ACK/Cmnt: [SRU][N:gcp-6.14/P:gcp][PATCH 0/2] Fix attestation failure due to vTPM device error

[John Cabaj]

On 7/9/25 6:14 PM, Tim Whisonant wrote:
> BugLink: https://bugs.launchpad.net/bugs/2116287

This LP bug needs to be fixed to the bug itself and not the SWM kernel 
crank task.

Also ensure that Questing gets the same patch fix in a separate ML patch.

Acked-by: John Cabaj <john.cabaj at canonical.com>

> 
> SRU Justification:
> 
> [Impact]
> 
> UBUNTU: SAUCE: Revert "x86/mtrr: Rename mtrr_overwrite_state() to guest_force_mtrr_state()"
> 
> This reverts commit 6a5abeea9c72e1d2c538622b4cf66c80cc816fd3.
> 
> Google requests that this commit be removed from 6.14 kernels,
> namely plucky:linux-gcp and noble:linux-gcp-6.14. This commit
> along with 8e690b817e38769dc2fa0e7473e5a5dc1fc25795
> ("x86/kvm: Override default caching mode for SEV-SNP and TDX")
> are responsible for a TPM failure encountered on their TDX-enabled
> deployments. When present, error message "TPM fail - No TPM chip
> found" is observed during boot and the TPM is not available.
> 
> UBUNTU: SAUCE: Revert "x86/kvm: Override default caching mode for SEV-SNP and TDX"
> 
> This reverts commit 8e690b817e38769dc2fa0e7473e5a5dc1fc25795.
> 
> Google requests that this commit be removed from 6.14 kernels,
> namely plucky:linux-gcp and noble:linux-gcp-6.14. This commit
> along with 6a5abeea9c72e1d2c538622b4cf66c80cc816fd3
> ("x86/mtrr: Rename mtrr_overwrite_state() to guest_force_mtrr_state()")
> are responsible for a TPM failure encountered on their TDX-enabled
> deployments. When present, error message "TPM fail - No TPM chip
> found" is observed during boot and the TPM is not available.
> 
> [Fix]
> 
> Plucky:gcp     revert upstream commits
> Noble:gcp-6.14 revert upstream commits
> 
> [Test Plan]
> 
> Compile and boot tested.
> 
> [Where problems could occur]
> 
> This change is considered low risk as the commits were cleanly
> reverted, and the resulting kernel has been verified to resolve
> the issue both internally and by Google.
> 
> Tim Whisonant (2):
>    UBUNTU: SAUCE: Revert "x86/mtrr: Rename mtrr_overwrite_state() to
>      guest_force_mtrr_state()"
>    UBUNTU: SAUCE: Revert "x86/kvm: Override default caching mode for
>      SEV-SNP and TDX"
> 
>   arch/x86/hyperv/ivm.c              |  2 +-
>   arch/x86/include/asm/mtrr.h        | 10 +++++-----
>   arch/x86/kernel/cpu/mtrr/generic.c |  6 +++---
>   arch/x86/kernel/cpu/mtrr/mtrr.c    |  2 +-
>   arch/x86/kernel/kvm.c              |  4 ----
>   arch/x86/xen/enlighten_pv.c        |  4 ++--
>   6 files changed, 12 insertions(+), 16 deletions(-)
>