linux-kernel - Re: [PATCH 1/2] Fix perf LBR filtering

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Message-ID: <20130425170037.GD16732@two.firstfloor.org>
Date:	Thu, 25 Apr 2013 19:00:37 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Andi Kleen <andi@...stfloor.org>, mingo@...nel.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	eranian@...gle.com, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 1/2] Fix perf LBR filtering

> Traping the read deals with the first. The second shouldn't be a problem since
> we generally only allow kernel info for CAP_ADMIN; if we don't already for LBR
> that needs to be fixed separately.

Where is that check?  I don't see it.

Also remember that precise == 2 can enable LBR implicitly.

> That only leaves the third.. can we descern MMIO maps from the kernel page tables?

In theory you could use some bits in the PTE for vmalloc, but it would need quite a
few changes.

Also there may be corner cases where MMIO is in the direct mapping or in
the kernel mapping.


-Andi

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