a/OvmfPkg/PlatformPei/AmdSev.c b/OvmfPkg/PlatformPei/AmdSev.c
index b71a4a7304f7..133382407bc5 100644
--- a/OvmfPkg/PlatformPei/AmdSev.c
+++ b/OvmfPkg/PlatformPei/AmdSev.c
@@ -414,3 +414,34 @@ AmdSevInitialize (
ASSERT_RETURN_ERROR (PcdStatus);

}
+
+/**
+ The function performs SEV specific region initialization.
+
+ **/
+VOID
+SevInitializeRam (
+ VOID
+ )
+{
+ if (MemEncryptSevSnpIsEnabled ()) {
+ //
+ // If SEV-SNP is enabled, reserve the Secrets and CPUID memory area.
+ //
+ // This memory range is given to the PSP by the hypervisor to populate
+ // the information used during the SNP VM boots, and it need to persist
+ // across the kexec boots. Mark it as EfiReservedMemoryType so that
+ // the guest firmware and OS does not use it as a system memory.
+ //
+ BuildMemoryAllocationHob (
+ (EFI_PHYSICAL_ADDRESS)(UINTN) PcdGet32 (PcdOvmfSnpSecretsBase),
+ (UINT64)(UINTN) PcdGet32 (PcdOvmfSnpSecretsSize),
+ EfiReservedMemoryType
+ );
+ BuildMemoryAllocationHob (
+ (EFI_PHYSICAL_ADDRESS)(UINTN) PcdGet32 (PcdOvmfCpuidBase),
+ (UINT64)(UINTN) PcdGet32 (PcdOvmfCpuidSize),
+ EfiReservedMemoryType
+ );
+ }
+}
diff --git a/OvmfPkg/PlatformPei/MemDetect.c b/OvmfPkg/PlatformPei/MemDetect.c
index d736b85e0d90..058bb394f0df 100644
--- a/OvmfPkg/PlatformPei/MemDetect.c
+++ b/OvmfPkg/PlatformPei/MemDetect.c
@@ -821,6 +821,8 @@ InitializeRamRegions (
{
QemuInitializeRam ();

+ SevInitializeRam ();
+
if (mS3Supported && mBootMode != BOOT_ON_S3_RESUME) {
//
// This is the memory range that will be used for PEI on S3 resume
--
2.25.1


Gerd Hoffmann
 

On Tue, Oct 19, 2021 at 02:39:32PM -0500, Brijesh Singh wrote:
When SEV-SNP is active, the CPUID and Secrets memory range contains the
information that is used during the VM boot. The content need to be persist
across the kexec boot. Mark the memory range as Reserved in the EFI map
so that guest OS or firmware does not use the range as a system RAM.

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>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>