linux-kernel - Re: [PATCH 2/3] x86, perf: Support custom test values for extra

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Date:	Tue, 30 Jun 2015 08:44:51 -0700
From:	Andi Kleen <ak@...ux.intel.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Andi Kleen <andi@...stfloor.org>, eranian@...gle.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] x86, perf: Support custom test values for extra_regs

On Tue, Jun 30, 2015 at 01:19:07PM +0200, Peter Zijlstra wrote:
> On Mon, Jun 29, 2015 at 02:22:14PM -0700, Andi Kleen wrote:
> > From: Andi Kleen <ak@...ux.intel.com>
> > 
> > Current kernels always test extra registers at boot with RMW
> > cycle, to catch lying virtual machines.
> > 
> > For a new register the standard 0x1ff test value does not work,
> > as 0x1ff is not a valid value and causes an #GP.
> > 
> > Add the ability to add custom test values to an extra_reg
> > into the description tables.
> 
> Just wondering; is there not a test value that works for all registers?

0x11 will likely work everywhere.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only
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