On Thu Sep 12, 2024 at 11:13 AM EEST, Roberto Sassu wrote:
> On Wed, 2024-09-11 at 18:14 +0300, Jarkko Sakkinen wrote:
> > On Wed Sep 11, 2024 at 11:53 AM EEST, Roberto Sassu wrote:
> > > I made few measurements. I have a Fedora 38 VM with TPM passthrough.
> >
> > I was thinking more like
> >
> > sudo bpftrace -e 'k:tpm_transmit { @start[tid] = nsecs; } kr:tpm_transmit { @[kstack, ustack, comm] = sum(nsecs - @start[tid]); delete(@start[tid]); } END { clear(@start); }'
> >
> > For example when running "tpm2_createprimary --hierarchy o -G rsa2048 -c owner.txt", I get:
>
> Sure:
Took couple of days to upgrade my BuildRoot environment to have bcc and
bpftrace [1] but finally got similar figures (not the same test but doing
extends).
Summarizing your results looking at call before tpm_transmit:
- HMAC management: 124 ms
- extend with HMAC: 25 ms
- extend without HMAC: 5.2 ms
I'd see the only possible way to fix this would be refactor the HMAC
implementation by making the caller always the orchestrator and thus
allowing to use continueSession flag for TPM2_StartAuthSession to be
used.
For example if you do multiple extends there should not be good reason
to setup and rollback session for each call separately right?
[1] https://codeberg.org/jarkko/linux-tpmdd-test
BR, Jarkko
