linux-kernel - [PATCH 0/3] x86/platform/UV: Update TSC support

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-next>] [day] [month] [year] [list]

Date:   Thu, 21 Sep 2017 15:12:21 -0500
From:   <mike.travis@....com>
To:     Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Bin Gao <bin.gao@...ux.intel.com>,
        Prarit Bhargava <prarit@...hat.com>,
        Dimitri Sivanich <dimitri.sivanich@....com>,
        Andrew Banman <andrew.banman@....com>,
        Russ Anderson <russ.anderson@....com>,
        linux-kernel@...r.kernel.org, x86@...nel.org
Subject: [PATCH 0/3] x86/platform/UV: Update TSC support

The UV BIOS goes to considerable effort to get the TSC synchronization
accurate across the entire system.  Included in that are multiple
chassis that can have 32+ sockets.  The architecture also supports an
external high resolution clock to help all the chassis and CPU's in
maintaining this synchronization.

As a result the UV system BIOS provides much better TSC accuracy than
the current kernel TSC ADJUST functions.  This is extremely important in
applications that, for example, store and access data bases.

These two patches disable an assumption made by the kernel TSC ADJUST
functions that are not applicable to the UV system (and maybe others?).
That being that Socket 0 in the system should have a TSC ADJUST value
of zero.  This is incorrect when all the chassis are started asynchronously
to each other, therefore which TSC's are farther advanced is not predictable.
The UV BIOS deals with this scenario correctly.

--