linux-kernel - Re: [RFC 0/2] i2c-designware: Add support for AMD PSP semaphore

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 27 Dec 2021 08:00:09 +0100
From:   Jan Dąbroś <jsd@...ihalf.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Hans de Goede <hdegoede@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-i2c <linux-i2c@...r.kernel.org>,
        Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Wolfram Sang <wsa@...nel.org>,
        Raul E Rangel <rrangel@...omium.org>,
        Marcin Wojtas <mw@...ihalf.com>,
        Grzegorz Jaszczyk <jaz@...ihalf.com>, upstream@...ihalf.com
Subject: Re: [RFC 0/2] i2c-designware: Add support for AMD PSP semaphore

sob., 25 gru 2021 o 16:59 Andy Shevchenko <andy.shevchenko@...il.com>
napisał(a):
>
> On Thu, Dec 23, 2021 at 4:43 PM Jan Dabros <jsd@...ihalf.com> wrote:
> >
> > This patchset comprises support for new i2c-designware controller setup on some
> > AMD Cezanne SoCs, where x86 is sharing i2c bus with PSP. PSP uses the same
> > controller and acts as an i2c arbitrator there (x86 is leasing bus from it).
> >
> > First commit aims to improve generic i2c-designware code by adding extra locking
> > on probe() and disable() paths. I would like to ask someone with access to
> > boards which use Intel BayTrail(CONFIG_I2C_DESIGNWARE_BAYTRAIL) to verify
> > behavior of my changes on such setup.
> >
> > Second commit adds support for new PSP semaphore arbitration mechanism.
> > Implementation is similar to the one from i2c-designware-baytrail.c however
> > there are two main differences:
> > 1) Add new ACPI ID in order to protect against silent binding of the old driver
> > to the setup with PSP semaphore. Extra flag ARBITRATION_SEMAPHORE added to this
> > new _HID allows to recognize setup with PSP.
> > 2) Beside acquire_lock() and release_lock() methods we are also applying quirks
> > to the lock_bus() and unlock_bus() global adapter methods. With this in place
> > all i2c clients drivers may lock i2c bus for a desired number of i2c
> > transactions (e.g. write-wait-read) without being aware of that such bus is
> > shared with another entity.
> >
> > Mark this patchset as RFC, since waiting for new ACPI ID value. As a temporary
> > measure use "AMDI9999". Once proper one will be ready, will re-send this CL for
> > review & merge.
> >
> > Looking forward to some feedback.
>
> When you will be ready, CC a new version also to Hans, he may look at
> it from the Baytrail functionality perspective.

Thanks for the hint, it will be very helpful to have this tested on
Baytrail. From other comments on this RFC it seems that I would need
to affect Baytrail-semaphore path even more than initially thought.

Best Regards,
Jan