Re: [PATCH 2/3] x86, perf: Support custom test values for extra_regs

From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH 2/3] x86, perf: Support custom test values for extra_regs
Date	2015-06-30 13:20 +0200
Message-ID	<pH1K1-ax-3@gated-at.bofh.it> (permalink)
References	<pGOMT-6LO-79@gated-at.bofh.it> <pGOMU-6LO-95@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Mon, Jun 29, 2015 at 02:22:14PM -0700, Andi Kleen wrote:
> From: Andi Kleen <ak@linux.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?
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[PATCH 2/3] x86, perf: Support custom test values for extra_regs Andi Kleen <andi@firstfloor.org> - 2015-06-29 23:30 +0200
  Re: [PATCH 2/3] x86, perf: Support custom test values for extra_regs Peter Zijlstra <peterz@infradead.org> - 2015-06-30 13:20 +0200

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