On Tue, Oct 21, 2025 at 02:46:15PM +0200, Jan Kiszka wrote: > From: Jan Kiszka <[email protected]> > > As seen with optee_ftpm, which uses ms-tpm-20-ref [1], a TPM may write > the current time epoch to its NV storage every 4 seconds if there are > commands sent to it. The 60 seconds periodic update of the entropy pool > that the hwrng kthread does triggers this, causing about 4 writes per > requests. Makes 2 millions per year for a 24/7 device, and that is a lot > for its backing NV storage. > > It is therefore better to make the user intentionally enable this, > providing a chance to read the warning. > > [1] https://github.com/Microsoft/ms-tpm-20-ref > > Signed-off-by: Jan Kiszka <[email protected]>
Looking at DRBG_* from [1] I don't see anything you describe. If OPTEE writes NVRAM, then the implementation is broken. Also AFAIK, it is pre-seeded per power cycle. There's nothing that even distantly relates on using NVRAM. [1] https://trustedcomputinggroup.org/wp-content/uploads/TPM-2.0-1.83-Part-4-Supporting-Routines-Code.pdf BR, Jarkko
