linux-kernel - Re: [PATCH] perf/x86: check ucode before disabling PEBS on SandyBridge

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Message-ID: <20120612180455.GB11413@one.firstfloor.org>
Date:	Tue, 12 Jun 2012 20:04:55 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Borislav Petkov <bp@...64.org>,
	Stephane Eranian <eranian@...gle.com>,
	Robert Richter <robert.richter@....com>,
	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
	andi@...stfloor.org, mingo@...e.hu, ming.m.lin@...el.com,
	Andreas Herrmann <andreas.herrmann3@....com>,
	Dimitri Sivanich <sivanich@....com>,
	Dmitry Adamushko <dmitry.adamushko@...il.com>
Subject: Re: [PATCH] perf/x86: check ucode before disabling PEBS on SandyBridge

> Also, you can create a pebs event while updating micro-code. There's a
> race window there if you don't check all cpus.

The best proposal I've seen so far was to track the minimum ucode
revision and check that on every syscall.

This can be a single global, so it should not be very exepsnive.

I can look at implementing that if that solution is agreeable with 
everyone.

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