Re: [PATCH v9 01/11] KEYS: trusted: Use get_random-fallback for TPM

[Jarkko Sakkinen <jarkko@kernel.org>]

On Thu, Mar 19, 2026 at 10:28:03AM -0400, Mimi Zohar wrote:
> On Wed, 2026-03-18 at 10:36 -0700, Chris Fenner wrote:
> > Apologies if my long message derailed this discussion. I meant to
> > support Mimi's concern here and project a future vision where
> > TCG_TPM2_HMAC doesn't conflict with other features.
> > 
> > More concisely, I think that:
> > 
> > > tpm2_get_random() is costly when TCG_TPM2_HMAC is enabled
> > 
> > is not a compelling argument for removing TPM as an RNG source,
> > because TCG_TPM2_HMAC is known to have poor performance already
> > anyway.
> 
> Agreed.  Thanks, Chris!  FYI, we raised concerns about IMA performance with the
> TPM HMAC and encrypted feature while it was being developed. James had some
> ideas, at the time, as to how to resolve the performance issue for IMA.  Yet it
> was upstreamed without those changes and with CONFIG_TCG_TPM2_HMAC enabled by
> default on x86 systems.
> 
> Jarkko has queued this patch in the "queue" branch, without indicating whether
> it will eventually be upstreamed or not.

Yes and there's been multiple months of time to comment this and I
backed up the patch set there, which is not same as applying it.

> 
> Mimi

BR, Jarkko