The feature_mask seems unable to correctly configure whether to enable the hardware TPM

[bronzeMe]

Describe the bug

The feature_mask seems unable to correctly configure whether to enable the hardware TPM，

According to the readme.md of the hyperenclave-driver, bit 8 indicates whether to turn off the fake TPM. However, even after setting bit 8 to 0, changing the feature_mask from 0x302 to 0x102, HyperEnclave still launched using the fake TPM.

To reproduce

...

Expected behavior

Starting hyperenclave using real hardware TPM

Logs

[1607662.972441] [76] tpm_detect starting....
[1607662.972441] [76] fake tpm is detected and initialized
[1607662.972441] [76] FAKE TPM: tpm signing key pub x
[1607662.972442] [76] C29974C9F1090FA4A10E9990620E91828B593A7211E2468450E3DC96DD5933FB
[1607662.972442] [76] size= :0x20
[1607662.972443] [76] FAKE TPM: tpm signing key pub y
[1607662.972443] [76] 402206ECCC5479289F33668EAAB85527ABBBB9F7B41CEB71551027D57AF28267
[1607662.972443] [76] size= :0x20
[1607662.972444] [76] FAKE TPM: root secret is generated and sealed
[1607662.972444] [76] FAKE TPM: hypervisor AK pub x=
[1607662.972444] [76] 3D9BB7BA028C5F97AC5AB1619336D9ED23E86858DDBDC23B510D5F0EBA8FF338
[1607662.972444] [76] size= :0x20
[1607662.972445] [76] FAKE TPM: hypervisor AK pub y=
[1607662.972445] [76] 0B28428BDA30B2800FCB032ABCED81071B5F0DCB1A02B22AFF56B7DD22E52522
[1607662.972445] [76] size= :0x20
[1607662.972445] [76] FAKE TPM: hash of he_ak_pub extended to PCR 13:
[1607662.972450] [76] AAA056CA1F030B7BD6C4089C2AEEC36D01173B46E0FD2B4C1BD2C14649B66539

Environment

test@test:~$ cat /etc/os-release
NAME="Ubuntu"
VERSION="20.04.6 LTS (Focal Fossa)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 20.04.6 LTS"
VERSION_ID="20.04"
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
VERSION_CODENAME=focal
UBUNTU_CODENAME=focal
test@test:~$ uname -a
Linux test 5.4.0-custom #1 SMP Thu Aug 22 05:22:55 UTC 2024 x86_64 x86_64 x86_64 GNU/Linux

Additional context

Possible solution/Implementation

https://github.com/asterinas/hyperenclave-driver/blob/master/driver/feature.c#L92

[Bonjourz]

Hi @bronzeMe , the bit index starts from 0.

Try to set the feature_mask to 0x202. Bit 8 is still be set in the 0x102.

By the way, it is not recommended to turn on the hardware TPM mode.