Re: [PATCH v1 0/2] efi/tpm: Preserve event log without changing x86 E820

["Ard Biesheuvel" <ardb@kernel.org>]

Hi Jazz,

On Tue, 1 Sep 2026, at 13:34, Jasmeet (Jazz) Bhatia wrote:
> The EFI stub currently allocates the TPM event log as
> EFI_ACPI_RECLAIM_MEMORY. On x86, this becomes an ACPI data entry
> in the E820 map.
>
> On a Framework Laptop 16 (AMD Ryzen AI 300 Series), the EFI allocator
> can place this allocation at different physical addresses across boots.
> Since x86 hibernation validates architecture-specific data from
> the firmware E820 map, this causes an otherwise valid hibernation image
> to be rejected on resume with the following error:
>
>   Hibernate inconsistent memory map detected!
>   PM: hibernation: Image mismatch: architecture specific data
>
> Allocating the event log as EFI_LOADER_DATA avoids changing the E820
> map, but doing that alone would regress the kexec corruption issue fixed
> by commit 77d48d39e991 ("efistub/tpm: Use ACPI reclaim memory for event
> log to avoid corruption").
>

As I replied in the other thread, I am not convinced preserving the TPM
event log across a kexec makes sense to begin with. This is the firmware's
view of the state of the TPM PCRs when it handed over the system to the
first OS.

If the first OS boots, loads a kexec kernel and then boots it without
measuring any of that into the TPM, the TPM event log will match the
TPM state, but this is meaningless because of the missing measurements,
and the attestation chain is broken.

If the first OS does perform TPM measurements, it would need to record
them into a log and pass that on to the kexec'ed in some implementation
specific way - it cannot use the existing TPM event log for that.

TL;DR perhaps we should just discard the TPM event log reference from
the EFI config tables after consuming it. Or add a special case to the
kexec code to disregard it.