linux-kernel - Re: [regression] significant delays when secureboot is enabled since 6.10

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Message-Id: <D45HXRJ0LTFC.3VVF6QI3NGVXV@kernel.org>
Date: Sat, 14 Sep 2024 01:06:28 +0300
From: "Jarkko Sakkinen" <jarkko@...nel.org>
To: "Jarkko Sakkinen" <jarkko.sakkinen@....fi>, "Roberto Sassu"
 <roberto.sassu@...weicloud.com>, "James Bottomley"
 <James.Bottomley@...senPartnership.com>, "Linux regressions mailing list"
 <regressions@...ts.linux.dev>
Cc: <keyrings@...r.kernel.org>, "linux-integrity@...r.kernel.org"
 <linux-integrity@...r.kernel.org>, "LKML" <linux-kernel@...r.kernel.org>,
 "Pengyu Ma" <mapengyu@...il.com>
Subject: Re: [regression] significant delays when secureboot is enabled
 since 6.10

On Fri Sep 13, 2024 at 11:50 PM EEST, Jarkko Sakkinen wrote:
> 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

Note that the timings are accumulated (not averaged). It would be easy
to fix this tho.

BR, Jarkko