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

James Bottomley
2024-09-15T15:00:51Z

On Sun, 2024-09-15 at 17:50 +0300, Jarkko Sakkinen wrote:
> On Sun Sep 15, 2024 at 4:59 PM EEST, James Bottomley wrote:
> > On Sun, 2024-09-15 at 13:07 +0300, Jarkko Sakkinen wrote:
> > > On Sun Sep 15, 2024 at 12:43 PM EEST, Jarkko Sakkinen wrote:
> > > > When it comes to boot we should aim for one single
> > > > start_auth_session during boot, i.e. different phases would
> > > > leave that session open so that we don't have to load the
> > > > context every single time.  I think it should be doable.
> > >
> > > The best possible idea how to improve performance here would be
> > > to transfer the cost from time to space. This can be achieved by
> > > keeping null key permanently in the TPM memory during power
> > > cycle.
> >
> > No it's not at all.  If you look at it, the NULL key is only used
> > to encrypt the salt for the start session and that's the operating
> > taking a lot of time.  That's why the cleanest mitigation would be
> > to save and restore the session.  Unfortunately the timings you
> > already complain about still show this would be about 10x longer
> > than a no-hmac extend so I'm still waiting to see if IMA people
> > consider that an acceptable tradeoff.
>
> The bug report does not say anything about IMA issues. Please read
> the bug reports before commenting ;-) I will ignore your comment
> because it is plain misleading information.
>
> https://bugzilla.kernel.org/show_bug.cgi?id=219229

Well, given that the kernel does no measured boot extends after the EFI
boot stub (which isn't session protected) finishes, what's your theory
for the root cause?

James