linux-kernel - Re: [RFC PATCH 0/4] Alternative TPM patches for Trenchboot

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Message-ID: <3f7bb7d6-3410-4e04-b6fc-6fdc26274cfa@apertussolutions.com>
Date: Mon, 4 Nov 2024 19:13:13 -0500
From: "Daniel P. Smith" <dpsmith@...rtussolutions.com>
To: James Bottomley <James.Bottomley@...senPartnership.com>,
 Ard Biesheuvel <ardb@...nel.org>
Cc: Jarkko Sakkinen <jarkko@...nel.org>, x86@...nel.org,
 Ross Philipson <ross.philipson@...cle.com>,
 Thomas Gleixner <tglx@...utronix.de>, Peter Huewe <peterhuewe@....de>,
 Jason Gunthorpe <jgg@...pe.ca>,
 "open list:TPM DEVICE DRIVER" <linux-integrity@...r.kernel.org>,
 open list <linux-kernel@...r.kernel.org>, trenchboot-devel@...glegroups.com
Subject: Re: [RFC PATCH 0/4] Alternative TPM patches for Trenchboot

On 11/4/24 15:36, James Bottomley wrote:
> On Mon, 2024-11-04 at 11:34 -0500, Daniel P. Smith wrote:
> [...]
>> In case the question comes up from those not familiar, the kexec does
>> an GETSEC[SEXIT] which closes off access to Localities 1 and 2, thus
>> locking the DRTM PCR values. It brings the CPUs out of SMX mode so
>> the target kernel does not require to have any knowledge about
>> running in that mode.
> 
> So, to repeat the question: why a sysfs interface for setting the
> default locality?  If I understand correctly from what you say above,
> it can't be used in any kernel except the SL one, and that one could
> run permanently in it, so there's no requirement at all for user space
> to be able to change this, is there?

I responded to Ard this morning that, "If the slmodule is able to set 
the locality for all PCR extends coming from user space to be Locality 
2, that removes the current need for it." Where "it" is the sysfs node 
for default locality. This series does just that, so in a more direct 
response, no, a writable sysfs node is no longer needed with this series.

v/r
dps