[edk2-devel] [PATCH 1/4] OvmfPkg/AmdSevDxe: Allocate SEV-SNP CC blob as EfiACPIReclaimMemory

[Yao, Jiewen]

Are you sure you want to use EfiACPIReclaimMemory ?

Usually EfiACPIReclaimMemory is only for ACPI table, which can be reclaimed and used by OS, after copy ACPI table.

If you want to claim the memory owned by firmware (not owned by OS), you need use ACPINvs or reserved.


Although I don't fully understand SEV, this seems suspicious.

Please double confirm if this is really you want.

Thank you
Yao, Jiewen


> -----Original Message-----
> From: devel at edk2.groups.io <devel at edk2.groups.io> On Behalf Of Roth,
> Michael via groups.io
> Sent: Thursday, December 22, 2022 12:07 AM
> To: devel at edk2.groups.io
> Cc: Tom Lendacky <thomas.lendacky at amd.com>; Ni, Ray
> <ray.ni at intel.com>; Dov Murik <dovmurik at linux.ibm.com>
> Subject: [edk2-devel] [PATCH 1/4] OvmfPkg/AmdSevDxe: Allocate SEV-SNP CC
> blob as EfiACPIReclaimMemory
> 
> The SEV-SNP Confidential Computing blob contains metadata that should
> remain accessible for the life of the guest. Allocate it as
> EfiACPIReclaimMemory to ensure the memory isn't overwritten by the guest
> operating system later.
> 
> Reported-by: Dov Murik <dovmurik at linux.ibm.com>
> Suggested-by: Dov Murik <dovmurik at linux.ibm.com>
> Signed-off-by: Michael Roth <michael.roth at amd.com>
> ---
>  OvmfPkg/AmdSevDxe/AmdSevDxe.c | 62 +++++++++++++++++++++++++++---
> -----
>  1 file changed, 48 insertions(+), 14 deletions(-)
> 
> diff --git a/OvmfPkg/AmdSevDxe/AmdSevDxe.c
> b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
> index 662d3c4ccb..8dfda961d7 100644
> --- a/OvmfPkg/AmdSevDxe/AmdSevDxe.c
> +++ b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
> @@ -21,15 +21,36 @@
>  #include <Guid/ConfidentialComputingSevSnpBlob.h>
> 
>  #include <Library/PcdLib.h>
> 
> 
> 
> -STATIC CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION
> mSnpBootDxeTable = {
> 
> -  SIGNATURE_32 ('A',                                    'M', 'D', 'E'),
> 
> -  1,
> 
> -  0,
> 
> -  (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfSnpSecretsBase),
> 
> -  FixedPcdGet32 (PcdOvmfSnpSecretsSize),
> 
> -  (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfCpuidBase),
> 
> -  FixedPcdGet32 (PcdOvmfCpuidSize),
> 
> -};
> 
> +STATIC
> 
> +EFI_STATUS
> 
> +AllocateConfidentialComputingBlob (
> 
> +  OUT CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  **CcBlobPtr
> 
> +  )
> 
> +{
> 
> +  EFI_STATUS                                Status;
> 
> +  CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  *CcBlob;
> 
> +
> 
> +  Status = gBS->AllocatePool (
> 
> +                  EfiACPIReclaimMemory,
> 
> +                  sizeof (CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION),
> 
> +                  (VOID **)&CcBlob
> 
> +                  );
> 
> +  if (EFI_ERROR (Status)) {
> 
> +    return Status;
> 
> +  }
> 
> +
> 
> +  CcBlob->Header                 = SIGNATURE_32 ('A', 'M', 'D', 'E');
> 
> +  CcBlob->Version                = 1;
> 
> +  CcBlob->Reserved1              = 0;
> 
> +  CcBlob->SecretsPhysicalAddress = (UINT64)(UINTN)FixedPcdGet32
> (PcdOvmfSnpSecretsBase);
> 
> +  CcBlob->SecretsSize            = FixedPcdGet32 (PcdOvmfSnpSecretsSize);
> 
> +  CcBlob->CpuidPhysicalAddress   = (UINT64)(UINTN)FixedPcdGet32
> (PcdOvmfCpuidBase);
> 
> +  CcBlob->CpuidLSize             = FixedPcdGet32 (PcdOvmfCpuidSize);
> 
> +
> 
> +  *CcBlobPtr = CcBlob;
> 
> +
> 
> +  return EFI_SUCCESS;
> 
> +}
> 
> 
> 
>  EFI_STATUS
> 
>  EFIAPI
> 
> @@ -38,10 +59,11 @@ AmdSevDxeEntryPoint (
>    IN EFI_SYSTEM_TABLE  *SystemTable
> 
>    )
> 
>  {
> 
> -  EFI_STATUS                       Status;
> 
> -  EFI_GCD_MEMORY_SPACE_DESCRIPTOR  *AllDescMap;
> 
> -  UINTN                            NumEntries;
> 
> -  UINTN                            Index;
> 
> +  EFI_STATUS                                Status;
> 
> +  EFI_GCD_MEMORY_SPACE_DESCRIPTOR           *AllDescMap;
> 
> +  UINTN                                     NumEntries;
> 
> +  UINTN                                     Index;
> 
> +  CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  *SnpBootDxeTable;
> 
> 
> 
>    //
> 
>    // Do nothing when SEV is not enabled
> 
> @@ -147,6 +169,18 @@ AmdSevDxeEntryPoint (
>      }
> 
>    }
> 
> 
> 
> +  Status = AllocateConfidentialComputingBlob (&SnpBootDxeTable);
> 
> +  if (EFI_ERROR (Status)) {
> 
> +    DEBUG ((
> 
> +      DEBUG_ERROR,
> 
> +      "%a: AllocateConfidentialComputingBlob(): %r\n",
> 
> +      __FUNCTION__,
> 
> +      Status
> 
> +      ));
> 
> +    ASSERT (FALSE);
> 
> +    CpuDeadLoop ();
> 
> +  }
> 
> +
> 
>    //
> 
>    // 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.
> 
> @@ -154,7 +188,7 @@ AmdSevDxeEntryPoint (
>    if (MemEncryptSevSnpIsEnabled ()) {
> 
>      return gBS->InstallConfigurationTable (
> 
>                    &gConfidentialComputingSevSnpBlobGuid,
> 
> -                  &mSnpBootDxeTable
> 
> +                  SnpBootDxeTable
> 
>                    );
> 
>    }
> 
> 
> 
> --
> 2.25.1
> 
> 
> 
> 
> 



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