From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Thu, 25 Apr 2013 19:18:42 +0200 From: Peter Zijlstra To: Andi Kleen Cc: mingo@kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, eranian@google.com, Andi Kleen Subject: Re: [PATCH 1/2] Fix perf LBR filtering Message-ID: <20130425171842.GA8669@dyad.programming.kicks-ass.net> References: <1366844694-2770-1-git-send-email-andi@firstfloor.org> <20130425162535.GA5828@dyad.programming.kicks-ass.net> <20130425164100.GC16732@two.firstfloor.org> <20130425164837.GD5828@dyad.programming.kicks-ass.net> <20130425170037.GD16732@two.firstfloor.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130425170037.GD16732@two.firstfloor.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: On Thu, Apr 25, 2013 at 07:00:37PM +0200, Andi Kleen wrote: > > 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. Then that might need fixing. > Also remember that precise == 2 can enable LBR implicitly. Sure.. but it doesn't need the filter stuff. Now I completely forgot if it will actually still use the filter muck.. /me goes check I think intel_pmu_lbr_filter() will typically bail on the X86_BR_ALL test for PEBS fixup, it might only end up in the filter code if precise_br_compat() finds another LBR user compatible with the fixup. > > 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. Hrmm... do we keep track of the MMIO regions somewhere at all?