linux-kernel - Re: [PATCH] x86: Export tsc related information in sysfs

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Message-ID: <1274183935.5605.7726.camel@twins>
Date:	Tue, 18 May 2010 13:58:54 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Arjan van de Ven <arjan@...radead.org>,
	Dan Magenheimer <dan.magenheimer@...cle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Venkatesh Pallipadi <venki@...gle.com>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	chris.mason@...cle.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: Export tsc related information in sysfs

On Tue, 2010-05-18 at 13:25 +0200, Andi Kleen wrote:
> On Tue, May 18, 2010 at 11:58:18AM +0200, Peter Zijlstra wrote:
> > On Sun, 2010-05-16 at 22:06 -0700, Arjan van de Ven wrote:
> > > look we're not disabling ring 3 tsc. We could, but we don't.
> > 
> > Maybe we should.
> 
> That would kill the vsyscall too. Remember it's running in ring 3.
> 
> That is in theory you could disable it on systems where the vsyscall
> doesn't use it, but then you would likely break huge amounts of software, 
> unless you emulate it.

Well, software shouldn't use it, so breaking it sounds like a fine
idea ;-)

Also, a slow emulation is an incentive to actually do the right thing.
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