linux-kernel - Re: [PATCH v6 1/4] sched/clock: interface to allow timestamps early in boot

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]

Message-ID: <20170927180548.GM17526@worktop.programming.kicks-ass.net>
Date:   Wed, 27 Sep 2017 20:05:48 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Dou Liyang <douly.fnst@...fujitsu.com>
Cc:     Pasha Tatashin <pasha.tatashin@...cle.com>, linux@...linux.org.uk,
        schwidefsky@...ibm.com, heiko.carstens@...ibm.com,
        john.stultz@...aro.org, sboyd@...eaurora.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, mingo@...hat.com, tglx@...utronix.de,
        hpa@...or.com
Subject: Re: [PATCH v6 1/4] sched/clock: interface to allow timestamps early
 in boot

On Wed, Sep 27, 2017 at 09:52:36PM +0800, Dou Liyang wrote:
> We do not want to do that. Because, we use "notsc" to support Dynamic
> Reconfiguration[1].
> 
> AFAIK, this feature enables hot-add system board which contains CPUs
> and memories. But the CPUs in different board may have different TSCs
> which are not consistent with the TSC from the existing CPUs. If we hot-add
> a board directly, the machine may happen the inconsistency of
> TSC.
> 
> We make our effort to specify the same TSC value as existing one through
> hardware and firmware, but it is hard. So we recommend to specify
> "notsc" option in command line for users who want to use Dynamic
> Reconfiguration.

Oh gawd, that's horrific. And in my book a good reason to kill that
option.