On 9/28/22 10:33, Dionna Glaze wrote:

From: Sophia Wolf <phiawolf@...>
When a guest OS does not support unaccepted memory, the unaccepted
memory must be accepted before returning a memory map to the caller.
EfiMemoryAcceptProtocol is defined in MdePkg and is implemented /
Installed in AmdSevDxe for AMD SEV-SNP memory acceptance.
Cc: Gerd Hoffmann <kraxel@...>
Cc: James Bottomley <jejb@...>
Cc: Jiewen Yao <jiewen.yao@...>
Cc: Tom Lendacky <thomas.lendacky@...>
Signed-off-by: Sophia Wolf <phiawolf@...>
---
OvmfPkg/AmdSevDxe/AmdSevDxe.c | 34 ++++++++++++++++++++
OvmfPkg/AmdSevDxe/AmdSevDxe.inf | 3 ++
OvmfPkg/Library/BaseMemEncryptSevLib/X64/DxeSnpSystemRamValidate.c | 24 +++++++++++---
3 files changed, 57 insertions(+), 4 deletions(-)
diff --git a/OvmfPkg/AmdSevDxe/AmdSevDxe.c b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
index 662d3c4ccb..09aa15165d 100644
--- a/OvmfPkg/AmdSevDxe/AmdSevDxe.c
+++ b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
@@ -20,6 +20,7 @@
#include <Library/UefiBootServicesTableLib.h>
#include <Guid/ConfidentialComputingSevSnpBlob.h>
#include <Library/PcdLib.h>
+#include <Protocol/MemoryAccept.h>
STATIC CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION mSnpBootDxeTable = {
SIGNATURE_32 ('A', 'M', 'D', 'E'),
@@ -31,6 +32,29 @@ STATIC CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION mSnpBootDxeTable = {
FixedPcdGet32 (PcdOvmfCpuidSize),
};
+STATIC EFI_HANDLE mAmdSevDxeHandle = NULL;
+
+STATIC
+EFI_STATUS
+EFIAPI
+AmdSevMemoryAccept (
+ IN EFI_MEMORY_ACCEPT_PROTOCOL *This,
+ IN EFI_PHYSICAL_ADDRESS StartAddress,
+ IN UINTN Size
+)
+{
+ MemEncryptSevSnpPreValidateSystemRam (
+ StartAddress,
+ EFI_SIZE_TO_PAGES (Size)

Sorry, I forgot to ask this earlier in the series, but is StartAddress guaranteed to be page-aligned and Size a multiple of 4KB? Should there be any asserts for those just in case?

Also, can Size be 0? In which case MemEncryptSevSnpPreValidateSystemRam() shouldn't be called?

+ );
+
+ return EFI_SUCCESS;
+}
+
+STATIC EFI_MEMORY_ACCEPT_PROTOCOL mMemoryAcceptProtocol = {
+ AmdSevMemoryAccept
+};
+
EFI_STATUS
EFIAPI
AmdSevDxeEntryPoint (
@@ -147,6 +171,16 @@ AmdSevDxeEntryPoint (
}
}
+ Status = gBS->InstallProtocolInterface (
+ &mAmdSevDxeHandle,
+ &gEfiMemoryAcceptProtocolGuid,
+ EFI_NATIVE_INTERFACE,
+ &mMemoryAcceptProtocol
+ );
+ if (EFI_ERROR (Status)) {
+ DEBUG ((DEBUG_ERROR, "Install EfiMemoryAcceptProtocol failed.\n"));
+ }

Should this only be installed for an SNP guest, e.g. put within the
"if (MemEncryptSevSnpIsEnabled ()) {" check?

Maybe use ASSERT_EFI_ERROR (Status)?

Thanks,
Tom

+
//
// If its SEV-SNP active guest then install the CONFIDENTIAL_COMPUTING_SEV_SNP_BLOB.
// It contains the location for both the Secrets and CPUID page.
diff --git a/OvmfPkg/AmdSevDxe/AmdSevDxe.inf b/OvmfPkg/AmdSevDxe/AmdSevDxe.inf
index 9acf860cf2..5ddddabc32 100644
--- a/OvmfPkg/AmdSevDxe/AmdSevDxe.inf
+++ b/OvmfPkg/AmdSevDxe/AmdSevDxe.inf
@@ -47,6 +47,9 @@
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecretsBase
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecretsSize
+[Protocols]
+ gEfiMemoryAcceptProtocolGuid
+
[Guids]
gConfidentialComputingSevSnpBlobGuid
diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/DxeSnpSystemRamValidate.c b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/DxeSnpSystemRamValidate.c
index d3a95e4913..ee3710f7b3 100644
--- a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/DxeSnpSystemRamValidate.c
+++ b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/DxeSnpSystemRamValidate.c
@@ -14,6 +14,7 @@
#include <Library/MemEncryptSevLib.h>
#include "SnpPageStateChange.h"
+#include "VirtualMemory.h"
/**
Pre-validate the system RAM when SEV-SNP is enabled in the guest VM.
@@ -29,12 +30,27 @@ MemEncryptSevSnpPreValidateSystemRam (
IN UINTN NumPages
)
{
+ EFI_STATUS Status;
+
if (!MemEncryptSevSnpIsEnabled ()) {
return;
}
- //
- // All the pre-validation must be completed in the PEI phase.
- //
- ASSERT (FALSE);
+ // DXE pre-validation may happen with the memory accept protocol.
+ // The protocol should only be called outside the prevalidated ranges
+ // that the PEI stage code explicitly skips. Specifically, only memory
+ // ranges that are classified as unaccepted.
+ if (BaseAddress >= SIZE_4GB) {
+ Status = InternalMemEncryptSevCreateIdentityMap1G (
+ 0,
+ BaseAddress,
+ EFI_PAGES_TO_SIZE (NumPages)
+ );
+ if (EFI_ERROR (Status)) {
+ ASSERT (FALSE);
+ CpuDeadLoop ();
+ }
+ }
+
+ InternalSetPageState (BaseAddress, NumPages, SevSnpPagePrivate, TRUE);
}