linux-kernel - Re: [PATCH 1/3] tpm: Disable TCG_TPM2

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Date: Wed, 22 May 2024 17:13:41 +0300
From: "Jarkko Sakkinen" <jarkko@...nel.org>
To: "James Bottomley" <James.Bottomley@...senPartnership.com>, "Vitor
 Soares" <ivitro@...il.com>, <linux-integrity@...r.kernel.org>
Cc: <keyrings@...r.kernel.org>, "Peter Huewe" <peterhuewe@....de>, "Jason
 Gunthorpe" <jgg@...pe.ca>, "Mimi Zohar" <zohar@...ux.ibm.com>, "David
 Howells" <dhowells@...hat.com>, "Paul Moore" <paul@...l-moore.com>, "James
 Morris" <jmorris@...ei.org>, "Serge E. Hallyn" <serge@...lyn.com>,
 <linux-kernel@...r.kernel.org>, <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH 1/3] tpm: Disable TCG_TPM2_HMAC by default

On Wed May 22, 2024 at 4:35 PM EEST, James Bottomley wrote:
> On Wed, 2024-05-22 at 09:18 +0100, Vitor Soares wrote:
> > On Tue, 2024-05-21 at 08:33 -0400, James Bottomley wrote:
> > > On Tue, 2024-05-21 at 10:10 +0300, Jarkko Sakkinen wrote:
> > > > This benchmark could be done in user space using /dev/tpm0.
> > > 
> > > Let's actually try that.  If you have the ibmtss installed, the
> > > command to time primary key generation from userspace on your tpm
> > > is
> > > 
> > > time tsscreateprimary -hi n -ecc nistp256
> > > 
> > > 
> > > And just for chuckles and grins, try it in the owner hierarchy as
> > > well (sometimes slow TPMs cache this)
> > > 
> > > time tsscreateprimary -hi o -ecc nistp256
> > > 
> > > And if you have tpm2 tools, the above commands should be:
> > > 
> > > time tpm2_createprimary -C n -G ecc256
> > > time tpm2_createprimary -C o -G ecc256
> > > 
> > > James
> > > 
> > > 
> > 
> > Testing on an arm64 platform I get the following results.
> > 
> > hmac disabled:
> >   time modprobe tpm_tis_spi
> >   real    0m2.776s
> >   user    0m0.006s
> >   sys     0m0.015s
> > 
> >   time tpm2_createprimary -C n -G ecc256
> >   real    0m0.686s
> >   user    0m0.044s
> >   sys     0m0.025s
> > 
> >   time tpm2_createprimary -C o -G ecc256
> >   real    0m0.638s
> >   user    0m0.048s
> >   sys     0m0.009s
> > 
> > 
> > hmac enabled:
> >   time modprobe tpm_tis_spi
> >   real    8m5.840s
> >   user    0m0.005s
> >   sys     0m0.018s
> > 
> > 
> >   time tpm2_createprimary -C n -G ecc256
> >   real    5m27.678s
> >   user    0m0.059s
> >   sys     0m0.009s
> > 
> >   (after first command)
> >   real    0m0.395s
> >   user    0m0.040s
> >   sys     0m0.015s
> > 
> >   time tpm2_createprimary -C o -G ecc256
> >   real    0m0.418s
> >   user    0m0.049s
> >   sys     0m0.009s
>
> That's interesting: it suggests the create primary is fast (as
> expected) but that the TPM is blocked for some reason.  Is there
> anything else in dmesg if you do
>
> dmesg|grep -i tpm
>
> ?
>
> Unfortunately we don't really do timeouts on our end (we have the TPM
> do it instead), but we could instrument your kernel with command and
> time sent and returned.  That may tell us where the problem lies.

If there was possibility to use bpftrace it is trivial to get histogram
of time used where. I can bake a script but I need to know first if it
is available in the first place before going through that trouble.

BR, Jarkko