linux-kernel - Re: [PATCH 1/5] Add a global synchronization point for pvclock

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: <1271673975.1674.763.camel@laptop>
Date:	Mon, 19 Apr 2010 12:46:15 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Avi Kivity <avi@...hat.com>
Cc:	Glauber Costa <glommer@...hat.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Zachary Amsden <zamsden@...hat.com>
Subject: Re: [PATCH 1/5] Add a global synchronization point for pvclock

On Sat, 2010-04-17 at 21:48 +0300, Avi Kivity wrote:
> > After this patch is applied, I don't see a single warp in time during 5 days
> > of execution, in any of the machines I saw them before.
> >
> >    
> 
> Please define a cpuid bit that makes this optional.  When we eventually 
> enable it in the future, it will allow a wider range of guests to enjoy it.

Right, so on x86 we have:

X86_FEATURE_CONSTANT_TSC, which only states that TSC is frequency
independent, not that it doesn't stop in C states and similar fun stuff.

X86_FEATURE_TSC_RELIABLE, which IIRC should indicate the TSC is constant
and synced between cores.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/