Hello,

SEV/SEVES guest boot fails with AMDSEV OVMF package built using upstream edk2 master [commit head: 2fbaaa96d11ad61a9133df1728e3fe965d1457a5].

SEV/SEVES guest boot with AMDSEV package gets stuck at below point:

Plain Text

2024-06-26 04:38:02: FetchBlob: loading 14332416 bytes for "kernel"
2024-06-26 04:38:02: Select Item: 0x18
2024-06-26 04:38:02: Select Item: 0x11
2024-06-26 04:38:02: VerifyBlob: Found GUID 4DE79437-ABD2-427F-B835-D5B172D2045B in table
2024-06-26 04:38:02: VerifyBlob: Hash comparison succeeded for "kernel"
2024-06-26 04:38:02: Select Item: 0xB
2024-06-26 04:38:02: VerifyBlob: Found GUID 44BAF731-3A2F-4BD7-9AF1-41E29169781D in table
2024-06-26 04:38:02: VerifyBlob: Blob Specified in Hash Table was not Provided

--> Hung here

This was working until yesterday [commit head: be38c01], where we can see boot was proceeding

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2024-06-25 03:13:23: VerifyBlob: Found GUID 4DE79437-ABD2-427F-B835-D5B172D2045B in table
2024-06-25 03:13:23: VerifyBlob: Hash comparison succeeded for "kernel"
2024-06-25 03:13:23: Select Item: 0xB
2024-06-25 03:13:23: VerifyBlob: Found GUID 44BAF731-3A2F-4BD7-9AF1-41E29169781D in table
2024-06-25 03:13:23: VerifyBlob: Hash comparison succeeded for "initrd"
2024-06-25 03:13:23: Select Item: 0x14
2024-06-25 03:13:23: FetchBlob: loading 120 bytes for "cmdline"
2024-06-25 03:13:23: Select Item: 0x15
2024-06-25 03:13:23: VerifyBlob: Found GUID 97D02DD8-BD20-4C94-AA78-E7714D36AB2A in table
2024-06-25 03:13:23: VerifyBlob: Hash comparison succeeded for "cmdline"

After this patch got merged the regression is seen.

Thanks,

Srikanth Aithal

On 5/7/2024 1:57 AM, Tobin Feldman-Fitzthum via groups.io wrote:

The AmdSev package has a so-called BlobVerifier, which
is meant to extend the TCB of a confidential guest
(SEV or SNP) to include components provided via fw_cfg
such as initrd, kernel, kernel params.

This series fixes a few implementation errors in the
blob verifier. One common theme is that the verifier
currently fails to halt the boot when an invalid blob
is detected. This can lead to a confidential guest
having a launch measurement that does not reflect the
guest TCB.

This series could also help us move towards consolidating
the AmdSev package back into the OvmfPkg although more
discussion will be needed on this.

Thank you for Ryan Savino at AMD for pointing out
some of these issues.

Tobin Feldman-Fitzthum (2):
  AmdSev: Rework Blob Verifier
  AmdSev: Halt on failed blob allocation

 .../BlobVerifierSevHashes.c                   | 56 ++++++++++++++++---
 OvmfPkg/Include/Library/BlobVerifierLib.h     | 14 +++--
 .../BlobVerifierLibNull/BlobVerifierNull.c    | 13 +++--
 .../QemuKernelLoaderFsDxe.c                   |  9 ++-
 4 files changed, 69 insertions(+), 23 deletions(-)

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