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: <alpine.DEB.2.11.1602241200020.3670@nanos>
Date:	Wed, 24 Feb 2016 12:00:31 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	"Christopher S. Hall" <christopher.s.hall@...el.com>
cc:	richardcochran@...il.com, mingo@...hat.com, john.stultz@...aro.org,
	hpa@...or.com, jeffrey.t.kirsher@...el.com, x86@...nel.org,
	linux-kernel@...r.kernel.org, intel-wired-lan@...ts.osuosl.org,
	netdev@...r.kernel.org, kevin.b.stanton@...el.com,
	kevin.j.clarke@...el.com
Subject: Re: [PATCH v8 6/8] x86: tsc: Always Running Timer (ART) correlated
 clocksource

On Mon, 22 Feb 2016, Christopher S. Hall wrote:

> On modern Intel systems TSC is derived from the new Always Running Timer
> (ART). ART can be captured simultaneous to the capture of
> audio and network device clocks, allowing a correlation between timebases
> to be constructed. Upon capture, the driver converts the captured ART
> value to the appropriate system clock using the correlated clocksource
> mechanism.
> 
> On systems that support ART a new CPUID leaf (0x15) returns parameters
> “m” and “n” such that:
> 
> TSC_value = (ART_value * m) / n + k [n >= 2]
> 
> [k is an offset that can adjusted by a privileged agent. The
> IA32_TSC_ADJUST MSR is an example of an interface to adjust k.
> See 17.14.4 of the Intel SDM for more details]
> 
> Signed-off-by: Christopher S. Hall <christopher.s.hall@...el.com>
> [jstultz: Tweaked to fix build issue, also reworked math for
> 64bit division on 32bit systems]
> Signed-off-by: John Stultz <john.stultz@...aro.org>

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ