Re: [PATCH 1/3] OvmfPkg: Realize EfiMemoryAcceptProtocol in AmdSevDxe

["Yao, Jiewen" <jiewen.yao@intel.com>]

Acked-by: Jiewen Yao <Jiewen.yao@intel.com>

> -----Original Message-----
> From: Dionna Glaze <dionnaglaze@google.com>
> Sent: Wednesday, November 9, 2022 12:46 AM
> To: devel@edk2.groups.io
> Cc: Dionna Glaze <dionnaglaze@google.com>; Gerd Hoffmann
> <kraxel@redhat.com>; James Bottomley <jejb@linux.ibm.com>; Yao,
> Jiewen <jiewen.yao@intel.com>; Tom Lendacky
> <thomas.lendacky@amd.com>
> Subject: [PATCH 1/3] OvmfPkg: Realize EfiMemoryAcceptProtocol in
> AmdSevDxe
> 
> From: Sophia Wolf <phiawolf@google.com>
> 
> 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@redhat.com>
> Cc: James Bottomley <jejb@linux.ibm.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> 
> Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
> Signed-off-by: Dionna Glaze <dionnaglaze@google.com>
> ---
>  OvmfPkg/AmdSevDxe/AmdSevDxe.c                                      | 55
> ++++++++++++++++++--
>  OvmfPkg/AmdSevDxe/AmdSevDxe.inf                                    |  3 ++
> 
> OvmfPkg/Library/BaseMemEncryptSevLib/X64/DxeSnpSystemRamValidate.
> c | 24 +++++++--
>  3 files changed, 74 insertions(+), 8 deletions(-)
> 
> diff --git a/OvmfPkg/AmdSevDxe/AmdSevDxe.c
> b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
> index 662d3c4ccb..f7600c3c81 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 +32,40 @@ STATIC
> CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  mSnpBootDxeTable = {
>    FixedPcdGet32 (PcdOvmfCpuidSize),
>  };
> 
> +STATIC EFI_HANDLE  mAmdSevDxeHandle = NULL;
> +
> +#define IS_ALIGNED(x, y)  ((((x) & ((y) - 1)) == 0))
> +
> +STATIC
> +EFI_STATUS
> +EFIAPI
> +AmdSevMemoryAccept (
> +  IN EDKII_MEMORY_ACCEPT_PROTOCOL  *This,
> +  IN EFI_PHYSICAL_ADDRESS          StartAddress,
> +  IN UINTN                         Size
> +  )
> +{
> +  //
> +  // The StartAddress must be page-aligned, and the Size must be a
> positive
> +  // multiple of SIZE_4KB. Use an assert instead of returning an erros since
> +  // this is an EDK2-internal protocol.
> +  //
> +  ASSERT (IS_ALIGNED (StartAddress, SIZE_4KB));
> +  ASSERT (IS_ALIGNED (Size, SIZE_4KB));
> +  ASSERT (Size != 0);
> +
> +  MemEncryptSevSnpPreValidateSystemRam (
> +    StartAddress,
> +    EFI_SIZE_TO_PAGES (Size)
> +    );
> +
> +  return EFI_SUCCESS;
> +}
> +
> +STATIC EDKII_MEMORY_ACCEPT_PROTOCOL  mMemoryAcceptProtocol = {
> +  AmdSevMemoryAccept
> +};
> +
>  EFI_STATUS
>  EFIAPI
>  AmdSevDxeEntryPoint (
> @@ -147,11 +182,23 @@ AmdSevDxeEntryPoint (
>      }
>    }
> 
> -  //
> -  // 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.
> -  //
>    if (MemEncryptSevSnpIsEnabled ()) {
> +    //
> +    // Memory acceptance began being required in SEV-SNP, so install the
> +    // memory accept protocol implementation for a SEV-SNP active guest.
> +    //
> +    Status = gBS->InstallProtocolInterface (
> +                    &mAmdSevDxeHandle,
> +                    &gEdkiiMemoryAcceptProtocolGuid,
> +                    EFI_NATIVE_INTERFACE,
> +                    &mMemoryAcceptProtocol
> +                    );
> +    ASSERT_EFI_ERROR (Status);
> +
> +    //
> +    // 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.
> +    //
>      return gBS->InstallConfigurationTable (
>                    &gConfidentialComputingSevSnpBlobGuid,
>                    &mSnpBootDxeTable
> diff --git a/OvmfPkg/AmdSevDxe/AmdSevDxe.inf
> b/OvmfPkg/AmdSevDxe/AmdSevDxe.inf
> index 9acf860cf2..cd1b686c53 100644
> --- a/OvmfPkg/AmdSevDxe/AmdSevDxe.inf
> +++ b/OvmfPkg/AmdSevDxe/AmdSevDxe.inf
> @@ -47,6 +47,9 @@
>    gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecretsBase
>    gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecretsSize
> 
> +[Protocols]
> +  gEdkiiMemoryAcceptProtocolGuid
> +
>  [Guids]
>    gConfidentialComputingSevSnpBlobGuid
> 
> diff --git
> a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/DxeSnpSystemRamValidat
> e.c
> b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/DxeSnpSystemRamValida
> te.c
> index d3a95e4913..cbcdd46f52 100644
> ---
> a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/DxeSnpSystemRamValidat
> e.c
> +++
> b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/DxeSnpSystemRamValida
> te.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);
>  }
> --
> 2.38.1.431.g37b22c650d-goog